How long should sodium hydroxide be left on hair during processing?

Sodium hydroxide is a powerful alkaline chemical commonly used in chemical relaxers for hair. The recommended processing time for sodium hydroxide varies based on the hair's condition, texture, and the specific formulation of the product used. It is crucial to follow manufacturer guidelines to prevent potential damage to the hair or scalp.

The choice indicating that sodium hydroxide should not be left on for longer than 40% of the recommended processing time reflects a safety practice that helps reduce the risk of over-processing. Over-processing can lead to excessive dryness, breakage, and scalp irritation. This guideline ensures that the treatment is effective while minimizing the potential for damage to the hair structure or scalp health.

By sticking to a specified percentage of the overall processing time, hairstylists can maintain better control over the treatment process and achieve desired results safely, making this choice the most appropriate in the context of hair care and chemical treatments.