Following the manufacturer's processing time during a chemical service is important because:

Following the manufacturer's specified processing time during a chemical service (perm, relaxer, or color) is important because leaving the product on too long (over-processing) can severely damage or break the hair, while removing it too soon (under-processing) gives weak or incomplete results. Timing, along with strand testing and monitoring, keeps the service safe and effective. 'Longer is better' is a dangerous misconception with strong chemicals. Respecting processing times is a key safety-and-results principle emphasized throughout the chemical-service content.