Which chemical is commonly used for permanent wave procedures?

Ammonium thioglycolate is the chemical commonly used for permanent wave procedures due to its ability to break and reform the disulfide bonds in the hair's keratin structure. This process allows the hair to be reshaped with a curl or wave pattern that can be set and last for an extended duration. The alkaline nature of ammonium thioglycolate helps to swell the hair shaft, making it more pliable and receptive to the desired shape.

In contrast, hydrogen peroxide is typically used as an oxidizing agent, primarily in hair bleaching or coloring processes, rather than in perming. Alcohol is primarily a solvent and does not perform any of the chemical reactions required for permanent waving. Silicone is often used as a conditioning agent in various hair products but does not play a role in altering the hair's structure for permanent waves. Therefore, ammonium thioglycolate is the correct choice for its specific properties and function in permanent wave procedures.