Which chemical is used to create a permanent wave in hair?

Ammonium thioglycolate is the chemical used to create a permanent wave in hair due to its ability to break the disulfide bonds in the hair's keratin structure. This process allows the hair to be reshaped into curls or waves once the solution is applied. After the desired wave is achieved, a neutralizing agent is applied to reform the disulfide bonds in their new configuration, ensuring that the hair maintains its new shape.

Hydrogen peroxide is primarily used as a bleaching agent or a developer in hair coloring processes, rather than for creating waves. Ethyl alcohol serves mainly as a solvent in various cosmetic formulations and does not have the properties necessary for initiating a permanent wave. Glycolic acid, while an exfoliant and useful in skin care, does not play a role in hair perming processes. Therefore, the specific properties of ammonium thioglycolate make it the ideal choice for creating permanent waves in hair.