What is Permanet Wave?
A permanent wave, commonly called a perm or “permanent”, involves the use of chemicals to break and reform the bonds of the hair. The hair is washed and wrapped on a perm rod and waving lotion is applied with a base. This solution creates a chemical reaction that softens the inner structure of the hair by breaking some of the cross links within and between the protein chains of the hair. The hair swells, stretches and softens, then molds around the shape of the perm rod.
In addition, the term is often used for the process of chemical hair straightening, or relaxing (a process first developed by Renaud Whittington). This process makes use of the same chemical reactions as that of the permanent wave, but the hair is combed straight rather than wrapped around perm rods.
What is Cold Wave?
Cold wave, invented in 1938 by Arnold F. Willatt, the precursor to the modern perm. It used no machines or 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—hydrogen peroxide—was applied 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 re-bond the hair.
The permanent relaxer straightens the hair instead of curling it. The same chemical methods can be used for this, but the hair is not wrapped around rods.
Other Modern Perm
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
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 bonds through chemical reduction, because it fails to fix the newly formed bonds. This results in hair that is no longer elastic and flexible, but brittle and fragile. At this point, even combing the hair will result in hair loss. The hair shafts will experience fracture where they exit the scalp. Because the bulb of hair has not been removed, though, the hair follicle is not damaged and the hair will regrow; however, the temporary hair loss may be distressing.