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WHAT'S THAT STUFF? - Hair Coloring
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April 15, 2002
Volume 80, Number 15
CENEAR 80 15 p. 42
ISSN 0009-2347
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Most of us take clean hair for granted, but there's more to it than 'lather, rinse, repeat'



I convinced my mother that my teenage life would be over if I didn't wash my hair with Herbal Essence shampoo. It was the early '70s, and I was a sucker for the picture Clairol created with their advertising. That would be me with the flower garland in my flowing hair, as lovely a young lass as could be. I bought--well, cajoled my mom into buying--the image.

That's exactly what companies that produce and market shampoos are counting on, even more today than 30 years ago. Just walk down any store's hair care aisle: The array of products is staggering. I can select from any number of shampoos that will tame my curls, "release" them, "volumize" them, hydrate them, strengthen them, or control their tendency to frizz.

But what if I just want to wash them? How do I pick a shampoo that will leave me with clean hair?

Well, I'm in luck, because most of the products on those crowded shelves will clean my hair. That's a no-brainer for shampoo producers: Add a little surfactant--foaming and cleaning agent--to a lot of water, throw in some conditioning agent to temper the not-so-pleasant aspects of the surfactant, and they've made shampoo. I could do it in my kitchen if I were so inclined. But I'm not, and I also wouldn't buy the crude shampoo I just described. It wouldn't smell appealing, feel smooth as I worked up a satisfying head of lather, nor leave my hair static-free and shiny. Hmmmm. Maybe I want more than just clean hair, after all.

How does a company go about making shampoos that turn our hair--each of which is a shaft of dead proteins once it leaves its root--into vibrant, thick, shiny, bouncy, manageable manes, and, according to their ads, simultaneously change us into happier, self-assured, outgoing people.

Surely no simple concoction can achieve so much, and the list of ingredients on the back of a shampoo bottle attests to that. In the U.S., the Food & Drug Administration requires that all ingredients be listed in order of descending concentration and that the ingredients be listed by chemical name, because, it says, "that's what they are." So, for example, if vitamin E is used in a formulation, it is listed as tocopherol. A company may request that FDA grant "trade secret" status to a proprietary ingredient; if granted, that specific ingredient is not listed, but the product label litany ends with "and other ingredients."

In the language of the personal care industry, companies build shampoo systems. The formulators start with the surfactants, which can be anionic, cationic, nonionic, or amphoteric--but what they all have in common is a polar hydrophilic head with at least one long-chain hydrophobic tail. Shampoos generally contain suites of surfactants that act synergistically--each has its own role, but they also work in concert to improve the overall formulation.

Some anionics commonly used in shampoos are sodium lauryl ether sulfate (also called sodium laureth sulfate), sodium lauryl sulfate, and the ammonium versions. The anionic surfactant is the primary foaming and cleansing component of a shampoo.

Olealkonium chloride, distearyldimonium chloride, and isostearyl ethyldimonium ethosulfate are cationic surfactants that are used in some shampoos. Cationics like these provide some conditioning to the hair, and they also can boost the viscosity of the shampoo formula.

Amphoterics such as cocamidopropyl betaine or cocamidopropyl hydroxysultaine provide foam stabilization and viscosity-building properties.

Nonionics such as polyethylene glycol (PEG) esters can play a number of roles in a shampoo system. For example, PEG-80 sorbitan laurate promotes mild cleansing, whereas PEG-150 distearate is used to build viscosity. Alkanolamides--one you might see listed on a label is cocamide MEA--is an example of another type of nonionic that provides foam stabilization and viscosity-building properties.

Surfactants clean hair by stripping sebum from hair shafts. Sebum is the natural oily coating that tends to collect dirt, styling products, scalp flakes, and the like. It is attracted to the hydrophobic end of the surfactant, then washed away when a shampooer rinses. Surfactants determine how gently hair will be cleaned--harsh cleaners can overstrip hair and dry skin.

FORMULATORS also consider ingredients that will provide other characteristics. Glycol stearate or glycol distearate will impart pearlescence to a shampoo system; ethyl alcohol, glycerol, or sodium xylene sulfonate can be used to maintain clarity; and a small amount of a resin latex can be used if an opaque shampoo is desired. Formulators will add thickeners (cocamide monoisopropanolamide or sodium chloride or citrate, for example) and conditioners (dimethicone or quaternized cellulosic polymers) to achieve the right "feel" in the shampoo and on the cleaned hair, respectively.

Conditioners can also help with static control. Shampoo makers may add a sunscreen or a humectant--to help retain moisture--and they'll add preservatives and antioxidants. Fragrances and dyes will be incorporated. Formulators may also consider using foam stabilizers (betaines or amine oxides) or chelators to tie up trace ions that can complex with fragrance components and dyes.

And formulators have to ensure that the pH is within a workable range, some say 5.5 to 6.5. Correct pH is important because the cuticle of the hair, which is exposed after the sebum is stripped away, is covered with overlapping scales that are smoothed and soothed in a properly acidic environment. Aggravated scales don't overlap nicely, and they make hair look dull and feel rough. They can also snag other raised scales on neighboring shafts, resulting in snarls.

Getting the ingredients and proportions right is a matter of experience if formulators are using tried-and-true ingredients or trial and error if they are moving in new directions. They need to end up with a formulation that has all of the desired attributes for the consumer as well as being processible, stable, and within budget.

Formulators can tweak shampoo in a wide variety of ways, but it's up to the marketing experts to create an image for their shampoo that will make people actually look for it among all the contenders--and maybe even remember it 30 years later.


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Copyright © 2002 American Chemical Society

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