pH value plays a key role in hair care and in the correct use of hair products. pH value is a measure of hydrogen ions (grams per litre) in a solution. This is translated to a scale of between 0 and 14. pH value 7.0 is considered neutral, all values below neutral are acidic and all values above are alkaline.
As the pH value moves to either extreme - acid or alkaline - the solution will become stronger and more caustic. Extremely high acid or alkaline will damage or destroy hair! An acidic solution has a positive electrical charge (+) and an alkaline solution has a negative electrical charge (-).
Normal, healthy hair has a pH value of between 4.5 and 5.5 and is therefore considered acidic. Hair in this state will be positively charged (+) and has a compact cuticle structure. The outside cuticle layer is closed and smooth, promoting a natural, healthy shine. The internal cortex is protected and moisture levels are maintained, ensuring good strength and elasticity. Healthy hair has even, normal porosity and provides a good base for chemical services.
Damaged hair has a pH value above 7.0 and is negatively charged (-). The cuticle layer is raised with a dull/matt surface. The raised cuticle layer can catch, resulting in tangled hair with a high susceptibility to mechanical damage caused by combing or other external influences. In addition the cortex will be exposed to further damage, in danger of losing essential moisture and becoming dry/brittle. Damaged hair will be very porous and provides a poor surface for chemical treatments, with potentially uneven results.
As the majority of hair products are a solution containing hydrogen ions - for example water (containing hydrogen and oxygen) is often used as a solvent - it follows that they will have a pH value. This will influence the condition of hair. Care products are predominantly acidic and have an astringent effect on the hair, closing the cuticle layer. Shampoos will typically have a pH value close to the hair's natural level - promoting gentle cleansing - whereas conditioners and treatments have a higher acid value, helping to return damaged, alkaline hair back to a normal, healthy condition.
Chemical treatments, such as a bleach, perm or colour, are deliberately alkaline, or have a pH value higher than the hair's natural value. This causes the cuticle layer to swell, allowing the product to act on the cortex. It is therefore essential to thoroughly rinse the hair following a chemical process and apply a good re-structuring conditioner.
