How long should you leave 40 volume bleach in your hair?

correct ratio

  • You should leave 40 volume developer in your hair for a maximum of 20 minutes.
  • If you leave it in for longer, your hair could be irreparably damaged. Your hair would run the risk of drying out, becoming brittle, and even breaking.
  • I would advise that if you have no experience with dying, you don’t use 40 volume developer. It would be better to use 30 volume.
  • If you’re still determined to use it, make sure you take all possible precautions so that your hair can withstand the treatment. For example, you can apply coconut oil three hours before you bleach your hair.


Another very important detail.

Before using 40 volume developer, you should evaluate the state of your hair.

  • If your hair is dry
  • If it’s difficult to detangle
  • If you have a lot of frizz and can’t style it


But before you start, let me ask you: why do you want to use 40 volume developer?


40 volume developer is only used in special treatments in the beauty salon.

If you don’t have experience with bleaching, I would recommend that you don’t use 40 volume developer.

 If you want to bleach your hair, I recommend that you do it with 30 volume bleach, which is less harmful to your hair fiber 


Maybe you’ve been thinking that the more volumes the developer have, the more shades you can lighten your hair by at once.

This is true, but also the more volumes, the more damage.


If you want to bleach your hair without damaging it and lighten it easily, keep reading, because, in this article, I’ll let you know all the secrets of the trade.


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Why is it inadvisable to use 40 volume bleach if you don’t have experience with dying?

damaged lengths and ends

Perhaps it may seem a bit repetitive if I mention the damage that 40 volume bleach can cause again.

So I’m going to tell you a story that will take away any doubt you might have about why you shouldn’t use it without experience.


I was in the salon when Vanina arrived, a client that was transitioning to a platinum blonde.

Vanina had moderately healthy hair and had already done two bleaching sessions to be able to take out the dark brown color of her hair.

When she arrived at the salon, her hair was a disaster.


Her roots and new growth were almost white and the rest of her hair blonde, but it was impossible to brush.

I asked Vanina what had happened, and she told me that she had bleached her hair with 40 volume developer.


 The problem was that, while the bleach was in her hair she decided to pass the time by starting an episode of her favorite show on Netflix. When she remembered, it had already been 40 minutes! 

She rinsed her hair quickly, but it was already too late.


I couldn’t detangle her hair because it was like a bird’s nest.

I had to tell Vanina that the damage was irreparable.

The only option was to cut her hair short because the fibers were completely damaged.

While her hair had been bleached lighter, it was completely ruined.

Now, do you see why?


 Developers of 40, 50 and 60 volumes are used in beauty salons for special treatments done by colorists with years of experience. 

You can imagine that it would be much easier for professionals to apply 40 volume developer than to do several bleaching treatments.

The reason they do several sessions is so your hair doesn’t become damaged.

If you apply 40 volume developer, you could lighten your hair by 4 to 5 shades in just one go, but then your hair would take 5 months to recover from the damage.

Or you would even maybe have to cut it.


Vanina wanted to speed up the process and become a platinum blonde faster.

Even if she did manage to become blonder, she lost a lot of hair because I had to cut it to shoulder length.


 Developers of 20, 30, or 40 volumes all have the same function: to open the cuticles of your hair fibers so that they lose their color. 

So now you know that you have to be very careful if you’re planning on using 40 volume developer.


In what scenarios should you use 40 volume developer?

40 volume developer is used to take out very dark tones, like black or dark brown.

In the beauty salon, colorists apply it in the shampoo bowl and massage your hair every 5 minutes.


 The colorist constantly checks how the bleaching is going and if the hair is being damaged. 

But of course, you’ll be asking, why can’t I do it at home?


Let’s go back to Vanina’s situation—she applied 40 volume developer at home.

The mistake that Vanina made was to leave it in for longer than she should have.

While she managed to lighten her tone, her hair suffered irreparable damage.

Do you know how much time you should leave the developer in?


The instructions indicate no more than 20 minutes.

You can take it out earlier. The best thing to do is to check your hair every 5 minutes.


 But you shouldn’t go by the color of your hair for knowing when to wash out the developer. 

Maybe you think that if you left it in for 30 minutes your hair would be lighter.

It doesn’t work that way.


After 20 minutes, the chemical process halts, and this is when the problems begin.

Upon opening the cuticles of your hair fibers, they lose moisture and start to absorb the bleach mix.

Now, do you understand why it’s so damaging to your hair?


Instead of absorbing nutrients, your hair takes in chemicals, like peroxide and ammonia.

For this reason, your hair breaks.

So if you’re hoping to go from dark hair to light in just one day, prepare to sacrifice your hair health.


Which developer should you apply to your hair to avoid damage?

It’s best to use 20 or 30 volume developer.

  • 20 volume developer is for light tones going to even lighter ones: you can lighten by one to two shades.
  • 30 volume developer is for dark tones to light ones: you can lighten by two to three shades.


If you want to get rid of dark shades, like black or dark brown, you should have two bleaching treatments using 30 volume developer.

In this way, you can lighten your hair without extremely damaging it.


But if you still want to use 40 volume developer, I’ll leave you with some advice so that your hair doesn’t suffer as much:

  • Apply coconut oil 3 hours before you bleach your hair. You can also use argan oil.
  • When you make the bleach mix with the 40 volume developer and powder, add some coconut oil to minimize the damage. 8 to 10 drops will do it.
  • Don’t use a cap or aluminum foil, given that these will generate more heat and therefore logically, more damage,
  • Prepare a little bit of the mix and apply it to a small section of your hair, so that you can know what shade your hair will be and if it can withstand the treatment.
  • After the bleaching session, hydrate your hair with a keratin mask.


If you follow this advice, your hair will not be as damaged in the process.

This advice can also be used if you decide to make the mix with 20 or 30 volume developer.



Even if 40 volume developer is very useful, it can greatly damage your hair.

Do you know how Vanina’s story ended?


After 4 months of deep hair repair and several cuts, she finally got her healthy platinum blonde hair.

Keep in mind that it’s better to wait to get that tone you want rather than risk losing your hair or damaging it.

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