Which type of perm uses heat to set the curl?

The type of perm that uses heat to set the curl is the thermal perm. This method involves the application of heat to facilitate the curling process, which helps to alter the structure of the hair by breaking down disulfide bonds and allowing them to reshape. Thermal perms generally produce more defined curls compared to other methods and typically offer better longevity in the style created.

In contrast, the cold perm relies solely on a chemical reaction without the application of heat, making it a suitable option for those who want looser, more natural-looking waves. Digital perms utilize a combination of heat and specific digital controls to create soft, flowing waves, but they are distinct from traditional thermal perms in their method and end results. Body wave perms may vary in technique, but they are not specifically focused on heat application as a defining characteristic, thus differing from what is typical of a thermal perm.