In 1938, Arnold F. Willatt invented the cold wave, the precursor to the modern perm. It used no machines and no heat. The hair was wrapped on rods and a reduction lotion containing ammonium thioglycolate was applied. This chemical breaks open the disulfide linkages between the polypeptide bonds in the keratin (the protein structure) in the hair. The disulfide bonds give hair its elasticity, and can be reformed with chemicals. Next, an oxidation lotion was applied, (hydrogen peroxide), to close the disulfide bridges again and the hair was reformed to the shape of the rod. The entire process took 6–8 hours at room temperature. In the 1970s, acid perms were invented. These use glyceryl monothioglycolate instead and contain no ammonia. They are sometimes called buffered waves. This perm is slower but gentler to the hair. Heat is usually added by placing the client under a dryer, after covering the wrapped head with a plastic cap. The reaction is endothermic and the additional heat causes the pH to rise from 6.9 to 7.2. Perms today use this method with sodium thioglycolate instead of ammonium thioglycolate, at a pH of 8 to 9.5. This method takes only 15–30 minutes until the neutralizer is applied to bring down the pH and rebond the hair. Other types of modern perms include exothermic perms, which are self timing and self heating; and neutral, or low pH, thioglycolate free perms. Digital perms were introduced in the 21st century and in use especially in modern Asian cultures. The process was patented and invented by a Japanese company, Paimore Ltd. -------------------------------------------------
There are two parts to a perm: the physical action of wrapping the hair, and the chemical phase. Both of these can affect the result. Important physical variables involved are what type of rod is used, how the hair is wrapped and how end papers are used. The two most common types of rods are straight and concave; each giving a different curl effect. The wrapping method is either spiral or croquinole, and various types and positionings of end papers can be used with any combination of the above. Generally, smaller rods will produce smaller, tighter curls and increase the appearance of shortening the hair. The chemical solution used in the perming process is determined by the client's hair type and the pH of the solution. Classic alkaline perms are used for stronger, coarser hair. They work at room temperature and usually contain ammonium thioglycolate in the pH range of 9-10. Acid perms are used on more delicate or thinner hair. They require outside heat application and usually contain glycerol monothioglycolate in the pH range of 6.5-8.2.
Permanent wave machine invented in 1928 by Marjorie Joyner — The first African American woman to receive a patent -------------------------------------------------
Due to the harsh nature of the chemicals, it is important that contact with the skin be minimized. Modern chemicals are less irritating, but measures should still be taken to reduce contact with anything other than hair. A poorly performed permanent wave will result in breakage of the disulfide...