Satin Fern

Hair colour mixing & hair growth calculators

Watch the clock, not your phone

Hair dye processing timer

Separate timers for roots, lengths, toner and gloss, each set to the time on your product's instructions. They count from a fixed finishing time, so they stay right if your phone sleeps or the page reloads.

Sound and alerts are off until you turn them on; your browser asks before it shows alerts.

Add a timer

Minutes (35), minutes and seconds (12:30), or hours (48 h). Up to 8 timers and 72 hours each.

The product's instructions set the time, not this page. The preset times are only starting values: change each one to match your leaflet, never leave colour on longer than it says, and rinse straight away if your scalp burns or itches. Not medical advice.

How to use it

  1. Set each time. Type the processing time from your product's instructions into each timer: plain minutes (35), minutes and seconds (12:30) or hours (48 h). Rename timers to match your steps.
  2. Turn on sound or alerts if you want them. Browsers only allow sound after a tap, so tap Sound on before you start. Alert me asks the browser for permission to show a notification when a timer ends.
  3. Start, pause, add time. Each timer runs on its own. The ring shows the time left; when it reaches zero the card turns red and counts how long it has been over.

Worked example

Your leaflet says 30 minutes on the regrowth, then pull the colour through the lengths for the last 10 minutes. Set Roots to 30 and Lengths to 10, start Roots after applying, and start Lengths when Roots shows 10:00. Both finish together.

The allergy alert test preset runs for 48 hours. Close the tab if you like: come back and it shows how long is left, or that it is time to check the test area.

Why time it at all?

The FDA's advice on hair dye is to follow the directions, never leave the product on longer than they say, and keep track with a clock or timer. Leaving colour on longer does not make it work better; it gives the chemicals more time to irritate the scalp.

Lighteners need watching rather than a fixed time: the lightener check preset is a reminder to look at the lift every 10 minutes, within the maximum time on the packet.

The timers are saved in this browser only, with their finishing times. Phones pause web pages to save battery, so a sound or alert can arrive late or not at all while the page is in the background; the timers themselves stay correct. Keep screen on, where your browser offers it, stops the screen from sleeping while the page is open.

Sources

  • U.S. Food and Drug Administration, Hair Dyes: do not leave the product on longer than the directions say; keep track of time using a clock or timer; do a skin test before every use.
  • NHS, Hair dye reactions: test at least 48 hours before use and do not leave dye on longer than recommended.

Questions

Will the timer keep going if I lock my phone?

The time stays correct, because each timer stores when it will finish rather than counting seconds. What may stop is the sound or alert: phones pause background pages, so check the screen near the end or turn on Keep screen on.

Why is there no sound?

Browsers block sound until you tap something on the page. Tap Sound on: you hear a short chime to confirm it works. After a reload, tap it again.

How long should I leave hair dye on?

Exactly as long as your product's instructions say; times differ between permanent, demi-permanent and high-lift colours, toners and lighteners. Leaving it on longer does not improve the result and can irritate the scalp.

Is anything I enter sent anywhere?

No. Timer names and finishing times are saved only in this browser's local storage so they survive a reload. Back to the four starting timers removes them.