True acid waves have a pH balance between:

True acid waves are a type of perm that are designed to create curls or waves in the hair by utilizing a lower pH than traditional alkaline perms. The critical aspect of true acid waves is their ability to work effectively at a pH range of 4.5 to 7. This lower acid pH is suitable for chemically processing hair while being gentler on the hair structure, resulting in less damage and more control over the perming process.

At this pH level, the acid waves can penetrate the hair shaft in a controlled manner, allowing for effective curl formation without overly swelling the hair cuticle, which can often lead to frizz or damage. Furthermore, the use of true acid waves allows for better adherence to the hair’s natural state, providing a softer texture and more natural look to the curls.

The other options present pH ranges that either fall outside of the effective pH range for true acid waves or are not characteristic of their formulation. Understanding these specific pH characteristics is crucial for barbers and stylists as they select the appropriate products for their clients' hair types and desired outcomes.