Curly perms for African American hair types exist, and they are often referred to as a double-processed style. This is because there are two different chemicals used during the process.
The initial step of a curly perm consists of the application of a chemical called ammonium thioglycolate, or "thio" for short. This chemical relaxes the hair and removes the natural curl. Once the hair has been processed with the thio, it is set in perm rods, or curlers. Then, a waving or reshaping solution is applied. When the hair is set into its new curls, a neutralizer is applied, which uses oxidation to set the style.