Processing time is one of the most critical variables in any color service. Too little and the dye doesn't penetrate enough; too much and you over-process, damaging hair and darkening the result.
Permanent color
Permanent color works in two phases: first ammonia opens the cuticle (first 5-10 min), then peroxide oxidizes color precursors inside the cortex (remaining time). Standard time is 30-35 minutes with 20vol. With 10vol you need 35-40 min as the reaction is slower. With 30vol it stays at 30-35 min.
Demi-permanent
Without ammonia, the process is gentler. The color molecule deposits on the outer cuticle without penetrating the cortex. That's why time is shorter: 15-20 minutes. There's no point leaving it longer as the molecule won't penetrate deeper.
Lightener (bleach)
Bleach is the most time-sensitive process. Peroxide breaks down melanin progressively, and the effect slows after the first 30-35 minutes. Never exceed 50 minutes: after that point the oxidant is exhausted and only damages hair without further lifting. Check every 10 minutes.
Toner
Toner deposits pigment without lift. Using low developers (5-10vol), the time is 10-20 minutes. Monitor tone visually and remove when the desired result is achieved, even before the full time, as over-toning is difficult to correct.
Factors that modify processing time
- Low porosity: +5-10 min. Closed cuticle makes penetration difficult.
- High porosity: -5-10 min. Rapid absorption, over-processing risk.
- Heat: -5-10 min. Accelerates the reaction (climazon, thermal cap).
- Virgin vs. treated hair: Virgin hair may need more time on first application.
- Gray percentage: Resistant grays may need 5 extra minutes.