Hair is made up mainly of proteins and is pretty strong stuff. However, chemical processes can weaken your hair and cause it to break. In this article I’ll explain how the pH of hair products can affect your hair’s condition and how you can avoid unnecessary damage. The structure of the hair is made of two main parts. The outer layer, called the cuticle consists of overlapping scales which protect the cortex underneath. When your hair becomes damaged the scales of the cuticle can stand out or break off, exposing the cortex and making your hair feel dryer and harder to brush.
The cortex which is in the inner region of the hair is made of a string of proteins and gives the hair it’s strength and elasticity. This is why damaged hair does not return to shape or even snaps when stretched. The cortex is where melanin (which denotes your natural hair color) can be found. For this reason most hair colors will need to penetrate to the cortex in order to change your hair color. You can measure the pH of anything that is water soluble.
The pH indicates how acid or alkaline a substance is. The scale ranges from 0 to 14 with 0 being a very strong acid and 14 being a very strong alkali (aka a base). Both strong acids and alkalis should be avoided as they will burn skin. Water has a pH of around 7, as does Peroxide and most shampoos. Lemon Juice and Vinegar, both acids, have a pH of around 2 or 3 and baking soda, an alkali, has a pH of around 8 or 9. Hair Colors are Usually Alkaline Most permanent hair colors are alkaline. When an alkaline substance is applied to hair it opens up the cuticle. With hair color this allows the mixture to penetrate to the cortex where it can react with the hair’s pigment molecules to produce a color change. Permanent colors have a pH of around 7-8. With bleach the color molecules are oxidized, producing the lightening effect.
Bleach usually has a pH of around 8 or 9 and if used too often or mixed too strong it will cause the scales in the cuticle layer to break off which causes permanent damage. The layers in the cuticle will no longer lie flat and will stick outward causing hair to snag and tangle. When the scales do not lie flat or when some have broken off the hair is no longer water proof and the cortex is exposed to washing and environmental factors. This will cause it to dry out and loose elasticity leaving the hair prone to breakage. However, you can avoid most of this damage if you only bleach your regrowth each time and do not allow the bleach to overlap onto already bleached hair. Since peroxide has a pH of 7 all the alkalinity comes from the powder. If in doubt mix your bleach to a thinner consistency with more peroxide and avoid lumps of powder which can cause breakage. If you use a lot of powder the bleach is going to have a high pH which causing damage to the hair.