Which chemical process requires a specific pH range between 4.5 to 7?

The correct choice is true acid waves, which require a specific pH range between 4.5 to 7 for the chemical process to be effective. This pH range is crucial because it allows for the proper functioning of the ingredients used in true acid waves, particularly the type of acid that facilitates the perming process. In this range, the acid helps to open the hair cuticle slightly, allowing for the penetration of the waving solution while being less damaging than higher pH solutions.

True acid waves typically utilize glycolic acid or other acids to create a curl while also minimizing damage to the hair structure. The specific pH range ensures optimal performance and better results in terms of curl formation and longevity, offering more control over the process compared to other types of waves that may function at higher pH levels.

Other types of waves, such as alkaline waves or cold waves, work best at higher pH levels, which are suitable for different formulations and intended results. Understanding the role of pH in these chemical processes ensures that you can achieve the desired outcome while maintaining hair health.