Changing the Shape of Hair 178 Permanent Wave Formulations The two most common systems for permanent waving are based on either ammonium thioglycolate (ATG) or glycerol monothioglycolate (GMT).23 ATG formulations typically contain 7–9% ATG, nonionic surfactants to help wet the hair and a chelating agent.23,33 Dithiodiglycolate may be added to help reduce hair damage. Ammonia is typically used to adjust the pH to between 9.2 and 9.5. Higher concentration and/or pH will produce a stronger waving action and control of pH is critical to give the consumer the expected wave strength without danger of over-processing. Cysteamine can also be utilized and a reducing agent in permanent wave formulations.23 GMT perms must be mixed just prior to use, as GMT is not stable in solution. They can function with or without added heat. The pH is typically between 7 and 8 and they are often referred to as “acid perms.” GMT perms can produce excellent results with less hair damage than ATG perms, but they are slower and the requirement for premixing tends to restrict their use to salon products. Cysteamine can also be used as a reducing agent in permanent waving formulations, but it is currently much less common than either ATG or GMT. Oxidizing agents used in “neutralizers” may include hydrogen peroxide, perborates, ammonium persulfate, and sodium or potassium bromate. Hydrogen peroxide is the most common choice.23,33 While hydrogen peroxide is more active in a neutral and alkaline medium than in acid media, the stability of the hydrogen peroxide is maximized at ~ pH 3–4 and neutralizers are typically formulated in this pH range. Stabilizers such as phosphoric, tartaric, and/or citric acid may be are also be added to the formula. The water used must be absolutely free of any iron or metal traces. Bisulfite based “body waves” were popular at one time, but bisulfite currently sees little use in permanent waving products because of its low efficacy in producing a wave. Detailed examples of modern permanent wave and neutralizer formulations are covered by Wickett and Saviades.23