If metallic salts are suspected, perform a 1:20 test prior to perm service.

• A. 1:20 test (incompatibility test)
• B. pH test
• C. Strand test
• D. Elasticity test

Answer: (A)

Metallic salts in hair can react violently with perm chemicals, causing excessive heat, fizzing, or uneven processing. To guard against this, you perform an incompatibility test—the 1:20 test—before a perm. This test uses a small amount of solution on a tiny strand in a 1:20 ratio to watch for any adverse reaction. If you see a reaction, such as bubbling or unusual changes, it signals the presence of metallic salts and the service should not proceed as planned. If no reaction occurs, you can safely continue with the perm. This test specifically targets metal-related incompatibilities, unlike a pH check, a strand test, or an elasticity test, which assess different aspects of the hair and processing.