Final answer:
A common reducing agent found in the salon is ammonium thioglycolate, which is used in the permanent wave process to shape the hair by reducing and rupturing disulfide bonds.
Step-by-step explanation:
A common reducing agent found in the salon is ammonium thioglycolate. In the permanent wave process, ammonium thioglycolate is used to reduce and rupture some of the disulfide cross-links in the hair, allowing for the shaping of the hair. This compound is capable of donating electrons, making it a reducing agent.