A chemical based permanent hair wave product. Acid perms generally have a pH that ranges from 6.5 to 8.0. Acid waves are considered to be milder curl inducing products than Alkaline products. Acid waves are designed to create a soft, loose, natural looking curl.
Acid are used in hair perm products to stabilize formulas that have an unwanted alkaline level. Its purpose is to lower the pH level of a substance.
Although it is believed that acid perms are less damaging, this may not necessarily be true due to a variety of factors. Whether an acid formulation is appropriate or not needs to be evaluated on a case by case basis. Some cosmetologists believe that acid perms can be applied on top of previously colored strands. Again, this may or may not be true depending on the porosity of the hair.
Regardless, a patch test must be performed on all hair before a full perm application is applied to gauge possible results and guard against unwanted damaged.
Acid perms may also be referred to as acid texturizing or acid permanents.