California Cosmetology Practice Exam

Which chemical is commonly used to relax curly hair?

1. Calcium hydroxide

2. Sodium hydroxide

3. Potassium hydroxide

4. Ammonium thioglycolate

The correct answer is: Sodium hydroxide

The use of sodium hydroxide for relaxing curly hair is well-established in the beauty industry. This chemical is known as a "lye relaxer" and operates by breaking the disulfide bonds in the hair's protein structure, allowing the hair to become straighter. Sodium hydroxide is particularly effective for coarse and resistant hair types, as it provides a strong enough formula to achieve significant straightening results. When discussing other chemicals, while calcium hydroxide and potassium hydroxide are also used in relaxers, they are typically considered milder compared to sodium hydroxide. Calcium hydroxide is often combined with another agent to create a non-lye relaxer. Potassium hydroxide is also present in some relaxers but again tends to be less common for those seeking strong results on tightly coiled hair. Ammonium thioglycolate, on the other hand, is primarily known for use in perming, as it can soften and reshape the hair without the same level of harshness associated with sodium hydroxide. It is effective for loosening curls but does not provide the strong, prolonged straightening that sodium hydroxide can achieve. Thus, sodium hydroxide stands out as the go-to chemical for relaxing curly hair, particularly due to its potency