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How Long to Leave Hair Color In

Quality hair color can transform your look. You’ll feel beautiful and confident when stepping out in a new color, whether you choose to go darker, lighter, or even opt for a contemporary color like blue. Coloring your hair at home means understanding more than just application techniques and knowing how long to leave hair color in. It’s time to talk about color processing time.

How Long to Leave Hair Color In

What Does Color Processing Time Mean?

In general, color processing time is the length of time it takes for a haircolor product to change your natural or current hair color.

Permanent hair color plus developer combine to permanently change the color of your hair. An alkaline agent in the color product works to open your hair’s cuticle layer, which then allows the color and developer to work their way in changing your hair’s natural pigment at its cortex.

The time it takes for the developer to change your natural pigment, developing new color molecules within the cortex is considered the color processing time.

How Long to Leave Hair Color In

Color Processing Time 101

On average, processing time for any standard hair color application is approximately 30 minutes. If you’re attempting maximum gray coverage or using a high-lift coloring product, the standard processing time typically clocks in at 45-minutes.


The first 15 minutes of processing are the time needed for the agents to open the hair’s cuticle, penetrating to its cortex. The second half of the processing time allows for the maximum deposit  of color and for any remaining lightening that’s needed.


Pro Tip: Perform a strand test before coloring your whole head. Do this about 48-hours before processing your new color. A strand test offers two benefits: you’ll discover if you have any sensitivities or allergies to the product and it will help you determine the time needed for processing in order to reach your desired color.


How Long to Leave Hair Color In

Roots First

It’s often recommended to apply the color to your roots first, allowing it to sit on the roots for about 10 minutes before applying the rest of the color. This technique becomes especially important when your roots or growth are significantly darker than the rest of your hair. Just need a root touch-up? Check out our best tips for easy, fabulous root touch-ups.

How Long to Leave Hair Color In

What If I Lose Track of the Processing Time?


You did your strand test and determined that 35 minutes was the perfect processing time to achieve your desired color. At the 25-minute mark, your phone rings. At the 50-minute mark you’ve just hung up the phone and realize how long your color has been processing. Now what?


First, don’t panic. Most coloring products “shut off” after a certain period of time so if your strand test said 35-minutes but you left it on for 50-minutes, it’s likely to be just fine. However, when using any type of highlighting process or lightening that contains bleach — keep track of your time. These products typically don’t “shut  off” and extending the processing time too long can result in a shade you don’t want plus it can damage your hair.

How Long to Leave Hair Color In

What Affects Processing Time?


We already know that it can take longer to process color at the roots when they are two to three shades darker than the rest of your hair. Hair density also can affect processing time. If your hair is dense, it may process faster closest to the scalp but take longer towards the tips. To compensate for the difference in time due to hair density, apply the color to roots (hair closest to the scalp) first and allow it to set for 10 minutes before coloring the rest.

Coarse hair or hair that’s over-processed (frequently colored and/or damaged) often takes longer to color process, which means a strand test is an important step not to skip. A strand test on your coarse hair will let you know how much longer than average you should allow the color to process.

Length of hair often affects the processing time, especially when applying an all-over color. Typically the ends of your long hair are more porous than the hair nearest to the scalp. This means the ends take less time to process because they absorb the color more quickly. However, depending on the texture and thickness of your hair, the roots and growth near the scalp may need a longer processing time as well. Again, it’s recommended to perform a strand test (or two) to best determine the processing time for your hair type.

Pro tip

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