Search Results: Tonya McKay

By Tonya McKay · Published June 25, 2012

Pantothenic acid, Vitamin B5

Panthenol is a popular ingredient for both skin and hair care products. Hair care products that use this ingredient are said to have enhanced moisturization effects and add thickness or body to the hair. Proctor and Gamble has built their entire Pantene Pro-V line of products to capitalize on the properties of this ingredient. There seems to be a bit of confusion, however, about the role of panthenol in a formulation and whether or not it is beneficial or possibly even harmful for curly hair. A closer look at the chemistry of panthenol should provide clarification about this ingredient.

The Basic Chemistry

Panthenol is a derivative of vitamin B5 (pantothenic acid”> and is known as a provitamin. Panthenol is what is called a chiral molecule, or one that has a molecular structure that gives it a “handedness,” either right-handed (dextrorotatory”> or left-handed (levorotatory”>. These two mirror-image enantiomers are not superimposable on one another, in the same manner in which your two hands are mirror images of one another rather than exact duplicates. Oftentimes, the two versions of a molecule have differing chemical or biological properties. For cosmetic purposes, panthenol is supplied either as a racemic mixture (50/50″> of both types of enantiomers or as the purified “D” version. This is most relevant in skin care applications, as the D-version of panthenol is the biologically active version.

The Properties

The multiple hydroxyl (-OH”> groups on the panthenol molecule impart most of the physical properties to it, most particularly its high solubility in water and other solvents. Panthenol is a highly effective humectant, a class of ingredients used in skin and hair care products to promote moisture-retention. It has a highly hydrophilic and hygroscopic chemical structure which attracts water from the atmosphere and binds it to various sites along the molecule. Humectants typically possess multiple alcohol (hydroxyl”> or similarly hydrophilic sites (such as ethers or ammonium groups”>, which are available for hydrogen bonding with water molecules. Hydrogen bonding between humectants and water aids in moisture-retention by minimizing water loss due to evaporation.

Panthenol is not only a humectant, but is also a useful moisturizer and emollient. It spreads evenly on the surface of hair strands, forming a smooth film on the surface of the cuticle. This film gives enhanced coherence to the reflection of light from the surface of the hair, which imparts significant gloss and shine. The smooth film also provides excellent slip between adjacent strands of hair and detangling properties. Panthenol is capable of penetrating the cuticle and entering the hair shaft as well, where it aids in moisture retention and provides volume.

It is important to note that sometimes penetration of the shaft by ingredients can create a rough cuticle surface and lead to frizz, due to swelling of the hair shaft. This may not occur for everyone and is dependent upon several factors, including porosity of the hair and the amount of the ingredient used in the product. It is a potential undesirable effect, so keep this in the back of your mind when using a product containing the ingredient.

Although there is a persistent rumor that panthenol creates waxy buildup on hair, there is no evidence to support such an assertion. Panthenol is not at all similar in structure to waxy materials. It is also extremely water soluble, alcohol soluble, mildly soluble in glycerin and is fairly easily capable of being mixed into most oils. Additionally, panthenol has no component to its chemical structure that would cause it to bind tightly to the surface of a hair strand. For these reasons, it should be easily removed from hair by rinsing, washing with mild shampoo and even conditioner cleansing. If one is experiencing problems with build up and unpleasant hair texture when using a product containing panthenol, the issue is more likely due to other ingredients in the formulation.

Panthenol is readily absorbed by skin, and as the precursor of vitamin B5, it directly impacts metabolic processes in epidermal cells. It has been found to have many beneficial properties for epithelial tissue, including increased hydration and improved elasticity and is believed to promote cell regeneration. When used in shampoos and conditioners, panthenol conceivably provides added benefit by improving scalp health and potentially improving hair growth.

Final Thoughts

Panthenol is a naturally-occurring material that adds several beneficial properties to hair care formulations. It is a humectant, emollient, glossifier, detangler and moisturizing agent. It is highly water soluble and is also easily removable with mild plant-derived oils or via conditioner cleansing. When selecting humectant-containing products, one must keep in mind the climate in which they live, how that impacts hair and how they might expect a humectant to contribute to the overall performance of their own hair within the constraints of that climate. Also, depending upon the porosity of your hair and the type of product being used, you may experience a roughened hair texture or some frizz due to penetration of the hair shaft. If this should happen, it might be best to discontinue use or to decrease use of the product. Finally, experimentation is the best way to find out what works well on your own hair.

By Tonya McKay · Published April 4, 2012

Occasionally discussions arise in the hair product-focused community concerning several cationic surfactants, such as cetrimonium chloride, behentrimonium methosulfate and stearamidopropyl dimethylamine.

For good reason, the INCI (International Nomenclature of Cosmetics Ingredients”> names of these molecules are often confused with silicones, sulfate detergents and preservatives. It can be surprising to hear that a “sulfate” is a desirable conditioning agent for many people. A brief review of the different types of surfactants and their various applications, as well as a closer examination of cationic surfactants in particular seems useful to bring some clarity to the confusion.

What are Surfactants?

Surfactants are molecules that possess dual-polarity, having both hydrophobic (water hating”> and hydrophilic (water loving”> segments. Although hydrophobic is the term most often used to describe non-polar substances, the term lipophilic (oil loving”> is perhaps a more accurate descriptor, because they do not so much hate water as they prefer oils. The unique quality of being both lipophilic and hydrophilic is described as being amphiphilic. Molecules that are amphiphilic characteristically possess a long segment that is a non-polar hydrocarbon chain and a polar head group that can be ionically-charged or not.

Due to the uniquely polar properties of water, immersion of an amphiphilic molecule in an aqueous solution results in very interesting behavior.  Water molecules have strong intermolecular hydrogen bonding that creates a predictable geometric structure within the bulk of the liquid. This hydrogen bonding forms a tightly stretched molecular film at the interface between air and the liquid.  This gives water its characteristically high surface tension. Placing a molecule with hydrophobic properties into that environment disturbs that local structure, so the water excludes the hydrophobic molecule from the solution by pushing it to the surface.

You have certainly witnessed this yourself when you have seen the rainbow display of oil on the surface of a water puddle. What happens when the molecule has both a hydrophilic portion and a hydrophobic portion is that the polar head group is solvated into the solution just below the air-water interface, while the hydrophobic tail group juts out above the surface. This disrupts the hydrogen bonding at the surface of the water, which substantially decreases the surface tension.  For this reason, amphiphilic molecules are said to be “surface active agents” and are called surfactants.

Eventually, if the concentration of amphiphilic material is increased, the surface of the solution becomes saturated, and an intriguing phenomenon occurs.  In order to preserve as much of the polar structure of water as possible, the amphiphile molecules aggregate together into tiny spheres in the bulk of the solution, with the hydrophobic portions clustered in the center of the sphere, which is surrounded by a hydration shell comprised of the polar head group.  These amazing aggregates are called micelles, and are the foundation for many biological functions.  They are also useful for many functions such as cleansing, emulsion stabilization, targeted and/or controlled release drug delivery, formation of liquid crystalline structures and many other applications.

Types of Surfactants

Surfactant molecules are classified according to the ionic charge of the hydrophilic head group.  These classes consist of anionic, cationic, nonionic, and zwitterionic surfactants. The ionic surfactants are available in salt form with an appropriate alkali metal or ammonium counterion.  Nonionic surfactants typically possess several repeat units of ethylene oxide as the hydrophilic moiety. Dual-charged (zwitterionic”> surfactants also have utility in hair care products.  Many polymers have amphiphilic qualities as well, and they are quite interesting in their properties.  However, in this discussion, for the sake of brevity and focus, we shall confine our examination of surfactants to those which are small molecules, and exclude discussion of polymeric surfactants.

Anionic surfactants, such as sodium lauryl sulfate, ammonium laureth sulfate and sodium cocoyl isethionate carry a negative charge on the polar head group.  These materials are typically incorporated into shampoo formulations for their detergency properties.  They are highly effective at removing dirt and oil from the hair and scalp.  Many consumers with delicate, curly hair find these to be too drying and damaging for frequent use, and they either seek shampoos with different types of surfactants or opt to use cleansing conditioners.

Nonionic surfactants are those such as decyl glucoside and  PEG-10 laurate, which have no residual electric charge at all.  These surfactants can perform a variety of functions in a formula, such as emulsion stabilization, mild detergency and viscosity modification.

Zwitterionic (or amphoteric”> surfactants are dual-charged (have both a positive and negative charge on the molecule”>. Many display pH-dependent charge behavior, having one charge at lower pH’s and the opposite charge at higher pH’s. These types of surfactants, such as cocamidopropyl betaine, are valued for being mild both to skin and hair.  They also provide foam-boosting to shampoos that contain anionic surfactants, which enhances lather, a property preferred by many consumers.

Cationic surfactants such as cetrimonium chloride and stearamidopropyl dimethylamine, have a positive charge on their head group.  The composition of the molecules can vary, but is typically a fatty, acid-derived, hydrophobic tail with a nitrogen-containing head group.  The nitrogen-containing group can be either a tertiary or quaternary amine.  Typically these surfactants are either alkyl amine salts or alkyl quaternary ammonium salts.

Overall, cationic surfactants contribute many excellent properties to both shampoos and conditioners.

What Sets Cationic Surfactants Apart

Cationic surfactants, as their counterparts, are quite versatile, due to their amphiphilic character.  However, rather than being used primarily for detergency, cationic surfactants are more often used for very different applications, especially in hair care products. Perhaps the most important use for cationic surfactants in hair care is as conditioning agents.

You may recall that the surface of hair has an overall negative charge, which becomes more prevalent if the cuticle is damaged.  The head groups of these cationic surfactants experience electrostatic attraction to these negatively-charged sites and adsorb onto the surface of the hair.  The hydrophobic portion of the surfactant molecule lies flat along the surface of the hair, forming a film that smoothes the cuticle.  This film has multiple effects, including reduction of static, reduction of combing forces, increase in pleasing tactile feel of the hair, and a decrease in tangle formation.  Cationic surfactants used for these purposes have also been found to aid in color retention for artificially dyed hair.

Alkyl quaternary ammonium salts, such as cetrimonium chloride and behentrimonium methosulfate have been found to build up on the surface of hair after multiple uses.  They can be rather difficult to remove once this happens.  They are also incompatible with anionic surfactants in shampoos, as they form an insoluble complex in the solution.  Another undesirable property for use in shampoos is that they depress the foaming ability in such formulae.  For this reason, they are most preferred in conditioning products.

Alkyl amine salts, such as stearamidopropyl dimethylamine actually adsorb onto the surface of the hair to a lesser extent than he quaternary compounds.  They are also more easily rinsed and removed, and thus have less incidence of undesired accumulation.  Alkyl amines can be neutralized into a salt via addition of small amounts of weak acids, such as citric, lactic, or propionic to form the corresponding ester (stearamidopropyl dimethylamine lactate”>.  These neutral salts are quite compatible with anionic surfactants and do not interfere with foam formation, rendering them quite suitable for use in conditioning shampoos.

Cationic surfactants are also quite useful for the emulsification and solubilization of hydrophobic additives, such as silicones.  They achieve this by encapsulating the non-polar material inside the interior of their micellar structures.  Once the solution is diluted by water in the shower, the micelle structures break down, facilitating deposition of the conditioning agent onto the surface of the hair.  This enables them to perform multiple functions in the same formula; emulsion stabilizer as well as conditioning agent.

Overall, cationic surfactants contribute many excellent properties to both shampoos and conditioners.  They can be effective mild cleansers in a conditioner, due to their surfactant structure, but their most valuable contribution is as film-forming conditioning agents. They are water soluble, but the quaternary variety bind rather tightly to the hair surface and can build up, so be aware of the potential for that issue.  The alkyl amines seem to have no significant drawbacks for a curly girl or guy, and many users report enjoying their effects.

Quick Round-Up

Alkyl-quaternized ammonium salts:

• Stearalkonium chloride
• Cetrimonium chloride
• Cetrimonium bromide
• Behentrimonium methosulfate
• Behentrimonium chloride
• Benzalkonium chloride
• Cinnamidopropyltrimonium chloride
• Cocotrimonium chloride
• Dicetyldimonium chloride
• Dicocodimonium chloride
• Hydrogenated Palm Trimethylammonium chloride
• Lauryltrimonium chloride
• Quaternium-15
• Quaternium-22

Alkyl amines or amine salts:

• Stearamidopropyl dimethylamine (lactate, citrate, propionate”>
• Isostearamidopropyl dimethylamine
• Isostearamidopropyl morpholine
• Wheatgermamidopropyl dimethylamine
• Behenamidopropyl dimethylamine

By Tonya McKay · Published March 6, 2012

Celebrity stylist Chaz Dean professes a passion for ensuring his clients have healthy, beautiful hair. Over the course of his years working in the beauty industry, he developed the opinion that most commercially-available shampoo was counterproductive to this goal, and as a result, has not used it on either himself or clients in over 14 years. However, this doesn’t mean that Chaz prefers dirty hair.

He claims that there is a gentler way to achieve silky, clean tresses using oils, conditioning agents and nonionic surfactants to dissolve and gently remove oils and dirt from the scalp and hair. Using skills honed in a previous product development project, he designed a system of cleansing that his marketing material proclaims to be a “revolutionary new concept.” The result is the highly successful WEN hair care product line, founded upon the concept of a sulfate-free, non-foaming, cleansing and moisturizing conditioner.

This is certainly not a novel concept for those familiar with the “Curly Girl” or no-shampoo methods. Many have been doing this for years with all sorts of products designed specifically to be conditioners rather than cleansers. There are also products by companies such as DevaCurl and Jessicurl that market cleansers that are either no or low-shampoo. What is fairly unique about the WEN products, however, is the sheer amount of mass marketing and mainstream publicity Chaz Dean has been able to garner, particularly through his use of QVC as a publicity and sales tool.

The WEN products are fairly pricey and come with pretty specific instruction for use. In these formulas, nonionic surfactants work together with conditioning agents to help dissolve and remove sebum, product residue and environmental contaminants from the hair.

Dean recommends that a fairly large quantity of the product be applied at the roots and worked down into the hair. The number of squirts he says to use varies with hair length. Once the hair is saturated, he prescribes a dash of water be added followed by gentle hand washing.

For maximum cleansing and moisturizing, he then says the product should remain on the hair for the duration of the shower prior to rinsing. Users are then instructed to apply a final dollop to wet, rinsed hair from the midpoint to the ends for additional conditioning, shine and protection.

So how do Dean’s cleansers stack up against other shampoos, low-poos and no-poos? An examination of the ingredients should reveal a significant amount of information. There are several main categories of ingredients in his cleansing products: emollients and conditioning agents, emulsifiers, humectants, botanical extracts and other additives.

Emollients and Conditioning Agents

An emollient or conditioning agent forms a protective film over the surface of hair or skin, which adds gloss and shine to the hair, protects the hair from water loss to the environment (occlusion”>, and helps adjacent strands slide easily against one another. This all helps to reduce combing forces, facilitates detangling and prevents damage incurred by snarls. Conditioning agents can sometimes also act as humectants, attracting water to the hair.

Some examples of familiar conditioning agents include dimethicone, polyquaternium-10, dimethicone copolyol, amodimethicone, shea butter, jojoba oil, fatty alcohols, many proteins, hydrolyzed proteins, coconut oil, mineral oil, petrolatum, small molecule cationic surfactants and alkyl esters.

Below is a specific list of emollients found in the WEN cleaning products.

• Cetyl alcohol and cetearyl alcohol are fatty alcohols used as emollients that can help smooth the cuticle of the hair.  They also function as viscosity  modifiers, opacifiers and emulsion stabilizers.
• Plant-derived oils such as shea butter, jojoba oil, coconut oil, sweet almond oil and avocado oil are highly effective and nourishing emollients.
• Amodimethicone is an amine-functionalized silicone polymer that aids in color retention, smoothes, conditions and adds high gloss to the hair.  This particular silicone polymer, while water insoluble, has been found to resist accumulation via build up on the hair surface, even with repeated use.
• Stearamidopropyl dimethylamine is a tertiary amine surfactant used as a film former that can smooth the cuticle and reduce friction and combing forces.
• PEG-60 almond glycerides is a useful emulsifying ingredient that possesses mild conditioning properties.
• Guar hydroxypropyltrimonium chloride is a cationic polymer that provides excellent moisturization and conditioning properties via adsorption onto the surface of the hair.
• Dicetyldimonium chloride is a small molecule cationic surfactant that provides mild conditioning to hair via adsorption.
• Hydrolyzed wheat protein can provide protection and conditioning to hair via film formation at the surface and also via penetration into the cortex of the hair.  People with certain hair types enjoy the results of this better than others.

Emulsifiers

Emulsifying agents (also known as surfactants”> are materials, which have amphiphilic character, meaning they are both water-loving (hydrophilic”> and oil-loving (lipophilic”>. This special property enables them to be used to create and stabilize oil-in-water and water-in-oil mixtures known as emulsions. The WEN formulas rely upon nonionic surfactants for this job, and they are effective at dispersing the non-water soluble materials in his products.

• Ceteareth-20: This is a mixture of ethoxylated fatty acids (cetyl- and stearyl-“> that is a nonionic surfactant typically used as an emulsion stabilizer.
• Polysorbate 60 is an ethoxylated sorbitan derivative that is a nonionic surfactant used as an emulsifier.

Humectants

Humectants are materials that contain water-attracting elements, typically oxygen in hydroxyl and carbonyl groups. Some of these liquids can also act as solvents for some materials that are less soluble in water.

• Glycerin is a moisturizing humectant that also imparts a thick, velvety texture to a product.
• Panthenol is a pro-vitamin that is a highly effective humectant.
• Butylene glycol is a humectant and also a co-solvent.

The remainder of the ingredients is a mixture of botanical extracts that adds little to the function of the product, fragrance, mild acids or bases for pH adjustment and preservatives.

Mainstream Haircare

The mainstream cosmetics and hair care industry is still mystified by the aversion many are developing to the use of synthetic surfactant-heavy shampoos. However, the success of products such as these might send a message to the larger companies that there is a large sector of the market that desires something different for their hair.

The main criticism of these products from a formulator’s perspective is that the ingredients list does not seem to adhere to INCI labeling standards for hair and skin care products. This makes it difficult at first glance to determine the approximate proportion of each ingredient listed. It is important if one desires credibility in this industry to strive to maintain labels that are clear and follow standard protocol.

Final Thoughts

Overall, Chaz Dean’s conditioning cleansers look to be capable of providing the same level of cleansing as many other conditioners and no-poo products designed for the same purpose. The inclusion of amodimethicone, guar hydroxypropylytrimonium chloride, fatty alcohols and small molecule cationic surfactants indicates that the product should impart a significant amount of conditioning properties to the hair as well, so it should be able to replace the need for multiple products.

The quality of the ingredients seems to be superior to most very inexpensive drug-store conditioners often relied upon for conditioner washing. However, whether WEN cleansing conditioners provide as much benefit as one would hope when considering the price remains to be seen by this curly chemist.

What has your own experience been?

By Tonya McKay · Published February 3, 2012

One of the many conundrums in the world of curly hair is that some people experience a relaxation of their curls as their hair gains length, while others experience the converse: their curl increases with the length of their hair.

The former trend makes sense without having to give it much thought. Longer hair has more weight and is pulled down by gravity, which lengthens and loosens the curl. However, the latter phenomenon seems counterintuitive.

This behavior can be so perplexing, causing curls to disappear with a haircut or to suddenly begin developing as someone grows their hair out for perhaps the first time. While this seeming contradiction may be baffling and even frustrating, it is possible to understand what is going on if one looks at what causes hair to curl and some mathematic principles that can be used to describe curly hair.

Morphology of Hair

Human hair is a marvelously complex biomaterial, comprised of many nanoscale substructures woven together into intricate patterns, both beautiful and functional. The building block of hair is the protein keratin, which is made up of long chains of amino acids. The amino acids in the keratin strands have very specific bond geometries that give the fiber an α-helical conformation. Individual keratin fibers bundle together with other keratin fibers to form aggregates called microfibrils. Clusters of microfibrils bundle together into macrofibrillar structures which occupy the central cortex of the hair. Fatty acids and keratin-based cuticles encapsulate the entire strand.

Human hair keratin is made up of 14 percent sulfur-containing amino acids (cysteine and cystine”>. It is from these amino acids that many of the properties of hair are developed, particularly curl. When two strands of keratin are adjacent to one another, the –SH bonds for nearby cystine groups can be oxidized to form a disulfide (S-S”> bond between the two strands. This is a chemical crosslink that ties the adjacent keratin strands together. A high proportion of disulfide bonds twist the hair strand into a helical pattern. Adjacent hair strands tend to assume the same pattern, and then cluster together into multi-helical structures that form curls. In this manner, the nanoscopic structure is repeated at the macroscopic level. Nature loves patterns.

The permanent wave process exploits this by breaking disulfide bonds and then reforming them (and forming new ones”> with hair locked into the desired helical shape.  

There are a number of factors that contribute to degree of curliness.  These include, but are not limited to:

1. Shape of the hair follicle – Teardrop-shaped, cylindrical and oval follicles all produce hair with differing degrees of curl.
2. Angle of emergence of hair from scalp – Super curly hair has been found to emerge from the scalp at a different angle than straight hair.
3. Cross-sectional geometry of hair strand – Completely cylindrical hair strands are straight, while oval strands have more wavy characteristics. Flat, ribbon-like strands result in extremely kinky curly hair.
4. Quantity of disulfide bonds – A higher concentration of disulfide bonds results in a more pronounced helical pattern.
5. Prevalent morphology of cortex cells – The aggregation pattern of the macrofibrillar structures in the cortex affects the degree of curliness.
6. Presence of other genes or proteins – Several different research groups are exploring the presence of a protein that seems responsible for curl formation.

Helical Structures

We have established that the helix structure repeats throughout the hair from its most basic molecular building blocks into the bulk hair pattern. But what exactly is a helix? You may recall the spiral staircase geometry of the DNA-double helix strand from high school biology. A helix is a ribbon-like coil that occupies three-dimensions and is governed by specific trigonometric equations used to describe the length of revolutions and the pitch angle.

X (t”> = r cos t

Y(t”> = r sin t

Z = ct

Where t = [0,2π], c = constant, r = radius, and 2πc = vertical separation of the loops.

This three-dimensional mathematics can become a bit tricky to visualize, so it can be easier to eliminate the third dimension (z”> and think in terms of two-dimensional sine waves. Sine waves can be used to model many different types of oscillating cycles that occur throughout nature, such as sound waves, visible light waves, and radio waves. In trigonometry, we call the length of time or distance it takes to complete one full cycle the period.

If one were to examine a spiral hair curl, it would be possible to see that one full curl revolution would be equal to one complete cycle or sine wave. The distance required to complete one full cycle varies for everyone. Very kinky curly hair would complete more revolutions per the same distance than hair that is less curly. Think of it as higher frequency curl pattern.

Take an example of three different people, with three different degrees of curl, all having hair nine inches in length.

Person A: Her hair completes one full spiral in one inch. In nine inches, it complete nine full revolutions and appears to very kinky curly. If she were to grow it out longer, the weight would eventually stretch the curls out a bit, so that her curl pattern would relax. She would be said to have Type 4 hair.

Person B: Her hair completes one one full spiral every three inches. In nine inches, her hair completes three full revolutions and appears to be mildly curly. If she were to cut it short, it would appear wavy or even straight, but grown longer, it would develop into well-defined spiral curls. She would probably be said to have Botticelli or Type 3 hair.

Person C: Her hair completes one full revolution in six inches. In nine inches of length, her hair only completes one-and-a-half revolutions and appears merely wavy. If she were to trim her hair to be six inches or less in length, it would appear straight. If she were to allow it to grow out to be very long (eighteen inches or more”>, she would begin to see a pronounced curl pattern emerge. She might be said to have Type 2 or Type 3 hair, or even straight hair, depending upon its length.

Final Thoughts

Human hair is such an intricate structure, and it varies so much from person to person. The helical structure present in our very DNA makes itself apparent on a nano-level in the keratin strands that make up the foundation of our hair and is repeated at higher and higher levels until it is expressed in the gorgeous spiraling curls of our “kinky-haired” sisters and brothers.

Most of us with curly hair find ourselves with a mixture of all sorts of curl types on our heads, and we spend a lot of time and effort attempting to enhance, define and control them. Those with hair that takes longer lengths to really develop and show the curl patterns would do well to keep that in mind when cutting out hair. Lack of caution can lead to a disappearance of those precious curls. Remember the mathematics.

In order to get the best results in your curl pattern, you can figure out what your length for one revolution is and keep it in mind when growing or cutting your hair.

By Tonya McKay · Published November 2, 2011

Xanthan gum is found in many products, including food items, cosmetics and personal care products. It also appears in many shampoos, conditioners and styling agents. Its current popularity can in part be attributed to its plant-based origins and biodegradability. Home-based kitchen chemists who formulate their own products have found it to be a useful and easy-to-use additive for hair gels and conditioners.

What exactly is this material, though? Its name does not reveal much information regarding its chemical nature or its purpose in a product.

Xanthan Gum’s Chemical Structure

Xanthan gum is a naturally derived polymeric carbohydrate (polysaccharide”> with a very high molecular weight (in the millions of grams per mole”>. It is obtained via a fermentation process utilizing the bacterium Xanthomonas campestris, which can be obtained from a variety of plant-based sources.

The polymer backbone is comprised of repeating units of a simple sugar molecule (beta – (1,4″> D-glucose”>, and the side chains pendant to the backbone are trisaccharides, made up of alpha-D-mannose, beta-D-glucoronic acid, and beta-D-mannose paired with a pyruvate group. The side chains possess an anionic (negative”> charge, and they make up the bulk of the weight of the polymer, and thus contribute the majority of the properties for which Xanthan gum is prized.

Xanthan Gum’s Physical Properties

Xanthan gum is readily soluble in either hot or cold water. It is generally unaffected by pH, is very tolerant of electrolytes, and is stable over a wide range of temperatures. These properties make it extremely easy to work with both in formulation and production.

Xanthan gum is most often used for its unique rheological (affecting the flow of the liquid”> properties. In both neutral and charged solutions, it imparts higher viscosity to the formula, making it thicker and more resistant to flow. In a neutral solution, the polymer molecules are in the random coil state, and thickening is achieved primarily via chain entanglements between the very long polymers. Imagine a mass of spaghetti noodles all piled together in a bowl and how they all become intertwined with one another.

In solutions containing electrolytes, the polymer molecules collapse and form somewhat rigid helical rods that can pack together and form gel networks via hydrogen bonding. Polymers that form gels when mixed with water like this are called hydrocolloids. These gels are stable over a wide range of temperatures. Also, since the polymers are completely soluble in the aqueous solution, the subsequent gels formed are very clear, which is a highly desirable property in the styling product market.

Hydrocolloid gels made with xanthan gum are pseudoplastic materials, meaning that the viscosity of these solutions undergoes shear thinning (decreases”> when a shear force is applied. This makes it easier for the fluid to move or flow when it is shaken, stirred, or squeezed. What happens is that the forces break down the gel network so that the individual polymer molecules can slide past one another.

This is a great advantage both for processing the materials as well as for application as a finished good. Shear thinning reduces the effort required to squeeze or pump gel or lotion out of a bottle or toothpaste from a tube, which renders it easily applied to hair, skin, or a toothbrush. Once the shear force is removed, the gel network re-forms and the viscosity builds up again. This makes xanthan gum an excellent emulsion stabilizer also.

What Xanthan Gum Adds to Curly Hair Products

Xanthan gum is useful in shampoos, hair conditioners and styling products. It is a fantastic viscosity modifier, producing thick and creamy products that are very thermally stable. Its shear thinning properties also make it easy for the consumer to use. It is stable over a broad range of temperatures, is water-soluble and is a great binder of water.

It is also an excellent emulsion stabilization agent, which facilitates incorporation and prevents phase-separation of oil-based additives. It is compatible with anionic, cationic, and nonionic polymers.

The application in which xanthan gum’s properties really shine is in the styling gel. Xanthan gum dissolves completely, and so the gel formed is sparkling clear, which is a property highly desired by consumers. It is highly compatible with typical styling polymers, such as the cationic polyquaternium family, as well as the acrylates. It has been found to enhance the performance when used in products with these polymers, decreasing the amount of expensive synthetic polymer needed for a good result.

One producer of the polymer, National Starch, found that the polymer has extraordinarily good properties all by itself in water, as a hair fixative material. A simple formula containing water, xanthan gum (1 to 3%, by weight”>, and appropriate preservatives was found to provide a product with excellent rigidity of style, high gloss, insignificant flaking, good feel, and to have curl retention in high humidity that exceeded many traditional commercial products. What this means is that a styling gel containing xanthan gum will provide a curly style with excellent hold with no white, flakey mess, and that the style will stand up to heat, humidity, and time.

What an awesome material for the curly girl who desires to make her own products!

Make Your Own Xantham Gum Gel!

1. First add the preservative to water and mix thoroughly.
2. Add in the xanthan gum slowly, with lots of stirring or agitation, into cold or heated deionized water until the solution is clear and begins to thicken.
3. Pour into containers and set aside to allow gel network to form.
4. Experimentation with the addition of essential oils, other polymers, small quantities of salt (if you want a thicker gel”>, or plant oils can help personalize this product to your own tastes.

Final Thoughts

Overall, xanthan gum seems to be a win-win material. It is water soluble, which allows curlies all around to sigh in relief. It gives products that luxuriously thick texture and feel, stabilizes formulations so that all the ingredients can work as intended, and it adds excellent hold to styling products such as gels and mousses. In addition, the ease with which it can be used to create a product at home makes it a very attractive ingredient indeed.

The single caveat for potential consumers to be aware of is that it can sometimes be an allergenic material, as it is typically derived from wheat, corn, or soy. Fortunately, it is possible to obtain xanthan gum from the source of your preference. For instance, Bob’s Red Mill makes a certified organic food grade xanthan gum derived from non-GMO corn and soy products.

By Tonya McKay · Published October 7, 2011

Recently, there have been a number of articles and discussions comparing and contrasting silicate and silicone hair care products. The similar sounding names have led to some understandable confusion regarding the nature and purpose of these ingredients in shampoos and conditioners. Both are common ingredients found in a variety of products such as skin cleansers, shampoos, creams, masques, and hair conditioners.

Many curly-haired consumers avoid silicones or attempt to minimize or restrict their use in their hair care routine. However, the use of silicate-containing products is occasionally advocated based on the premise that they are “natural alternatives” to synthetic silicones. Unfortunately, this information is not entirely accurate and stems from a misunderstanding of the chemical nature and structure of these two very different types of materials.

A closer examination of the chemical and physical properties of each category should be useful for anyone who is curious about the molecular nature of these ingredients and what function they perform when included in hair care products.

Silicones

The Bane of the Curly World

Silicone hair products have been discussed extensively on this website and others, so this will be a quick review rather than an exhaustive treatise. They are a diverse family of synthetic inorganic polymers based upon polydimethylsiloxane that can be prepared and modified in numerous ways in order to produce materials suitable for a wide range of applications.

Silicones used in hair care products are typically long, flexible molecules with a backbone comprised of thousands of repeat units of some variation of –(O-Si-O”>- linkages with differing organic (carbon-containing”> pendant groups attached to the central silicone atom. These are typically liquid at room temperature and are oily in their consistency. They are most often insoluble in water, but are sometimes modified with ethylene glycol groups or other atoms to render them water-soluble.

The physical properties of silicones cause them to adsorb onto the surface of hair and to spread out, forming a smooth film, which increases slip along and between hair strands and decreases combing forces. This renders them superior conditioner agents and detanglers. Additionally, they provide thermal protection, which reduces structural damage incurred from the use of heated styling tools. They have also been found to increase the longevity of color in dyed hair.

Silicone polymers have a high refractive index, which allows them to impart an extraordinary level of gloss to the hair, which gives the appearance of shiny, glamorous tresses. Clearly, despite their reputation in the curly community, silicone polymers provide many direct benefits to hair when used in shampoos, conditioners and styling products.

Common Silicones in Hair Products:

• Dimethicone
• Cyclomethicone
• Dimethiconol
• PEG-modified dimethicone
• Amodimethicone
• Various copolymers

Is it a silicone or not? What’s in a name? »

Looking for ‘cone free conditioners? »

Browse hundreds or products and reviews of sulfate-free shampoo! »

Silicates

Not a Silicone Replacement

Silicates used in hair and skin care products are inorganic minerals called clays, which are mined from the earth. Similar to silicones, these minerals are comprised of silicon and oxygen. However, the similarity ends there. Unlike silicones, these are not long chains of repeat units, but are rather small clusters of ionically-charged, crystalline platelets with various metal ions associated with them.

Silicates are extremely hygroscopic, meaning not only are they water soluble, but they will absorb large quantities of water. Due to this property, as well as their plate-like structure, these materials are used in shampoos and conditioners as viscosity modifiers (thickeners”>. They are also effective as exfoliating agents, humectants and slip agents. They act as emulsion stabilizers and help prevent flocculation of ingredients. They have been found to have some beneficial properties for hair because they can help remove impurities and improve the health of the scalp.

However, silicates do not provide significant conditioning, detangling, thermal or color protection, nor do they impart gloss to hair. Their primary benefit is to the physical properties (viscosity and shelf stability”> of the formula in which they are included. They are not typically part of a formula for the same reasons as silicones at all. They are not silicone substitutes.

Common Silicates in Hair Products:

• Aluminum magnesium trisilicate
• Zirconium silicate
• Calcium silicate
• Sodium Silicate
• Bentonite Clay, sodium or calcium bentonite
• Montmorillonite clay

Silicates: the facial for your scalp? »

Shampoo bars and silicates work hand in hand! »

Hop in on the CurlTalk Convo: Is silicate a silicone?»

The Bottom Line

• Both silicones and silicates have significant, yet extremely different benefits, when used in a formulation.
• A person who chooses to avoid silicone hair products due to concerns about build up on the hair need not avoid silicates.
• However, one should be aware that silicate clays do not act as substitutes for silicones, and excellent conditioning products need to still be used regularly.

By Tonya McKay · Published September 2, 2011

Accumulation of mineral scale on surfaces due to hard water build up is an unfortunately common and truly aggravating problem. Most people have experienced the joys of living with hard water: cloudy, spotty dishes coming out of the dishwasher, diminished performance of coffeemakers, clogged or broken pipes and washing machines with an unpleasant odor that don’t work properly, turning clothes and towels dingy grey or a rust-tinged color.

Hair is susceptible to this menace as well, becoming dull, limp, or frizzy and more prone to tangles and hair breakage due to accumulation of minerals causing hair build up. Certain strong shampoos, such as clarifying or chelating ones, are marketed as solutions to some of this, but are there any options for those avoiding sulfate-based surfactants? As always, the answer to that question lies in the chemistry and materials science of the system.

Why Hard Water Creates Hair Build Up

If you have hard water, removing hair build up should be part of your hair care routine.

Hard water contains significant quantities of dissolved minerals, such as iron, calcium, magnesium, and silicon. These metals can react with substances in soaps and shampoos and reduce the effectiveness of those products’ cleansing properties, making it necessary to use more of the cleanser. But, even more disturbing, is that fact that the reaction products precipitate out of the solution and deposit onto the surface of your hair, where they bind with the negatively charged surface. This is what is typically referred to as mineral scale, which conjures up a bit of a mental image, if one considers it. Picture hard fish scales covering your hair, creating a rough surface that prevents moisture from penetrating the hair shaft, and you won’t be too far removed from the reality.

These deposits also attract and trap organic matter such as grease and dirt. This leads to hair that becomes increasingly difficult to deal with. It becomes dull instead of glossy, loses curl retention capability, is more prone to formation of snarls and tangles and is more easily damaged. It can even lead to the development of an unpleasant odor to the hair, particularly in dreadlocks.

Clearly, this kind of hair build up is not a trivial issue and should be addressed as a normal part of a person’s hair care routine.

How to Prevent Hair Build Up

The absolute best method for dealing with hard water is to prevent hair build up in the first place. One can do this by utilizing a good water filter that removes the unwanted metal ions from the water. Another technique is to use a chelating shampoo regularly, which has molecules in it such as EDTA, or acetic or citric acid. These acids bind with the metals in the water as you are washing your hair and are then rinsed away instead of depositing onto the surface of your hair. These shampoos can be harsh, though, and should always be followed up with a good conditioner, but even then, they may be damaging to curly hair if used too often.

Clarifying Shampoo Recommendations

• Elucence Volume Clarifying Shampoo
• Carol’s Daughter Rosemary Mint Clarifying Sulfate-Free Shampoo
• Hair Rules Aloe Grapefruit Purifying Shampoo

Vinegar rinses can possibly help loosen mineral scale so it can be rinsed, and it definitely helps dissolve some of the trapped organic matter that can be lurking in the residue. Clarifying shampoos can also help remove hair build up. It is not clear whether they actually remove mineral scale from hair, but they definitely can provide deep cleaning of any other matter adhering to the surface because of the mineral scale.

Chelating shampoos may be able to dissolve the mineral scale and help remove it from the hair. The Beauty Brains, a site run by cosmetic chemist/consultant Perry Romanowski, states their skepticism as to whether this works at all, which makes me yearn, yet again, for a lab with some really expensive equipment so I could run some studies, both to satisfy my own curiosity and so I could also give you all a definitive answer.

Gentle shampoos with surfactants designed to provide mild cleansing are undoubtedly capable of removing organic material and hair build up. This includes surfactants such as sodium cocoyl isethionate and coco betaine. However, it seems unlikely that these would have the ability to remove mineral scale by themselves. Fortunately, there are definitely some shampoos that contain mild surfactants, no added conditioning agents, and acids that are thought to aid in removal of hard water hair build up.

Final Thoughts

Since it is so evident that curly hair performs absolutely at its best when it has both a clean surface and a well-moisturized cortex, it seems imperative that you take some sort of measure to prevent or remove hair build up caused by hard water. The installation of a water softener or filter seems to be the best and most proactive solution. However, there are other alternatives, such as rinsing with vinegar and using chelating shampoos. It is of utmost importance that an excellent conditioner be used whenever one uses strong products like this on the hair, so don’t skimp on that step.

By Tonya McKay · Published August 4, 2011

The science of hair care has been a lively area of research and development for the past 50 years or more. Tremendous strides were made in the past two decades alone, thanks to advances in polymer and colloid chemistry. These advances were found in both the area of designing and producing extremely complex polymeric molecules and also in the area of understanding the mechanisms by which these molecules provide benefit. The incorporation of highly sophisticated polymers and polymer combinations into formulations has yielded curly hair products capable of truly protecting and enhancing hair, and efforts to optimize existing polymers and to synthesize new types are ongoing.

Silicones

Many currently available moisturizing curly hair products rely heavily upon the use of cationic polymers and silicone-based polymers as conditioning agents. Silicone polymers provide excellent smoothing of the cuticle, impart shine, protect hair from thermal damage, increase longevity of hair color and yield positive tactile feel to hair. Cationic polymers can work together with silicones to enhance their performance in conditioning shampoos. They can also work alone to provide excellent conditioning benefits, including superior combing force reduction.

However, these ingredients and the products that contain them have recently waned in popularity with consumers, primarily due to concerns about buildup of those substances on hair. This trend has not gone unnoticed in an extremely market-responsive industry, and has, in fact, been a huge driving force behind research and development efforts. These projects have been ongoing, both at raw materials suppliers and finished good manufacturers, with the objective to develop and produce replacement polymers and silicone-free formulas.

One such project recently came to fruition when Dow Personal Care, a subsidiary of Dow Chemical, released its new conditioning platform, EcoSmooth Polymer Technologies.

Their product literature states that the platform is comprised of two types of polymers: EcoSmooth Silk and EcoSmooth Satin, which they claim will “reinvent conditioning.” An examination of these polymers and how they compare to more commonly utilized polymeric conditioning agents may provide curlies with insight to help them decide whether or not to give these materials a try.

EcoSmooth Silk

EcoSmooth Silk is a polyolefin water insoluble copolymer emulsified using a proprietary acrylic-based polymer dispersant with the INCI name: ethylene/octene copolymer and ethylene/sodium acrylate copolymer. This polymer is marketed as a replacement for silicone.

Marketing and technical literature published by Dow Personal Care describes EcoSmooth Silk as “a non-cationic technology that matches silicone in wet and dry combing and minimizes hair breakage.”

Although this polymer is a hydrophobic one (i.e. not water soluble”>, Dow reports that they did not observe evidence of appreciable buildup after repeated use. The method they used to make this assertion was based upon volume of the hair after repeat application. With silicones, which do build up over time, hair volume is found to diminish. Hair treated with the EcoSmooth polymer was found to have greater volume after multiple applications than that treated with silicones.

No actual chemical analysis or surface analysis of the hair was reported or described to substantiate this claim, although it may exist. This polymer should be removable using a mild shampoo, but shampoo-free users may wish to proceed with caution.

EcoSmooth Satin

EcoSmooth Satin is a non-cationic conditioning polymer with the INCI name: Ethylene/Sodium Acrylate Copolymer. It can be used to replace cationic polymers such as polyquaternium-7 and guar.

Dow claims that it provides equivalent sensory and foaming performance to those two polymers and that it provides superior performance on damaged European hair in particular. This means that the tactile feel is better to the consumer both during and after use.

When compared to cationic guar applied to damaged hair, EcoSmooth Satin was found to demonstrate a superior ability to reduce wet combing forces, making it easier to detangle hair and to significantly reduce the percent breakage of hair.

Satin is a water-soluble anionic polymer in solution that deposits onto the surface of the hair via a dilution deposition mechanism, where it binds to hair via hydrophobic interactions. Cationic polymers bind electrostatically to the surface of negatively charged hair via a charge-charge interaction. So, while both types of polymers are water soluble, Satin should be more easily removed from the surface of hair due to weaker interactions between the hair and the polymer.

For this reason, it seems reasonable to expect a buildup free experience when using curly hair products containing this polymer, presuming other ingredients in the formula are not prone to build up themselves.

Wrap-up

It is truly exciting to observe the sophisticated application of polymer science to the development and optimization of hair conditioning products. Silicones and cationic polymers have provided formulators with seemingly endless formulas that have truly stellar performance on hair.

Yet, there are many more possibilities, as Dow has clearly demonstrated with the launch of EcoSmooth Polymer Technologies. These polymers appear to be promising as conditioners used in curly hair products, as they seem to be less prone to buildup and also have demonstrated an ability to reduce breakage.

It will be interesting to see how these materials work in commercially available products, and also to see what other polymers will emerge onto the scene in the future.

By Tonya McKay · Updated May 28, 2024

Illustration of oil droplets suspended in water (emulsion”>

Illustration of a micelle

Depiction of a sterically stabilized emulsion

Recently, an insightful reader asked whether a certain styling product advertised as “water-soluble” could possibly be so. The specific reason for the inquiry was the presence of petrolatum and mineral oil near the top of the ingredients list. Of course, my reflexive response to this question is “no.” Petrolatum and mineral oil are both decidedly hydrophobic materials, and they are not, nor will they ever be, water-soluble. However, this product is definitely described in the marketing material as being water-soluble, so it seemed worthwhile to give this a closer look and see what answers may be found in the chemistry of the formulation.

The product in question is Curlisto’s Unruly Paste, recommended for use on dry hair to provide curl definition, shine, and to tame frizz. It is described on their website as being non-sticky, non-oily, and “water-soluble.”

It is possible to glean a good bit of useful information about Unruly Paste by analyzing the ingredients list. Unlike many similar types of products, this is a water-based styling crème. It contains humectants (propylene glycol”>, a water soluble fixative polymer (VP/VA copolymer”>, a significant percentage of higher molecular weight oils/waxes (petrolatum, mineral oil, and ozokerite – a mineral wax mined from the earth”>, a non-water soluble silicone for shine and smoothing, and a large quantity of emulsifying agents.

Micelles are aggregates of surfactant molecules in water, comprised of an exterior shell of the hydrophilic portion of the surfactant and a hydrophobic center containing the non-polar segment of the surfactant. In this product, the surfactants form micelles that contain the mineral oil, petrolatum, and/or ozokerite in their core.

The nonionic emulsifying agents prevent coagulation and phase separation of the waxes by a mechanism known as steric stabilization. This is where the hydrophilic portions of the surfactant molecule extend out into the aqueous solution and form a bit of a tangle around the micellar aggregate. This tangle physically prevents micelles from coming together and joining to form bigger micelles, a phenomenon that would eventually destabilize the system and result in phase separation.

Technically, the non-polar waxes are solubilized or dispersed into the water using these emulsifying agents and are water soluble while in these aggregate forms. To reiterate, they are only soluble by nature of their containment within the interior of the micelles formed by the surfactants. (You may recall that we have had similar discussions about amodimethicone, as used in certain shampoos and conditioners.”> These types of mixtures are called emulsions, because they are not solutions by proper definition.

Once the product is applied to the hair, the micellar structures are disrupted, the waxes are deposited onto the surface of the hair, and the water from the product evaporates into the air. Since this is a leave-in product, the surfactants remain on the surface of the hair even after the water evaporates, but they no longer serve much purpose except to perhaps attract water molecules to the hair from the environment.

The question is when hair that has been treated with this crème is immersed in water, will the emulsifying agents somehow re-form the micellar structures and re-absorb the waxes into their cores, allowing them to be rinsed away? It is my opinion that this scenario is highly unlikely, as the original process of preparing the product relies heavily upon proper order of addition of ingredients, judicious mixing and agitation, as well as the application of heat in order to form these types of structures in the first place.

However, it is possible that if one were to use a very mild shampoo or even a light conditioning product and gently agitated the hair, that the residual emulsifying agents on the hair might be able to aid in removal of the waxes from the surface of the hair. Generally, one would need to use quite potent shampoos to remove petrolatum and mineral oil from hair, and it would probably be necessary to rinse and repeat.

Final thoughts

Thus, it would seem possible that this method could alleviate some of the accumulation that inevitably occurs from use of typical products that rely upon these types of waxy ingredients. “Water-soluble,” though, seems to be a bit of a marketing stretch.

By Tonya McKay · Updated May 28, 2024

One of the primary indicators of the health of your hair is its elasticity. Healthy hair has a high level of elasticity, which gives it body, bounce and curl formation. Elasticity makes it possible to style hair and also is responsible for curl retention. But what exactly does the term elasticity mean? We know it has to do with the stretchiness of our hair, and we know it is a desirable property, but it may not be entirely clear what it is.

Also, what contributes to elasticity of hair, and how can we maintain or improve the quality in our own locks? These are important questions, and as always, much insight can be gleaned by an examination of the fundamental principles as well as the molecular structures that make up the hair.

What Does Elasticity Mean?

Elasticity is a term used to describe how a material responds to the application and removal of a specific type of mechanical load (pulling and/or bending”>. When a stress (force per unit area”> is applied to a material, it stretches a certain amount beyond its original length. This deformation is dependent upon the stiffness or rigidity of the material. The ratio of applied stress to the amount of deformation/elongation that occurs is called the elastic (or Young’s”> modulus.

Rigid materials, such as iron, stretch very little with an applied force, while other materials, such as synthetic rubber, can stretch many times their original length without breaking. Dry hair can stretch to approximately 1.2 – 1.3 times its original length and still return to its dimensions, while wet hair is less rigid than dry hair and can stretch up to 1.5 times its length. Curly hair can stretch even more than straight hair can, as it is highly coiled in its relaxed state.

A material is said to exhibit elastic behavior if it returns to its previous shape and size once an applied force is removed. This is called reversible deformation. Simple materials such as elemental metals typically display purely elastic behavior. These tend to stretch to a certain point and then experience sudden fracture if the stress is not removed. Materials such as these are described as being brittle.

More complicated materials such as polymers, proteins, biomaterials and some inorganic amorphous solids exhibit elastic behavior until a certain stress is exceeded (yield strength”>. Beyond this point, less force is required to induce further deformation, and the material is unable to recover its size and shape once the load is removed. This phenomenon is referred to as irreversible deformation, plastic deformation, or permanent set. The applied force causes something to change inside the substance at a molecular level that causes it to become fundamentally different in its physical structure. The change can be a rearrangement of crystalline lattice structure from one type to another, shifting or slippage of molecular alignment in an amorphous or semi-crystalline material, change of protein tertiary structure, or breaking of bonds in polymeric compounds. Materials with this property are referred to as being ductile or having greater toughness than brittle substances.

Plastic deformation is particularly relevant to the health hair and its appearance. If excessive force is used to style or comb hair, the yield strength can easily be exceeded, and the hair can no longer bounce back when it is pulled out of shape. This can adversely affect its ability to hold a style or retain curl and can result in shapeless, frizzy hair.

Additionally, special caution should be taken with wet hair. Hair saturated with water is fragile and can stretch much more easily than when it is dry. It is very easy to exceed the yield strength when hair is wet and permanently diminish its elasticity, or even cause breakage. For this reason, it is crucial to use extreme care when handling and combing wet hair. The use of a good conditioner helps protect wet hair from plastic deformation by decreasing combing forces (less force is required to get the comb through tangles”>.

What Affects Hair Elasticity?

The interior of the hair shaft, the cortex, is the portion of the hair structure that carries the bulk of an applied load and contributes most significantly to elasticity. Although it is very important, the cuticle is only significant in this regard for its role in guarding the integrity of the inner shaft of the hair.

The cortex is an elaborate structure of clusters of fibrils of keratin protein embedded within a matrix with high water content. The individual molecules of keratin are in the alpha-helical conformation. There are many different inter- and intramolecular interactions and bonds that occur both between amino acids on the same protein strand, amino acids on adjacent protein chains, and between proteins and water molecules within the matrix.

Hydrogen bonds are weak physical bonds that occur between aqueous hydrogen and amino acid nitrogen and oxygen atoms. These interactions are easily formed and broken and are responsible for a large portion of the elastic behavior of hair. For this reason, it is very important to maintain a proper amount of moisture inside the hair shaft. Without adequate hydration, hydrogen bonding will be decreased, which adversely affects elasticity of hair strands.

Salt bonds are weak physical interactions that occur between amino acids and require hair to be maintained at an optimum pH. Cystine bonds, also known as disulfide bonds, are chemical bonds which impart a high degree of elasticity to hair by providing crosslinks between different amino acids on a single protein fiber and also between protein strands. All of these various types of bonds act to hold strands of protein together and allow them to stretch just so far and to snap back into their original shape.

Another factor that influences the elasticity of hair is its diameter. Hair of smaller diameter cannot withstand the same forces as hair of thicker diameter. Remember, stress = force per unit area, so thinner hair experiences greater stresses at the same forces. This means that those with finer hair may have more trouble with their hair losing curl, not holding styles, and developing frizz and breakage. African hair typically has the smallest diameter, with Caucasian hair having medium diameter, and Asian hair having the thickest diameter. There is no known way to overcome this, so one must take care to treat fine hair with the same care one would afford your most precious cashmere sweater.

How to Improve Hair Elasticity

We have learned that hair elasticity is heavily dependent upon two key factors: 1.”> hydrogen bonding between water molecules and keratin strands and 2″>. disulfide bonds between adjacent cystine amino acid groups, both of which are dependent upon preservation of the protein structure and hydration of the cortex. The best approach to ensure excellent elasticity is to maintain an intact protein structure inside the cortex and an adequate level of hydration.

In an ideal world, prevention of damage to the cortex protein structure is achieved by maintaining a pristine cuticle layer, avoiding high temperature treatments and processes, avoiding chemical processes such as color, permanent waves and relaxers, minimizing UV exposure, limiting hygral fatigue (excessive water exposure”>, and using only the most gentle mechanical forces for combing and styling. Of course, we don’t live in an ideal world, so most people will experience varying levels of degradation of the internal protein structure of their hair, accompanied by a gradual deterioration of the desirable elastic properties. Minimizing exposure to destructive processes and frequent trims helps defray damage, as does use of a good deep conditioner and gentle treatment of hair at all times.

The use of protein treatments and protein-containing conditioners is often recommended to help improve or restore elasticity. This approach can be useful for those who do have damaged proteins in the cuticle structure or within the hair shaft. Hydrolyzed proteins in these products are in amino-acid form and lower molecular weight poly-peptide form, and can penetrate the cortex. They are retained there in subsequent washings and can contribute to hair strength and integrity to some extent, preserving the tendency for elastic, reversible deformations at low stresses. However, it is most likely that these materials act only as a patch over a hole rather than actually assimilating themselves into the protein strand and fibrillar structure. One word of caution about these types of treatments is that they can potentially contribute to brittle behavior (breakage”> if used in excess or if the hair already has sufficient protein content.

For a substance that seems mostly decorative, hair never ceases to amaze me in its complexity. The intricacies of this biopolymeric composite are simply amazing. The elastic properties of healthy hair can serve us well and allow for much versatility in our coiffure, if proper care is taken to keep hair in the best shape possible.

By Tonya McKay · Published May 4, 2011

In the cosmetics and hair care industry, a continual stream of new products are introduced into the market. Most seem to be variations of whatever happens to be the current popular theme. On occasion though, new products emerge onto the scene bearing remarkable claims that demand closer examination.

One such recent case is the Nexxus Pro-Mend system, which the manufacturers assert can nourish hair and actually heal split ends. Who wouldn’t be intrigued by promises that the product could repair up to 92% of split ends in the first use? It seemed a sufficiently brazen claim to warrant some scientific detective work to determine if the claims are credible, and if so, what the chemical basis is for the reported miracle cure for split ends.

Too Good to Be True?

The initial response many may have when hearing such a claim is that it is preposterous. We have all been taught that hair is a “dead” protein, and that topical treatments such as hair products are incapable of providing anything other than cosmetic, superficial, and temporary benefit. However, our understanding of and facility with protein and polymer chemistry has been continually advancing in unexpected and oftentimes brilliant ways. For this reason, I am willing to temporarily set aside my skepticism and entertain the notion that maybe someone has finally found a way to repair split ends without a pair of scissors.

There is a general procedure one can follow to gain fundamental insight into the technology behind a new product. The first step to understanding is to examine the ingredient list and look for anything new or unusual combinations of materials. Next, it is helpful to review the company’s marketing material and instructions for use of the product. Finally, one can gain a tremendous amount of valuable information by scouring the relevant technical literature and patents (even those of competitors or for products used for completely different applications”>.

Analysis of the Ingredients

Nexxus Pro-Mend Leave-In Treatment Cr̀eme Ingredients

Water, Phenyltrimethicone, Dimethicone, Stearamidopropyl Dimethylamine, Polyquaternium 37, Polyquaternium 28, Cetyl Alcohol, Glycerin, Cyclopentasiloxane, Aspartic Acid, Propylene Glycol, Dicaprylate/Dicaprate, Fragrance (Parfum”>, PPG 1 Trideceth 6, Glyceryl Stearate, PVM/MA Copolymer, Dimethiconol, DMDM Hydantoin, Disodium EDTA, Sodium Hydroxide, Hexylcinnamal, Butylphenyl Methylpropional, Limonene, Coumarin, Linalool, Alpha Isomethyl Ionone, Cocos Nucifera Oil (Coconut”>, Keratin Amino Acid,Jasminum Officinale Flower Extract (Jasmine”>

I was slightly taken aback by the ingredients for the products in the Pro-Mend line, which were not exactly what I expected to see in a novel intense conditioning formula. The major components listed are silicones and polyquaternium conditioning agents. The use of cationic polymers (polyquaterniums”> is not surprising, as they are selectively attracted to damaged areas of hair (which bear a negative charge”>. For this reason, they can be particularly useful in smoothing damaged cuticles and managing split ends. However, this is not a novel application of these materials. At first glance, nothing else jumped out as a likely character that would be able to repair split ends.

The first eight ingredients after water are found in many conditioning products, so no surprises there. After that are oils, emulsifiers, humectants, solvents, one fixative, and other common conditioning agents. But again, none of these ingredients are really known for doing anything terribly novel in terms of hair repair. Most are topical film-formers possessing varying ability to smooth, condition and protect the surface of the hair.

So, was that it? Was Pro-Mend merely another iteration in the long line of conditioning products available? Perhaps not. After further contemplation of the formula, I began to think there was more to these products than first meets the eye.

Several ingredients stood out in the list and nagged at my subconscious. Among these were Aspartic Acid, DMDM Hydantoin, Sodium Hydroxide, Hexylcinnamal, Butylphenyl Methylpropional, and Keratin Amino Acids. These ingredients are not uncommon and each has its own typical and often mundane purpose in a product. However, some of these are capable of performing double duty, and the presence of all of these ingredients together led me to have some suspicions as to how this product could possibly do the things they promised it could do. But, I needed more information.

The Marketing Story

The marketing materials for these products were the next step in the investigation. Nexxus says that after one use of the system (shampoo, conditioner, leave-in creme, and heat protection spray”>, 92% of your split ends would be repaired. This is such an exact number, which can be quite convincing when used in advertising, but I could find no data published anywhere to support this. There was no description of how they defined, ascertained, or quantified repair, but they did show a nifty video of a damaged hair strand coming back together. Their marketing materials use words such as “binding” and “healing” and “nourishing” to describe the effects of their products on damaged hair.

The thing that most interested me was a brief video in which they provide instructions for the proper use of the product. After shampooing, conditioning, applying leave-in cream, and using the thermal protector spray, the consumer is directed to blow dry her hair using a round brush and to follow up with a flat iron. The celebrity stylist assures us that the repair and strengthening results will be instantaneous and will last two to three months or longer with continued use of the product.

Ding, ding, ding! With this last piece of information, my glimmer of suspicion transformed into a raging hypothesis. (Is there such a thing as a raging hypothesis? How about a really excited, bouncing up and down hypothesis? I know, I am a science nerd.”>

The Proposed Mechanism

The combination of several aldehydes (hexylcinnamal, butylphenyl methylpropional”>, a formaldehyde-donor preservative (DMDM hydantoin”>, a drop of base (NaOH”>, a few keratin amino acids, and a recommendation to use high heat (flat iron”> all indicate to me that this hair system could be exploiting the same chemical mechanism used in the Brazilian keratin straightening treatments. (reference this previous piece for more detailed chemical information about Brazilian Keratin Treatments”> The general idea is that aldehydes react with amino acid side chains of hair keratin and also with the hydrolyzed keratin amino acids in the product. This enables them to effectively form bridges between the split pieces of hair and to bond new keratin onto the surface of the hair. These bridges could “glue” the hair strand back together and also give it a smoother, glossier appearance.

If this is indeed the mechanism being utilized, it is important to note that while the effect may be cosmetically pleasing and somewhat sturdy, the split ends of the hair are bound in a manner similar to a torn piece of paper that has been glued back together. It will hold and may look nice, but the weakness or flaw is still there. The crosslinked bridges that are formed by the aldehydes are not permanent and usually last two or three months.

Conclusion

The scientists at Alberto Culver (parent company to Nexxus”> have developed and cleverly marketed a very interesting new product that promises to repair and prevent split ends. Traditional moisturizing conditioners and protein treatments provide topical smoothing for hair and can fill in some gaps in the cuticle and hair shaft. However, none have been able to bind together pieces of a hair that has split into pieces. Analysis of the product ingredients leads me to believe that this product may in fact be binding the pieces of hair together via aldehyde reactions with keratin amino acids. If so, this is a very creative application of this technology.

Without direct confirmation from someone at Alberto Culver (soon to be Unilever”>, I am purely speculating about the chemical mechanism of the Pro-Mend products. I did consult the literature and patent space though, and happened across at least two patents that indicate that my hypothesis is plausible. It would be wonderful to learn the exact truth, but in this competitive market, it is best to keep one’s cards close to one’s chest.

The important things to note about this product are that it does seem to be an effective conditioning system, and many have reported an improvement in the appearance and strength of their hair. However, it does contain aldehydes and the makers do recommend using high heat on your hair for best results—something which many of us tend to avoid due to concerns of thermal damage. Finally, while the Pro-Mend system may chemically glue split ends back together temporarily, there is just no replacement for regular haircuts.

By Tonya McKay · Updated May 28, 2024

Gray hair has a higher susceptibility to damage when exposed to UVA and UVB radiation.

Those with a significant amount of gray hair are keenly aware that it behaves differently than the rest of their tresses. By definition, gray hair is lacking color, leading to less luster and shine. It often doesn’t have the same curl pattern or texture as the rest of the hair, which can make it appear unruly. Gray hair may also seem drier and more prone to frizz. However, really well-kept gray hair can be quite attractive. It is very delicate, though, and is especially prone to photo degradation and yellowing when exposed to excessive amounts of sunlight. This tendency is of particular concern as spring approaches, and many plan to spend more time outdoors gardening, swimming, or just basking in the sunshine. Fortunately, being armed with knowledge of the unique risks of sun exposure to gray hair can make it possible to prevent damage and maintain a healthy head of hair. So what does science tell us about gray hair and ultraviolet rays?

Testing and Data

Researchers have done comparative studies on various physical and chemical properties of blonde, brown, and gray hair, both before and after UV irradiation. One notable study examined a wide array of properties, including tensile modulus, tensile strength, wet combing forces, degree of swelling in basic solution, cuticle abrasion, and dynamic contact angle. They also assessed changes in hair color with exposure to UV radiation. All of these properties provided them with indirect information about the biopolymeric structure of the hair strands and how they were affected by the experimental conditions.

What they found was that the gray hair had a much higher susceptibility to damage than did the brown hair when exposed to both UVA and UVB radiation. The samples had a higher loss of mechanical strength, greater color change (yellowing”>, increased cuticle damage, and exhibited a marked transition from being hydrophobic to hydrophilic at the surface of the hair strands. This meant the gray hair was more likely to exhibit signs of yellowing after exposure, to become more easily tangled, to lose moisture easily, and to break. It was evident to this group that gray hair requires protection if it is going to be in the sun for prolonged periods.

For this reason, these researchers also performed their study using two different UV absorbers that have been used successfully in skin care products. One was octyl methoxy cinnamate (OMC”>, a commonly utilized sunscreen additive, frequently found in hair care products marketed as being effective for color retention and sun protection. The other ingredient was cinnamidopropyltrimonium chloride (CATC”>, a quaternized (cationic”> UV absorber. Each UV absorber was applied to the hair via a soak/rinse cycle in a simple shampoo-like solution of SLS/sunscreen. The samples were irradiated for specified periods of time and then run through all of the same testing as the ones previously discussed.

Protect your gray or graying hair from sun damage.

The results showed that each UV absorber offered some protection to the hair, as the deterioration in properties was lessened measurably. However, the traditionally used OMC offered substantially less benefit than CATC and really only demonstrated marginal improvement over no treatment at all. It was found that the cationic UV absorber (cinnamidopropyltrimonium chloride”> was more substantive to the surface of the hair after rinsing and was much more effective at maintaining the integrity of the hair for every single test. The molecule also had the property of being a mild conditioning agent, and added greater benefit to a formulation than the conventional OMC. CATC worked very well in oil-based leave-on sprays as well as shampoos, and the scientists concluded that it had real potential for helping prevent damage to gray hair (or any hair, for that matter”> from the sun.

One important caveat is that it is not really possible to quantify the efficacy of sunscreens used in hair care products in the same manner as for sunscreens intended for skin protection. No standardized methods or tests exist for evaluation of sun protection for hair, and even if there were, consumer variability in application would render much of that type of data useless. Many cosmetic chemists completely dismiss any value to including UV absorbers in a hair product, despite the heavy marketing campaigns insisting otherwise. While I often share their skepticism regarding unlikely claims by manufacturers, this particular study showed that there does seem to be some benefit to formulating with cinnamidopropyltrimonium chloride (at least for the conditions in this particular study”>.

Summary

Scientists have long been interested in how the physical properties of gray hair differ from those of pigmented hair. Unfortunately, for those of us with gray or graying hair, research has shown that it is more susceptible than pigmented hair to various types of damage from UV radiation. Happily though, there does seem to be at least one UV absorber (and certainly others not covered in this study”> that can help protect gray hair from damage in the sun. There are several products on the market that contain this ingredient, including Paul Mitchell’s Color Protect Daily Conditioner, Soma Hair Technology’s Colour Protect Shampoo and their Leave In spray, Kenra Platinum Smoothing Cream, and Aveda’s Color Conserve Shampoo, to name a few. Not all of these products are necessarily compatible with the shampoo free method, but some are. Just make sure to check the ingredients list to be certain the product is right for you and your personal preferences. Products like this work best at minimizing incidental daily damage, in my humble opinion, so grab a cute straw hat or a pretty scarf to cover your hair when you plan to be in the sun for an extended time.

By Tonya McKay · Published February 3, 2011

All hair gels are not created equally

Don’t be a flake!

It is not uncommon for various users of the same hair gel to report different performance results, sometimes drastically so. It can be very unnerving and discouraging to try a popular, highly recommended hair gel, only to discover that your own hair becomes completely unmanageable or develops a case of highly unattractive white, flaky mess. What can be even more frustrating is the fact that the same product that yielded perfect hair one day might produce really undesirable properties another day. It can be discouraging enough to make a person question their ability to properly use a product, or perhaps even begin to think their hair is just flawed or something. However, there typically is a good reason for this type of unreliability, and it can be found by examining the ingredient list.

So, what is the source of this variability, and how can an ingredient-savvy person select a product that will yield a predictable outcome? The answer lies in the chemistry and materials science of the ingredients, of course, most specifically the polymers.

You may need different gels for different seasons

Polymers

Polymers are the large molecules used in hair gels to provide the styling and hold properties. When the gel is applied to the hair, the product spreads out evenly over the surface of the strands and creates clumps of hair that are attracted to one another via capillary and Van der Waals forces. The product dries to form a clear, shiny film that acts to encapsulate and hold the hair in place and give it form and lasting hold (also known as curl formation and retention”>. A variety of naturally derived, synthetic and combination polymers are used to this effect, and all have their inherent strengths and weaknesses.

Most formulations are a balancing act between pros and cons of the ingredients. In order to improve one property, it is typical to lose ground in another property. For instance, it is desirable for a product to provide strong hold, yet for the film to be durable and not brittle. It is desirable for a gel to resist humidity from the environment, but also for it to be water soluble and easily removed from hair. However, these objectives are naturally in conflict with one another. Polymers can give special advantages to formulators in this respect, as it is possible to tailor one to meet multiple requirements. Cost is often a limiting factor, though, as the more fancy and specialized a polymer is, the more difficult it can be to obtain in sufficient quantities and at a reasonable price.

So, what specifically causes white flaking? Some polymers form really strong films with high tensile strength that also adhere very well to the hair. These molecules are not very flexible, though, and when enough force is applied to the hair (touching the hair, scrunching, styling, wind”>, they will essentially shatter like glass into many small particles. These particles lose their clarity and become unattractive white flakes on the hair and scalp. This tends to be more of a problem in cold, dry weather.

PVP is water-soluble, best used in moderate humidity zones

PVP (poly n-vinyl-2-pyrrolidone”>

A polymer that is notorious for having these issues is currently seeing an upsurge in usage amongst products targeted at curly-haired consumers, and that is PVP (poly n-vinyl-2-pyrrolidone”>. PVP is an excellent film-former, is relatively inexpensive, and most notably, is completely water soluble. The water solubility is extremely attractive to companies who wish to sell products to consumers who do not use shampoo or who use very mild shampoos, as it makes the gel easy to rinse. However, PVP can be very brittle and prone to flaking in cold dry weather. It also is hygroscopic and absorbs moisture from the air in humid climates, which can impart a tacky, sticky feel and lead to frizz and other unpleasantness. Clearly, a product which relies on PVP for its styling properties is likely to yield varying results depending upon local climate and individual handling of the hair once the film is dry. It seems prudent to perhaps avoid use of PVP-based gels, unless you live in a very moderate temperature and humidity zone (and you aren’t apt to handle your hair physically much once the gel is applied”>.

PVA (poly vinyl acetate”>

PVA (poly vinyl acetate”> overcomes some of the drawbacks of PVP. It is less apt to absorb moisture from the atmosphere, as it is water resistant. It is also a more flexible material, so it can bend without breakage, therefore, flaking is not an issue. However, it is not as substantive to hair as some of the other polymers (such as PVP or the polyquaterniums”>, and as a result curl retention or style hold is poor, and the effects wear off during the day.

Co-polymers are strong, yet tough and less likely to flake

Co-polymers

Co-polymers such as PVP/VA copolymer and acrylates copolymer are designed to bring more balance to a formula. These materials have segments that are rigid and water soluble, and also have segments that are water resistant and more flexible. This creates an overall polymer that is strong, yet tough and less likely to flake. The polymer is sufficiently water soluble as to be fairly easily removed from hair, yet it is hydrophobic enough to resist absorption of moisture from the local environment.

Other polymers can also offer various advantages, such as polyquaternium (cationic”> polymers, which can provide conditioning and smoothing properties, as well as good hold and humidity resistance. Polyurethanes are excellent for thermal resistance for heat styling.

Research is ongoing to find the perfect polymer or polymer system that can meet all of the requirements for a gel, but it is likely that we will always be settling for the “best fit” for the desired purpose. Besides, it would be boring (and potentially career-threatening”> if we always had to choose the same polymer every time. It is fun to play with different ones and with various combinations of polymers and other additives. The educated consumer can determine which product or products is best for their hair and their environment by closely examining the ingredients list and asking questions if they find ingredients about which they are unsure. You may need one product for summer and one for winter too, depending upon where you live.

By Tonya McKay · Published January 10, 2011

Scalpure

Recently, there has been some discussion in the curly haired community about products such as Scalpure, which marketed as a facial treatment for the scalp. The makers of such products maintain that that the products can provide a number of benefits to hair, such as stimulating hair growth, reducing excess oil production, and improving dandruff symptoms, among other things. These are rather bold claims, but perhaps are not without some scientific merit. The idea behind the development of this product is rooted (pardon the pun”> in the theory that the health of our hair begins with the health and wellbeing of the scalp and follicles. As the makers of Scalpure say, “the scalp is the soil for the hair.” Examination of the ingredients list should provide us with some scientific insight into whether or not the treatment can possibly live up to these promises.

Most of the ingredients in this list are fairly self-explanatory. Purified spring water is the bulk solvent for the product, so it is not an oil-based treatment, which makes it easier to rinse out of the hair. The various essential oils and plant extracts in the list are all familiar to most of us and are commonly found in many products.

These types of oils can soothe dry skin, plump and smooth hair, stimulate blood flow to the scalp, improve circulation and thereby enhance cell growth in follicles, act as anti-inflammatory agents, and provide antimicrobial and antifungal benefits. These oils also have a lovely aroma, which can provide the user with a sense of emotional energy and well-being.

To me the fascinating ingredient in Scalpure is calcium bentonite, which is a crystalline inorganic material that is a member of the smectite clay family. It is sometimes known as Montmorillonite clay. Its chemical structure is hydrated sodium calcium aluminum magnesium silicate hydroxide, shown empirically as: (Na,Ca”>0.33(Al,Mg”>2(Si4O10″>(OH”>2·nH2O

This aluminosilicate clay is mined from various sites around the world, refined, purified, and then used as raw material for many different applications.

The crystalline structure of calcium bentonite is much like a playing card. The silicon-aluminum-oxygen crystal forms an ionically charged platelet structure. Typical platelet edge thickness is around one nanometer, while the face can be as much as several hundred nanometers across. The broad, flat surface is covered with negative charges, while the edges are very slightly positively charged. This lends an overall negative charge to these crystals.

The total cumulative charge is directly proportional to the total surface area of the crystal. As particle size decreases, the overall surface area increases, and thus the particles become more highly negatively charged. This property makes these materials very interesting for nanotechnological research and applications.

Natural or chemical?

A positive metallic ion (usually either sodium or calcium and sometimes magnesium”> is associated with each crystalline face. These are known as exchangeable ions, as they vary according to the source of the mineral. The effect of these cations is to significantly reduce the overall negative charge of the platelets. Montmorillonite clay is quite hydrophilic and readily attracts and adsorbs water to itself. When hydrated, bentonite crystals aggregate together to form a three-dimensional structure known as a house of cards, with a layer of water between each card.

When the positive counterion is sodium, these clays retain a higher degree of negative charge and are thus extremely hygroscopic. In this form they swell tremendously due to absorption of large quantities of water molecules, which can be hazardous in biological applications. However, sodium bentonite can be very useful in many other applications, particularly in the mining and petroleum industries. Calcium bentonite is the preferred form for most cosmetic and pharmaceutical uses, as it still swells in aqueous systems, but it is not quite so hygroscopic as the sodium form.

The unique ionic, three-dimensional, sandwich-like structures of calcium bentonite impart extremely interesting and useful properties to these materials. They are excellent colloid dispersant agents and highly effective emulsifiers as they can trap oils in the layers between platelets. They also can enhance the structures of micelles in solution and aid in the development of liquid crystalline structures, such as vesicles.

Bentonite clays are often used as viscosity modifiers for fluid systems that require thickening but that are also expected to be easily spreadable or dispensable. Consider toothpaste. It must be sufficiently viscous to fill out and remain inside the tube, but it must also be easily squeezed and dispensed onto a toothbrush. Bentonite clays are pseudoplastic materials (those with non-Newtonian properties”> that exhibit this type of thixotropic behavior, which means that the viscosity of the system decreases over time with a constant applied shear force.

The properties of bentonite also make it very compatible with ingredients typically found in cosmetics and hair and skin care products, such as anionic and nonionic surfactants, oils, fats, salts, and waxes. They are highly effective at stabilizing oil-in-water emulsions, and for this reason make excellent emulsifying agents for many applications.

The smectite clay structure and ionic properties of bentonite are also useful for the removal of heavy metal toxins as well as certain pathogens that are positively-charged. These materials are adsorbed onto the negative surface of the platelets, and effectively carried away inside the “sandwich” when the product is rinsed or digested.

Oil extracts are often healthy for the hair

So, when examining the ingredient list of Scalpure once more, knowing what we now know about calcium bentonite, it becomes evident that its primary practical function in this product is as an emulsifier for the various essential oils, stabilizer, and viscosity modifier. However, in addition to these worthwhile and practical properties, the clay also acts as an exfoliant for the scalp and a detoxifier for the scalp and hair. The product makers claim that it is capable of removing toxins and metals below the skin’s surface, thereby improving the health of the hair follicles and thus increasing hair growth. While I can neither confirm nor deny that claim, I can state with a fair level of confidence that this is at the very least being accomplished on the surface of the scalp, which may be sufficient to lend improvement to a situation of an oily scalp, dry and flaky scalp, or one with buildup of toxins.

It seems to me that this product could be very useful for one to incorporate into the hair care routine. However, for the sake of curly hair, I might caution being too rough with the hair when the product is being applied or while it is on the hair. The reason for this caution is that the clay particles could possibly roughen up the cuticle if care is not taken in the handling of the hair when in contact with these particles. (Doesn’t it always seem to come down to the cuticle and its protection?”>

Another possible red flag I could see with these types of products for those with curly hair is the potential for the hair to become dried out, or essentially desiccated. Remember that calcium bentonite is hygroscopic and does attract water to itself (not to the extent that sodium bentonite does”>, so it is feasible that it could remove water from the cortex of the hair. Hair that is more porous would be more susceptible to this problem, so perhaps these consumers should use the product with caution or do a deep-conditioning treatment post-application. Leaving the product on for too long would also increase the potential for this phenomenon, so I recommend shorter exposures. I think for most people, with proper use, this product should be just fine and possibly quite beneficial.

By Tonya McKay · Published December 1, 2010

Dear Tonya: Why is it that some products formulated with “gentle” surfactants and marketed as natural or sulfate-free actually seem to be more drying and damaging to my hair? I thought these products were supposed to be more gentle and kind to my fragile curls.

A: This question pops up frequently, and I have asked it myself when trying out new products without having really scrutinized the ingredients list. (Yes, even the CurlChemist sometimes buys things without much regard for the ingredients list, simply because the products look nice, smell nice, or have good promises on the package”>. Several factors are at play here.

Concentration of Cleansing Agent

It is possible that some of these sulfate-free shampoos contain very high percentages of surfactant, resulting in a product that is more effective at removing fatty acids and dirt from the scalp and hair. This can be disastrous for hair that is already fragile and that struggles with being too dry already. Unfortunately, it is not possible to determine this information by reading the ingredients list, as the labeling requirement is simply that the ingredients are listed in order of concentration—typically highest to lowest. Thus, the first surfactant on the list could be in the formula at 10%, 20%, or even 30% (or anything in between”>, and it would not be evident to the consumer.

Lack of gentle co-surfactants

Many products formulated with some of the stronger surfactants contain additional detergents called co-surfactants. These are typically materials such as cocamidopropyl betaine, fatty alcohols, and mild cationic surfactants. The mixture of these various surfactants act to diminish both the potential irritancy of the product and the oil stripping capability. The micelles formed in such mixed surfactant systems exhibit different physical and kinetic behaviors than those comprised of a single surfactant. The result is typically a milder formulation. Some of the products advertised as more pure or more gentle actually leave this important step out of their formulation.

Lack of fats/oils/conditioning agents

Good-quality cleansing products include moisturizing agents in their formulation that help to redeposit some oils onto the surface of the hair to prevent excessive drying from the washing process. Again, some of the simpler products that claim to be gentle may be missing this important component of the formulation.

pH Level

Human hair has a natural pH (called its isoelectric point”> of around 4.5. Any product with a pH higher than that is therefore alkaline with respect to the hair, which makes it inherently more drying and damaging to the cuticle and the fatty acid layers on the surface of and within the cuticle. Many of the surfactants used for shampoos are stable only in a narrow pH range—often between 5-7. For this reason, the majority of shampoos are formulated to be around 6 on the pH scale. It is possible to obtain a gentler product by formulating it to have a pH of around 4.5 – 5.5, closer to the natural state of hair (pH = 4-4.5″>, but it must contain surfactants that are stable at that pH. These types of products will usually have citric acid or some other mild acid near the end of the ingredients list. You can order pH test strips if you want to check out some of the products in your bathroom yourself.

Some ingredients to look for when choosing a gentle or mild shampoo for your hair are:

• cocamidopropyl betaine and other betaine surfactants
• carboxylate surfactants
• sodium lauroyl lactylate, sodium caproyl lactylate
• sodium laurylglucosides hydroxypropyl sulfonate
• cocoglucosides hydroxypropyltrimonium chloride
• sodium cocoamphopropionate, sodium cocoyl isethionate, disodium laureth sulfosuccinate
• nonionic polymeric surfactants
• lauryl-glucoside sodium maleate crosspolymer, lauryl-glucoside sodium succinate crosspolymer, decyl-glucoside sodium maleate crosspolymer

In conclusion, it is important to remember that a shampoo is comprised of a number of ingredients meant to work together to achieve the goal of clean, manageable hair. The label does not reveal the entire story, but it can allow us to glean important clues as to whether a particular shampoo might be more or less inclined to strip our curls of too much moisture. A single ingredient (or lack thereof”> is not sufficient to predict the performance of a particular product, and the list of mild surfactants is in no way comprehensive. It is important to consider the total ingredient list, where one should be looking for not only certain types of cleansing agents, but also various combinations of different types of surfactants, polymers, oils, and other conditioning agents (humectants, vitamins, etc.”>. Physical properties such as pH also play a role in the mildness of a shampoo.

So, when selecting a new product, consider all of these factors in your evaluation. As always, if you find something that works for you and that you like, consider that to be your most valuable bit of scientific data and keep using it, even if the “science” says it might be harmful. In contrast, if the “science” says that a product should be good and gentle (i.e. “sulfate-free””>, but your hair responds poorly to it, listen to that information as well! Only you know what you want most from your curls.

By Tonya McKay · Updated May 28, 2024

Cleansing ingredients found in shampoos belong to a category of molecules called surfactants (surface active agents”>. These materials are comprised of both polar and non-polar segments. The polar segments are water soluble and are referred to as hydrophilic, which means water loving, while the non-polar segments are only very slightly soluble in water due to a lack of sites for favorable interactions with water molecules. The terms hydrophobic (water fearing”> and lipophilic (oil loving”> are used interchangeably to describe the non-polar portions. Since surfactant molecules possess both lipophilic and hydrophilic qualities, they are referred to as amphiphilic materials.

Frequently, the hydrophilic portion of the surfactant exists on a terminal end of the molecule, and for this reason, is often referred to as the head group. The hydrophobic segment of linear surfactant molecules is typically an alkyl- or aryl-containing chain, and is referred to as the tail group. (Figure 1.”> Other types of surfactants, such as bulkier small molecule surfactants with multiple or branched tails, amphiphilic polymers, and biological materials have a more complex molecular architecture that gives them various geometric shapes. Many of these may not possess a distinct head group and tail group, yet they do have definite hydrophilic and hydrophobic segments.

When surfactants are dispersed into water, they cluster together first at the surface of the water, and then at higher concentrations, they cluster together in the bulk of the water and form aggregates known as micelles. In these clusters, the non-polar portions of the molecule all huddle together in the middle of the micelle, while the polar portions form a sort of shield on the outer rim of the micelle, creating a hydration shell and segregating the hydrophobic portions of the surfactant from most of the water. These types of micelles (oil-in-water”> can absorb oil into their core and hold it there, while the hydration shell sort of holds the whole thing together.

Most surfactants used for cleansing hair and skin have a negatively charged ion at their head group (example: sulfate”> and a positively charged counterion (example: sodium”>. These are called anionic surfactants. Positively charged (cationic”> surfactants are typically used as emulsifiers to facilitate mixing of oils such as silicones and other polymers. Cationic surfactants are also attracted to the negatively charged surfaces of skin and hair, and so they can also be used as mild conditioning agents. Zwitterionic surfactants have both a positive and a negative charge. Some of these, particularly cocamidopropyl betaine, can be quite useful in shampoos and are oftentimes milder than some of the typical anionic surfactants. Nonionic surfactants generally have polar (but not charged”> segments with multiple oxygen containing moieties (such as ethylene glycol”> and can be quite gentle and effective as cleansing agents.

Representation of a linear surfactant molecule

When determining the relative strength of detergency (oil-stripping ability”> of a surfactant, one must consider a variety of things. The size and structure of the tail group is important, as is the size and structure of the polar head group, as well as the size and structure of the counterion (sodium, ammonium, etc.”>. These are complex properties described by concepts such as self-assembly, critical micelle concentration, packing parameter and the principle of opposing forces.

Essentially, the more compact the molecule and its head group, the more efficiently it can pack into micelles of larger size and capacity. Micelles that are larger can pack more oil into them—thus more efficient at removing oil from the scalp and hair (and other surfaces”>.

I am unaware if anyone has gone through and systematically tested and ranked a wide variety of surfactants for harshness on hair (would love a reference if something like that is published”>, but based on what I know of their structure, I can put forth some educated guesses as to relative harshness for some of the more commonly used materials. This is not a comprehensive list, and I am glad to offer opinions on any you come across that are not on the list (as the number of materials used is very large”>.

Also, remember that surfactant performance is affected by temperature, pH, concentration of the surfactants in the formula, addition of moisturizers to the formula, and concentration of other materials (such as addition of salts which provide counterions that can decrease repulsion between head groups and allow more surfactants to pack into a micelle and co-surfactants that perform similarly”> in the formulation, so this is a rough guideline at best.

Harsh Surfactants

• sodium laureth, myreth, lauryl sulfate: harsh, small molecule surfactants, with very small polar head group

• sodium coco sulfate: very slightly milder than sodium lauryl sulfate, but not much (made from coconut fatty acid and not purified, has some molecules with longer tail groups and some with shorter”>, similar to sodium laureth sulfate

• ammonium lauryl and laureth sulfate: very slightly less harsh due to larger head group (ammonium”>

• sodium C14-16 Olefin sulfonate: very harsh

• TEA lauryl sulfate: harsh, slightly less harsh than ammonium lauryl sulfate, (larger head group than sodium or ammonium versions”>

• TEA-dodecylbenzenesulfonate: irritant and can be drying if used in too high amounts in the formula

• sodium alkylbenzene sulfonate: harsh

• ammonium or sodium xylenesulfonate: fairly harsh

Some Gentler Surfactants

• sodium cocyl isethionate: extremely gentle

• cocamidopropyl betaine: mild surfactant, in part due to its zwitterionic character

• sodium lauryl sulfoacetate: large molecule surfactant, very mild, very gentle

• sodium cocoyl (or lauryl/lauroyl”> sarcosinate: very mild

• ethyl PEG-15 cocamine sulfate: very mild due to being a large molecule (PEG modified”>

• dioctyl sodium sulfosuccinate (also known as aerosol-OT or AOT”>: mild due to its branched structure

• sodium lauryl glucose carboxylate: very mild due to its large structure

• disodium laureth sulfosuccinate: very mild surfactant

• Sodium methyl 2-sulfolaurate/ disodium sulfolaurate: (synonym”> Sodium Methyl Cocoyl or Lauryl Taurate – mild, derived from coconut fatty acids

• sodium cocoyl glycinate: mild

• Pluronic and Tetronic surfactants (gentle, nonionic, biodegradable polymeric materials”>

• polyglucosides: very mild, nonionic sugar-based surfactants

• poly decyl glucoside carboxylate: very mild non-sulfate surfactant

By Tonya McKay · Published September 7, 2010

I share the frustrations of many of you when it comes to understanding hair products and how hair responds to them. Entirely too often it seems to me that luck or fate have more to do with the mythical condition known as “a good hair day” than anything else. Of course, as a scientist, I know that simply isn’t the case, but it seems impossible (translate: entirely too much effort”> for me to analyze all the variables and reliably achieve that elusive state of perfect balance. Why can’t we just formulate products that perform predictably and reliably—this isn’t rocket science, is it? Maybe that is a good question.

The fact is that a huge number of factors influence the behavior and texture of our hair: outside temperature, humidity, dew point, hair texture, hair condition (chemically or thermally treated?”>, type of products used, order in which products are used, handling of the hair, water quality, etc.. None of this even takes into account the many ingredients in the products we use, and how those ingredients might interact with one another, with your hair, or with the local climate. It is mind boggling and daunting to even the best researchers.

Thus, it seems ironic that in the scientific world, cosmetic and personal care chemistry are often treated with skepticism and have a reputation for being poor science. Despite all that I know of the many principles involved in the development of hair and skin care products, I must confess to having made this accusation myself a time or two, even toward my own projects. My biggest complaint in graduate school was that I just couldn’t get in there and ask those molecules what they were doing!

What’s Bad in Cosmetic Science?

There are some reasons for people having this dim view of the industry. Misleading marketing and outright charlatanism are unfortunately prevalent in the field, with outlandish claims often made without proper data to back them up. Statistics are abused and misrepresented to give the appearance of remarkable results. Preying upon the fears of consumers with heavy-handed ‘safety’ information is also a technique used to convince people to avoid certain products and to purchase theirs.

Other practices in the industry, usually at smaller companies with fewer resources, such as haphazard formulation, inadequate quality control, and insufficient stability testing of new products and raw materials, can erode the trust of consumers and scientists alike. Formulating without a solid grasp of concepts such as emulsion stabilization, viscosity modification, and preservation can result in unpredictable shelf life of a product and also in inconsistent results in application. Extensive testing is necessary to evaluate a product every time the formula is changed, but it is frequently foregone.

Another criticism of the field is that new findings are not always published in peer-reviewed journals, as the data and information are considered proprietary. This helps companies maintain an advantage in an incredibly competitive market, but it can lead to skepticism from anyone who thinks to question their claims. However, there really is excellent and highly scientific work being published by researchers in this area, not only in the trade journals of the field, but also in more academic publications such as “Langmuir,” “Macromolecules,” “The Journal of Physical and Colloid Chemistry,” and others. Patents can also be great sources for information.

What’s Good in the Cosmetic Science?

Innovation and achievement of lasting success in this competitive market requires a strong commitment to fundamental scientific research, with high levels of interdisciplinary expertise and collaboration between experts in various fields. Consumer product companies such as Unilever, Procter & Gamble, Living Proof, Estee Lauder (and many others”> devote millions of dollars to doing the highest level of science in order to maintain or grow their market share. Raw material suppliers do the same, and commercially-funded university studies are ongoing worldwide and involve the latest technologies.

Some of the scientific disciplines utilized in the research and development of new personal care products are:

• Biology (understanding hair and skin”>

• Microbiology (prevention of microbe growth in product”>

• Colloid science (understanding mixtures of waters and oils”>

• Physical chemistry

• Biochemistry (proteins, fats, cell membranes”>

• Nanotechnology

• Polymer science (synthesizing new polymers for specific uses, understanding how polymers behave in formulas and in situations”>

• Processing and engineering (scale-up of a product from lab to commercial production”>

• Biotechnology

• Water chemistry (understanding pH, hard water/soft water and the impact that has on products”>

• Analytical chemistry and materials characterization (evaluation of raw materials and finished products, including development of novel ways to emulate and evaluate how the product will be used”>

Advances in the fields of polymer science in particular have given cosmetic scientists many new ingredients to work with, capable of providing exciting new benefits in the areas of styling, conditioning, moisturizing, and product thickening. Vitamins, herbal extracts, nanoparticles, and other additives have also been gaining popularity with formulators.

Formulators who have added new ingredients to products frequently left many of the old ingredients in the formula. No one wanted to run the risk of decreasing the efficacy of a product or of alienating consumers by changing the product too much. Unfortunately, this led to huge ingredient lists that are expensive to manufacture and final products with very complex behavior. The statistical probability of a complication or problem arising increases with the addition of each new variable. Each new ingredient added to a formula brings with it the potential for interaction with other ingredients, sometimes causing unfavorable results.

In an interview at the Chemists Corner, Dr. Johann Wiechers, an accomplished scientist in the field of skin delivery of biologically active ingredients, discussed how advanced technology is enabling cosmetic scientists to explore the fundamentals of their work at a molecular and mechanistic level. Sophisticated analytical techniques, increased computational capability, and systematic experiments augment knowledge and in some cases have changed ‘the rules’ completely. Hopefully, scientists will use this information to develop new formulas using fewer ingredients, limiting them to the use of only those strategically selected, high performance components. If you care to delve further into this topic, Dr. Wiechers has written a series of articles on the topic, “Is Cosmetic Science Really ‘Bad’?”

In closing, despite its occasionally shaky reputation, I remain in awe of the complexity involved in developing a really good hair or skin care product. While there is certainly an element of art to the development of hair and skin care products, it also incorporates the highest levels of many scientific disciplines

The development of tools by which we can characterize and understand the behavior of cosmetic ingredients and how they interact with skin and hair will inevitably lead to new discoveries and products in the future. As scientists with expertise in different areas continue to collaborate, the consumer will benefit by having access to products specifically targeted to different needs and that provide consistent results. I look forward to reaping the benefits of this work!

By Tonya McKay · Published August 9, 2010

Polyquats are cationic polymers, meaning they have positive charges along their backbone or pendant to the chain. They are highly effective as both hair conditioning agents as well as styling agents. These types of molecules can be quite complex in their behavior, and are a subject of extensive study in various fields, including cosmetic science. For this reason (and because I’m a polymer nerd”>, I find them sufficiently intriguing to revisit the topic fairly often, examining different aspects.

Here at NaturallyCurly.com, we get a lot of questions about polyquaternium ingredients, particularly regarding their removability from hair. Most recently, I read a discussion where the theory was put forth that as long as the polyquaternium number was sufficiently low (say, below -40″>, then the polymer is fine for use in a shampoo-free or mild-surfactant hair cleansing routine.

Figure 1. Illustration of cationic polymers. a.”> linear polymer with charges along the backbone, such as Polyquaternium-10; b.”> a comb-shaped polymer, with positive charges pendant to the backbone, such as Polyquaternium-4.

Actually (and perhaps unfortunately,”> it is a misconception that one can determine the compatibility of a polyquat and a low-poo method based upon its INCI (International Nomenclature of Cosmetic Ingredients”> designation number. This is a logical misunderstanding of how these materials are named. INCI assigns a number to a polymer as it is presented for inclusion into the materials database, in order of submission.

The naming is sequential and is unrelated to molecular structure, molecular weight or charge density. One has to look up the specific polymer in order to obtain its structure. Many of them are structurally quite similar, with various modifications along the backbone, such as the multiple variations of modified cellulose polymer. There are also polyquats made of guar gum, and many others made of various synthetic polymers and copolymers.

Another point of confusion is that the numeric INCI designation does not provide any information regarding the molecular weight of the polymer (the size of the polymer”>. This property can be quite influential in the performance of the cationic polymer, particularly when it comes to deposition onto the surface of the hair. (Gruber et al, 2001″>. But the tricky thing for label-readers is that polyquaternium-4 (and all the other cationic polymers”> can come in a variety of molecular weights, and there is no way to know which polymer is present without consulting the manufacturer (presuming they would even disclose such information”>. This could explain why people often observe that they get inconsistent results in very similar products (according to their labels”> containing polyquaternium-4 (or -10, or -32, etc.”>. The polymers may be of substantially different molecular weights, resulting in very different product performance.

Water solubility and build-up:

Cationic polymers can be completely water soluble, or they can be merely water miscible, depending upon things like polymer structure, molecular weight, and charge density. The critical thing to remember is that these polymers perform well as conditioning and styling agents because they are attracted to and adhere to the surface of the hair due to electrostatic interactions (the positively-charged polymer is attracted to the negatively charged portions of the cuticle”>. The complex that is formed is often very strong, and the interactive forces can be difficult to overcome using conventional methods. A small anionic surfactant such as sodium lauryl sulfate may not be sufficient to overcome that attraction and remove the polyquat.

Polystyrene sulfonate has been found to aid in removal of these polymers from hair, but it is not an ingredient often seen in shampoos. Clarifying shampoos may also not be effective in removing all polyquats from hair. However, some polyquats seem to respond well to traditional shampoos. For instance, researchers at BASF found that polyquaternium-10 is removable with an anionic surfactant.

My personal hunch is that removability is dependent upon the charge density of the polymer (how many positive charges exist along the backbone”>, its overall structure, and also the state of the hair to which it is applied (more damaged hair has a higher negative charge density, and so would provide a cationic polymer more sites with which to bind tightly”>. For instance, PQ-10 is a cellulosic derivative, which is very water soluble due to its ether (oxygen-containing”> components, which allows for fairly easy removal.

Build-up is also affected by polymer structure. Polyquaternium materials based upon guar gum are more difficult to remove from hair and also display a greater tendency to accumulate on the hair with repeated usage. Polyquaternium-4 is a cellulosic derivative, but with a fairly high charge density. It is extremely substantive to hair and very useful as a styling agent, but has been found to exhibit very little tendency to build up.

I have this other hypothesis that mechanical forces—brushing, washing, combing and styling—are eventually sufficient to detach some of these polymers from the hair. This may be what BASF researchers were seeing when they noticed their new polymer PQ-44 performed very well as a detangler, but did not demonstrate any tendency toward build up. The authors believe that the polymer adheres to the surface of the hair at a few points of the polymer, while the uncharged ends of the polymer form loops that are not flat on the polymer surface. These loops reduce friction between adjacent strands, but also may provide the means for ease of removal later when the hair is washed.

To Polyquat or Not?

In closing, I hope it is more clear now that one cannot rely upon the number of a polyquaternium to determine its removability with any degree of certainty. One has to refer to the INCI database or another source to obtain the exact structure of the polymer in question. Once the structure is known, one can then make certain assessments of its properties.

Although I have seen a few sweeping denunciations of polyquats by some curly hair experts, my personal opinion is that there are certain polyquats that can be advantageous to use in the care and styling of curly hair.

The angled hexagonal structure in combination with the oxygen bonds in the center of the molecule make PQ-10 good for your hair, obviously.

The data indicates that PQ-4, PQ-10, and PQ-44 do not create problems with buildup if one uses a mild shampoo, and each can provide good benefits either in conditioning or styling. There are others that cause more problems with build-up, such as PQ-11 and guar hydroxypropyltrimonium chloride. One recent question was about PQ-37, and while I cannot find specific data on its removability at this time, it looks potentially problematic to me based upon its structure.

As always, choose your products carefully, get samples when you can, and see what works for your hair.