Hair perm waving solutions are either acid or alkaline. Acid: Acid perm solutions have low pH balances, typically between 4.5 and 7. They aren’t as strong as alkaline solutions, making acid ...

Early, haphazard techniques gave way to "cold waves" involving chemicals but no heating and 1970s "acid perms" which were gentler on the hair. The 1980s -- the decade of excess -- saw big ...

There are different perm treatments (acid and alkaline) for different hair textures. “Acid perms usually have a pH rating between 4.5 and 7.0 and require heat. These are [comparatively] less dam ...