Damage: October 2008 Archives

There are a wide array of styles and textures available to today's salon clientele. With so many options, the ability to switch from one look to another has never been more important.

To answer the question--can relaxed hair be stripped?--it is necessary that we first understand the chemistry of the hair, as well as the lanthionization (relaxation) process.

When two or more polypeptides align themselves parallel to each other, and their cysteines (amino acid) combine with each other to form cystine or disulfide bonds across these polypeptides, a keratin fiber is created in the process.

Hair, or keratin according to chemical terminology, is made up of polypeptides. (Polypeptides are made up of amino acids -- the basic unit of protein.) Polypeptides are aligned in a parallel fashion and are cross linked with cystine bonds (also called disulfide bonds). Note that cystine bonds have two sulfur atoms.

When excessively curly hair is chemically straightened with hydroxide-based relaxers, (i.e., sodium, potassium, lithium, and guanidine hydroxide, etc.) approximately one-third of the cystine bonds are changed to lanthionine bonds. The lanthionine bond has only a single sulfur atom; one sulfur atom less than the cystine bond of virgin hair.

The folks at Nalco Company (Yin Hessefort, Brian Holland, and Richard Cloud) published an interesting study that appeared in the July/August issue of the Journal of Cosmetic Science, where they studied the porosity characteristics of damaged hair.

The study used the gas sorption method to determine the total pore volume, adsorption pore-size distribution, and the surface volume of the damaged hair. The two types of damaged hair they looked at were bleached hair and hair that had been exposed to UV rays.

What they found was that bleached hair nearly tripled in surface area during the first minute of bleaching due to an increase in the number of pores, followed by a sudden drop after 10 minutes of bleaching, suggesting that smaller micropores (< 2 nm) break down into larger macropores (> 50 nm). In contrast, they found that UV damaged hair showed an immediate loss in surface area during the first 200 hours of exposure and a gradual increase as exposure time continued, which they theorized was caused by a fusion of cuticle cells followed by an increase in pores or cracks.

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