Venus Beauty Salon
Forty-eight hours is the number on both sides of a colour appointment: the patch test before it, and the window after it that decides how long the work lasts.
The 48-hour clock starts before the appointment. A PPD patch test has to sit on the skin for 48 hours before any colour, and a reaction can keep developing for up to 72 hours after it appears — so the test area deserves a glance for a day or so even after you have been coloured.
The biggest aftercare threat to a keratin or smooth finish is the wash. Sulfate shampoo strips the treatment in about three washes at 12-15 °C water temperature. A finish that should hold a blow-dry for 3-4 months can be undone in a single week if the wrong bottle is in the shower.
On narrow screens, swipe or scroll the plate sideways.
Colour has its own slow leak. Roots on a previously lightened base take colour faster and fade sooner than virgin hair, so the lighter parts of a head are the first to want refreshing — expect them at the 4-week end of the 4-8 week rebooking window, not the 8-week end.
The strand-test logic applies at home too: hair behaves unevenly from root to ends because it lifts unevenly from root to ends. The freshly coloured lengths near the scalp and the older ends are not the same material, and they will not hold the same shade for the same number of weeks.
If the patch-test area reddens, swells or itches within its 72-hour watch window, raise it with the salon that ran the test before any further colour. For the timings of the services themselves, see How Long Each Salon Service Takes; for the rebooking intervals, see How Often to Come Back for Root, Trim and Perm.
Further reading