In permanent waving, the size of the curl is determined by the:

In permanent waving, the size of the curl is determined by the size of the rod used during the waving process. The rod acts as a form around which the hair is wrapped, and this determines the diameter of the resulting curl. Smaller rods create tighter curls, while larger rods will produce looser, more relaxed waves. This principle is crucial for stylists to understand as it allows them to achieve the desired texture and volume based on the client's preferences.

The other aspects, such as the amount of solution, the technique applied, and the temperature of the tools, are significant contributors to the overall outcome of the permanent wave, but they do not directly influence the size of the curl. The chemical solution helps to break and reform the hair's bonds, the technique dictates how the hair is wrapped, and the temperature affects the processing time and effectiveness, but the rod's size is the primary factor in determining curl size.