# Which Relaxer Can Swell Hair to Roughly Double Its Diameter?

> The strong alkalis that can swell hair up to twice its normal diameter are hydroxide relaxers. Texas barber exam chemical services answer.

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Last updated: 2026-08-11

**The answer is hydroxide relaxers. They're strong enough to swell the hair shaft to roughly double its normal diameter while processing.**

Thio relaxers work through a different, gentler mechanism and don't cause that same level of swelling. Neutralizers and waving solutions aren't relaxers at all — neutralizers stop chemical action after processing, and waving solutions are for perms, not straightening. That extra swelling with hydroxide products is exactly why timing and strand testing matter so much: push it too far and you're looking at breakage.

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