You may have heard gray strands take longer to absorb hair dye. But how long do you really need to leave color on to cover grays?
The processing time can vary quite a bit depending on the percentage of grays you have and your desired shade.
In general, gray hair tends to be coarse and stubborn, so leaving color on a bit longer allows the cuticle time to open so pigment can fully deposit inside the strand.
This article will provide some tips and guidelines for leaving hair color on for the right amount of time to cover gray hair and roots.
How Long to Leave Hair Dye in for Gray Hair
How long you need to leave hair dye in for gray hair will depend on the dye you’re using. Permanent hair color needs a full 45 minutes; after that the color is not effective. Semi-permanent and demi-permanent processing time is 20 minutes, maybe 25, but never up to 2 hours; that two hours may be confused with henna.
Permanent Dye
Permanent hair dye is usually ammonia-based and needs a full 45 minutes; after that the color is not effective. This dyeing technique will maintain your hair’s color the longest, but it does have some side effects.
If your hair isn’t adequately nourished before undergoing coloring, it can dry out your hair and leave it looking dull and brittle. Also, always pay attention to your dye-specific instructions.
Semi-permanent
Semi-permanent hair dye won’t stay as long in your hair because it doesn’t have the ammonia to assist with the process. Instead of penetrating your hair, it sits on the shaft and deposits color.
Using semipermanent dyes to cover gray is a fantastic option. Just keep in mind that on highly resistant hair, these gentle formulas will usually just “blend” the grays to look like highlights rather than providing solid, opaque coverage.
Semi-permanent dyes are gentle, and the processing time is 20 minutes, maybe 25, but never up to 2 hours. That two-hour figure may be confused with henna.
Demi-Permanent
A demi-permanent hair dye doesn’t contain ammonia but does use a developer to help the color deposit into your hair. The process won’t be as harsh as a permanent dye, but it’s not as gentle as a semi-permanent option.
To get the best results on stubborn grays, give it 20 minutes, maybe 25, always inside your box’s own maximum, then wash it out immediately. Leaving demi-permanent dye on too long will not only dry out your hair, but the color is “progressive,” meaning it will continue to darken and leave you with a shade much darker than you intended!
How Long to Leave Hair Dye on Gray Roots
Natural gray hair roots are notoriously tricky when it comes to coloring.
If you’re touching up the dye, start with your roots and give them a 20-minute head start before you apply the dye to the rest of your hair; for gray coverage, 45 minutes is recommended every application.
If you’re doing a full-color transformation, leave the dye on your roots for 10 minutes before working with your ends.
Pay Attention to Resistant Patches
If you notice more gray in certain areas, you may also find it harder to get the dye to stick in those spots.
One way to prevent this is to apply the dye to the resistant patches first. This method gives the color extra time to penetrate the hair.
When using this method, be careful to avoid an uneven dye job by thoroughly coating all the hair you want to color. Alternatively, a professional stylist can help you achieve a natural, full-bodied color.
