Final answer:
A neutralizer, often a dilute solution of hydrogen peroxide, is used to reharden hair into its new, straighter shape following the use of a sodium hydroxide-based relaxer.
Step-by-step explanation:
When using a sodium hydroxide-based relaxer, a neutralizer is used to reharden the hair into its new, straighter shape. This is because the chemical relaxer process involves breaking down the hair's natural disulfide bonds, which give hair its shape. After the hair is straightened and set in the desired form, the neutralizer, which is an oxidizing agent (usually a dilute solution of hydrogen peroxide), is applied to reform these disulfide bonds in their new positions, effectively setting the hair's new structure.
When using a sodium hydroxide-based relaxer, a neutralizer is used to reharden the hair into its new, straighter shape.
The relaxer breaks the disulfide bonds of the hair, allowing it to be reshaped. The neutralizer, which is an oxidizing agent like hydrogen peroxide, reforms the disulfide bonds in their new positions to maintain the straightened shape of the hair.