Which perms cause minimal swelling; therefore hair must be wrapped with firm, even tension?

• A. Acid perms
• B. Alkaline perms
• C. Exothermic perms
• D. Low/no Thio perms

Answer: (A)

Swelling during processing is shaped by the solution’s pH: milder, acidic perms swell less than alkaline ones. When swelling is minimal, you can apply firm, even tension while wrapping because the hair isn’t expanding much, so you get a smooth, uniform wrap and curl. Acid perms are designed to be gentler with less swelling, making them the best fit for using stronger, consistent tension. Alkaline and heat-activated perms tend to swell more, which often requires looser or adjusted tension, and other formulas like low/no thio vary in milder behavior but aren’t defined by minimal swelling like acid perms.