The first cold wave's active ingredient belongs to which chemical family?

• A. Thioglycolate acid or derivative
• B. Carboxylic acids
• C. Amines
• D. Alcohols

Answer: (A)

Cold waves rely on a reducing agent to break the hair’s disulfide bonds so it can be reshaped. The active ingredient in the first cold wave is a thioglycolate compound—thioglycolic acid or one of its salts/derivatives (such as ammonium thioglycolate). The sulfhydryl (-SH) group in these compounds donates electrons to break the disulfide bonds in keratin, loosening the structure so the hair can be wrapped and reformed around rods. This specific chemistry comes from the thioglycolate family, which is why it’s the best fit. Other groups—carboxylic acids, amines, and alcohols—don’t provide this disulfide-bond–reducing action essential for a cold-wave perm.