An acid perm requires which of the following?

An acid perm requires a plastic cap and a preheated dryer to create the optimal environment for the perming process. Acid perms work at a lower pH compared to alkaline perms, which necessitates the use of heat to activate the waving solution and enhance its effectiveness. The plastic cap helps to retain moisture and heat during the processing time, which is crucial for the acid solution to properly penetrate the hair and shape the curls.

Using a preheated dryer in conjunction with the plastic cap aids in maintaining a consistent temperature necessary for achieving the desired curl formation without excessive damage to the hair. This method emphasizes the balance between the heat application and the gentleness of the acid solution, which is particularly beneficial for hair that is more delicate or previously processed.

Other options, such as a drying hood, cold air setting, or styling mousse, do not align with the specific requirements and techniques used in acid perms, which focus on maintaining the health of the hair while effectively creating curls.