Altering Chemical Bonds in Hair
In unit 1 we learned about different types of bonds, one of which being hydrogen bonds. Hydrogen bonds as well as disulphide bonds are in the keratin protein in hair.
Hydrogen bonds determine the texture of an individual’s hair; if it is curly or straight. When in contact with water the hydrogen bonds in hair break thus allowing hair to loose some natural texture when wet. Hydrogen bonds are the reason why hair goes back to its natural texture as it dries and the bonds reform.
Within the keratin in the hair’s protein there are naturally occurring disulphide bonds. These bonds form between sulphur molecules in the keratin. Disulphide bonds are responsible for the strength of a person’s hair texture. It is these bonds that are broken in the process of relaxing curly hair to make it permanently straight. In order to break a disulphide bond one of the sulfur atoms in a bond must be removed. By doing so, a more flexible bond called a lanthionine bond is produced. The loss of the sulfur atom weakens the connection between individual hairs which then allows hair to be altered. Chemical relaxers are what alters the hair to make it straight.
On the left is a disulphide bond and on the right is a disulphide bond with a sulfur atom removed, also called a lanthionine bond.
In order to break the strong disulphide bonds and alter hair’s texture the relaxers also need to be very strong. As we learned in unit 2 and again in unit 4 the pH scale can be used to measure how acidic or basic a substance is. The pH scale ranges from 1-14, with 7 being neutral substances. The lower on the pH scale a substance is the more acidic it is, and the higher on the pH scale a substance is the more basic it is. Chemical hair relaxers are more basic ranging usually from a pH of 9-14. Most hair relaxers are solutions of sodium hydroxide (NaOH) or potassium hydroxide (KOH). After the use of the basic relaxer a neutralizer is used to return the hair to a normal pH of about 5. The neutralizer also rebonds the hair into a straight form.
There are concerns regarding the use of strong chemical hair relaxers as they have the ability to burn the scalp. The mistake very often made is that the individual relaxing the hair does not consider the temperature in the room when the relaxer is put on the hair. If the temperature in the room increases the chemical reactions in the hair will occur quicker. This therefore means that often the relaxer is left on too long after the chemical reactions have occurred.
I personally am surprised by how seemingly easy it is for someone to alter the bonds in their hair. All you need to do is make a hair appointment or buy an at home relaxer kit. I am also concerned about how easy it is to buy the chemicals. They have the ability to burn the scalp and are easily accessible to possible first time users who have a higher risk of burning themselves.
Question: Do you think at home hair relaxing kits should be sold or should only professionals educated on the chemistry of the chemicals be able to purchase them? Why?