Permanent waving process

One purpose of these studies was to try to achieve essentially complete reduction of a smaller cross section of the hber and to determine if effective permanent-waving could still be achieved. A potential advantage to this type of process is to lessen cortical reduction and thereby to lessen cortical damage to the hair (the region primarily responsible for tensile properties) during the permanent-wave process. 

Normal hair is slightly acidic. In fact, the pH of hair is between 4.5 and 5.5. Hair that becomes too alkaline dries out, tangles easily, becomes dull, and generally looks damaged. Chemical processes, such as permanent waves, hair coloring, and bleaching, as well as a person s natural body chemistry, can all raise the hair s pH. 

Disulfide bridges are commonly manipulated in the process of giving hair a permanent wave. Hair is composed of protein, which is made rigid and tough partly by disulfide bonds. When hair is treated with a solution of a thiol such as 2-mercaptoethanol (HS — CH2—CH2—OH), the disulfide bridges are reduced and cleaved. The hair is wrapped around curlers, and the disulfide bonds are allowed to re-form, either by air oxidation or by application of a neutralizer. The disulfide bonds re-form in new positions, holding the hair in the bent conformation enforced by the curlers. 

Acid-balanced permanent-wave lotions contain monothioglycolic acid. Normally, acidic lotions penetrate the cuticle only slightly. That s why the process takes a longer time and requires heat in order for curls to develop. The advantages of the acid-balanced wave are that it forms softer waves, is more easily controlled, and can be used for delicate hair or hair that has been colored. 

Because reduction of the disulfide bond and its subsequent reactions is vital to several important cosmetic products, a large amount of research that is relevant to these chemical processes has been conducted. This chapter is concerned with reducing the disulfide bond in hair by mercaptans, sulfites, alkalis, and other reducing agents. Reactions of reduced hair are also considered, followed by a discussion of water setting, set and supercontraction, and swelling of hair, processes especially relevant to permanent waves, hair straighteners, and depilatories. 

Products and Uses The active chemical in depilatories (hair removers), permanent wave solutions, and hair-straightening products. Used in hair-curling, removing, and processing products. 

Like feathers and hair, wool consists mainly of keratin. This polypeptide contains L-cystine which is the oxidised (disulfide) form of L-cysteine. The former acts as a cross-link which determines the crimped nature of wool. In human hair this process is, of course, carried out reversibly in permanent waving ... 

FIGURE 1 5.18 Permanent waving, a chemical oxidation-reduction process. 

Uses Antistat, hair conditioner in cosmetics in thioglycolate permanent waving sol ns. to reduce processing time and condition hair in... 

The fermentation process can be artificially controlled and impeded by the addition of sulfur dioxide or potassium metabisulfite. The addition of this preservative poses a potential health hazard. The residual sulfites present in wine have been known to elicit urticaria, asthmatic reactions and respiratory failure. In the United States, since 1987, warning labels indicating the presence of sulfites must appear on wine bottles containing at least 10 ppm of sulfites (Fisher 1997)- In addition to their importance in wine making, sulfur dioxide and sulfites are used as food additives for their antimicrobial effect. Contact dermatitis to potassium metabisulfite has developed in a pharmaceutical worker (Nater 1968) and may also occur in bakers, from occupational exposure to flour (Apetato and Marques 1986), and in hairdressers to permanent wave solution, but has not been reported in winemakers. Sulfur dioxide has also been reported to cause contact urticaria (Maibach and Johnson 1975). 

In addition to its usefulness in the manufacturing and processing of protein ingredients, reactivity of disulfide bonds is the basis of the specific action of some particular protein derivatives in permanent-waving treatments (see Section IV.C). 

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