How long to leave black hair dye in? It depends on the dye

colorsilk black hair dye

When we talk about how long you need to leave dye in your hair, it’s important to know what kind of dye you’re using.

  • If you use a permanent black dye, you should leave it in for 30-40 minutes. And soon I’ll tell you when you should leave it in for 30 and when you should leave it in for 40, depending on your hair.
  • If you’re going to use a semi-permanent black dye, you should leave it in for 30 minutes to avoid saturating the color.


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Pros and Cons of Dyeing Your Hair Black (no one tells you about)


Based on the color scale hair colorists use, black is lowest on the scale, assigned the number 1, and lightest blonde is the highest at number 10.

Those numbers aren’t random; they tell us that hair colors are organized from darkest to lightest.

And also tells us the strength of the pigments in dyes for each color.


natural hair colors

 Black hair dyes are made with the strongest, most persistent pigments. 

That’s why there are some pretty popular sayings out there about black hair dye, like:

  • Black dye covers everything.
  • Black hair is the hardest to bleach.
  • You don’t need to bleach your hair if you dye it black.
  • Black dye is easy to maintain.

And each and every one of those things is true. Black dye has gained its fame because of the strength of its pigments.


Because you can use black dye on every hair color: it works just as well on blonde as dark brown hair, and you don’t need to do any chemical processing before using it, like bleaching your hair.


It’s also true that black pigments are the hardest to get rid of in your hair because they are the most persistent.

And it’s a fact that it’s one of the easiest colors to maintain unless your base color is very light.

So, it’s a great choice if you want to go for a color that’s great power is in its pigments. And it’s also really important to keep that power in mind when considering  how long to leave the black dye in your hair. 


Because unlike other dyes, where you should always strictly follow the instructions included for how long to leave them in your hair,  black dye works faster because of how strong the pigments are. 

What do I mean by that?


Let’s say that you bought a black dye from GARNIER, like Blackest Black, which is a deep black.

When you read the instructions included in the box of dye, it probably says to leave it in your hair for 45 minutes.


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And I always recommend following the instructions from the box.

But, black dye might be the exception to that rule.

Because  if you leave it in for 40 minutes instead of 45 minutes, the color would turn out just as intense. 



Because the color molecules in black dye are smaller than the molecules in lighter colors, which means they can penetrate into your hair cuticles easier and faster.


 Of course, you should also follow a minimum amount of time to leave the dye in your hair, which for black dye would be 30 minutes, and it will always be 30 minutes whether you use a permanent or semi-permanent dye. 

So, let’s take a closer look at how long you should leave the black dye in your hair depending on the kind of dye you use.

Tabla de Contenidos


How long to leave permanent dye in your hair

black dye acts faster than blonde

You should leave permanent dye in your hair for a maximum of 45 minutes. That’s the amount of time the dye manufacturers recommend so the chemical reaction can finish without any interruptions and the color turns out even.

But, there’s an exception to every rule.

And that’s why,  when it comes to black dye, you have the option to rinse it out before 45 minutes have fully gone by. 


Because black dye is made up of smaller color molecules than those in blonde dye, for example. And because of that, they penetrate into your hair cuticles quicker, changing your hair color faster.


Because of that,  black dye takes between 30 and 40 minutes to change your hair color. 

Why is there such a difference in the range?


Because every head of hair can react differently when you use the black dye.

And based on my experience as a hair colorist, some hair takes less time to absorb black dye than others. And that happens even when you use the exact same brand of dye.

For example:

  •  If your hair is already dyed , you should leave the black dye in for 40 minutes.
  •  If your hair is bleached , you should leave it in for 30 minutes.
  •  If it’s the first time you’re dyeing your hair with black dye , I’d recommend leaving it in for 30 minutes.


What you should never do is leave the black dye in for more than 45 minutes, which is the maximum amount of time you can leave any permanent dye in your hair.

Because if you do, the chemical reaction that changes the color will hurt your hair, leaving it dry and prone to breaking.


How long to leave semi-permanent black dye in your hair

woman applies black dye to her hair with gloves

If you’ve chosen to dye your hair with a semi-permanent black dye, that means that you don’t want to change your hair structure.

Because semi-permanent dyes don’t modify your hair color, they just deposit in the outermost layer of your hair.

In this case,  it’s super important that you always respect the minimum amount of time to leave the semi-permanent black dye in your hair, which is 20 minutes. 


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If you rinse semi-permanent dye before 20 minutes have gone by, the pigments won’t stick to your hair and the color you end up with will be faded black.

 My professional opinion is to leave the semi-permanent dye in for 30 minutes maximum. 

Because otherwise, it will saturate your hair.

What does that mean?


Color saturation will make your hair stain anything and everything it touches. And, the black dye will fade faster with every wash.


Lastly, I want to clarify something that will help you for either kind of dye – permanent or semi-permanent – and for all colors, from black to blonde.

 You should always count the time for how long you leave the dye in your hair from the moment you finish applying the dye to your hair.  That means that the time doesn’t start from when you began using the dye in your hair.

So, you need to start timing how long you leave the dye in your hair from when you finish applying it to all of your hair.


Black dye is designed with persistent and intense pigments, which is why it takes less time than other colors to change your hair color.

If you want a color that lasts a long time, I’d recommend not rinsing the dye before 30 minutes have gone by or after 45 minutes, because if you overdo it with permanent dye, it will hurt your hair.

And if you leave semi-permanent dye in too long, you’ll end up saturating your hair and the color will last less time.

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