Final answer:
The most commonly used base control during a perm service is alkaline, which breaks the disulfide bonds in the hair to create a long-lasting curl.
Step-by-step explanation:
The most commonly used base control during a perm service is alkaline.
Alkaline perm solutions typically contain ammonium thioglycolate as the reducing agent. This chemical breaks the disulfide bonds in the hair, allowing it to be reshaped into the desired curl pattern. Alkaline perm solutions have a higher pH and provide a stronger and more long-lasting curl.
Other types of perm solutions, such as acidic or neutral, can also be used but are less commonly used than alkaline solutions.