How long to leave hair dye in for grey hair? It depends on the dye you use

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  • If you want to cover your gray hair with a permanent dye, you should leave it in for 45 minutes.
  • Instead, in the case of a demi permanent dye, the exposure time will be 30 minutes.
  • Alternatively, a semi-permanent dye needs to be in for 20 minutes.
  • These are the times to touch up your gray hair or dye it for the first time.


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When do you start timing hair dye?


When your first grays appear, they’re usually a pain   because there’s seems to be only one solution: to cover them up with hair dye.  

If this is the first time you’re dyeing your gray hair, I can imagine you’re full of doubts.

How come?


You go to the supermarket or hairdresser’s store and find several products.

Yes, there are several alternatives to color your hair.

  • Permanent dyes are applied with a 20-volume developer and contain ammonia.   They last three to four weeks on gray hair.  
  • Demi permanent dyes are applied with a 10-volume developer and don’t contain ammonia.   On gray hair they last approximately two to three weeks.  
  • Semi-permanent dyes don’t contain ammonia and aren’t applied with a developer. The   duration of this dye will depend on the washing frequency   because the pigments fade with each wash.


In addition to the difference in components, each product has different exposure times.

The more chemicals the dye contains, the longer you’ll have to leave it in your gray hair.

Why is this?


  If the dye contains ammonia and is applied with a developer, it needs more time to produce the chemical reaction to cover the gray hair.  


That’s why permanent dye is left to act the longest on gray hair.

So, the first thing to do before coloring your gray hair is to decide what type of hair dye to use.

Do you want some advice?


  •   If you have a lot of gray hair  , let’s say 80% or more, I advise you to use a permanent dye. It lasts longer and has 100% gray coverage.
  •   Alternatively, if you have a lot of gray hair and you notice that it’s brittle or frizzy  , I advise you to go for a demi permanent hair product. It also gives you 100% gray coverage and won’t damage your hair as much.
  • If it’s your first time coloring your grays and you don’t have much, you can start covering it with a semi-permanent hair dye. It doesn’t contain ammonia and isn’t applied with a developer. In this way, you’ll be protecting not only your hair but also the gray hair that’s more fragile.


Now that you know which hair dye is best for covering your gray hair, let’s see how long you should leave it in to ensure complete coverage.

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Permanent hair dye should be left on gray hair for a maximum of 45 minutes

hairdresser applied a dye too dark

Did you know that gray hair is hair without melanin?

This is why it doesn’t retain the dye pigments for long. Then, you’ll have to touch up the color more often.


  Permanent hair dye is the most used one worldwide to cover gray hair because it covers it 100% and lasts for approximately three to four weeks.  

Why does it cover gray hair and last longer?


Permanent dye is applied with a 20-volume developer and contains ammonia to color gray hair. However, these benefits don’t come for free.

The developer, which opens the hair cuticles, and the ammonia, which fixes the dye pigments, are chemicals. Therefore, they take away moisture and nutrients from your hair.


That’s why   you need leave permanent hair dye in for a maximum of 45 minutes.  


What do you think would happen to your gray hair if you left the dye in for longer?

  • Do you think the dye will last for months on your gray hair?
  • Do you think you’ll achieve a more intense color?


I’m sorry to disappoint you, but nothing like that will happen.


Instead, if you leave the permanent hair dye on your gray hair for more than 45 minutes, you’ll only weaken it. Your hair is very delicate and dries out easily.

Breakage can occur on weak hair.


Do you want another tip?

  Always read the manufacturer’s instructions.  


While most permanent dyes are left in for 45 minutes, each manufacturer gives different tips for best coloring results.

Finally, whether you want to cover the gray at the roots or throughout your hair, the exposure time will always be the same, i.e. 45 minutes.


The demi permanent dye is left in for a maximum of thirty minutes

Why does it need less time on gray hair than permanent hair dye?


  Because it doesn’t contain ammonia, although it’s applied with a 9 or 10 volume developer.  


The chemical reaction produced by the dye is milder. So, it doesn’t need as much exposure time.

Therefore,   you should leave it in for a maximum of 30 minutes.  


As demi permanent hair dye doesn’t contain ammonia, it lasts less than permanent hair dye.

You’ll need to touch it up if after two to three weeks for gray-free hair.


Semi-permanent hair dye is left on the hair for a maximum of 20 minutes

dye hair at home

Semi-permanent hair dye doesn’t contain ammonia and isn’t applied with a developer. Therefore, semi-permanent hair dye is less damaging to the hair, but it lasts less time.

Why does it last less?


Because it doesn’t penetrate the hair core to change the color of your gray hair. Instead, it deposits on the outside of the gray hair, like a color film.

That color film will gradually fade each time you wash your hair.

How can you extend the duration of the semi-permanent hair dye?


  Reduce the washing frequency   and use sulfate and paraben free products.


It’s easy to apply due to its creamy consistency. Remember that its exposure time isn’t longer than 20 minutes.

I know what you’re thinking.


If the semi-permanent dye isn’t peroxide and ammonia-free, and it’s less damaging to the hair,   why can’t I leave it on longer on my gray hair for more coverage?  


Because it’s not necessary! Twenty minutes is more than enough for the pigmentation to color your gray hair.

  •   If you leave it on for more than twenty minutes  , you’ll only overload your hair with pigmentation. That way, you’ll lose more and more color with each wash.
  •   On the other hand, if you leave it on for less than twenty minutes  , it won’t cover your gray hair.



The exposure times of the dye to cover gray hair depends on the hair dye you use.

Permanent hair dye should be in for forty-five minutes; demi permanent hair dye for thirty minutes, and semi-permanent hair dye for twenty minutes.

Remember to carefully read the instructions of each hair dye to achieve maximum gray hair coverage.

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