How long does hair bleach stay active according to a pro hairdresser?

  • Bleach stays active from the moment you finish preparing it until 60 minutes later, one hour.
  • Afterward, it’ll not only lose bleaching power, but it could also severely damage your hair.
  • So, any remaining bleach should be discarded.


to apply to her roots

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That’s how assertive I got up today. Well, actually, I didn’t, but a Whatsapp message a client sent me a few hours ago put me on the alert. When that happens, heavens tremble.

Do you know what she told me? She begged me for help because her hair was completely ruined. Why?


Because she had applied bleach to her hair, but she had prepared it three hours before. The result was burnt hair.

Luckily, she had only applied the bleaching mixture to the mids and ends. So, the solution was simple.

We only had to trim the burned part, which was about ten centimeters long. Yes, she got off lightly. Then, I realized that many people could make the same mistake.


 Preparing bleach and using it 2 or 3 hours later is a giant mistake.  Why?

Girls, wake up. We’re talking about chemicals, super corrosive chemicals for hair.


Also, we mix them up. And when you do, you want to get a chemical reaction in your hair. To ensure that the chemical reaction is not harmful to your hair fiber, you have to use the bleach mixture properly.

You don’t want to damage your hair by managing incorrect timings.

What are those times?


 Once you’ve prepared the bleach, you should use it immediately on your hair as it’ll only work for sixty minutes. Not one more minute, nor two or three.  And the leftover bleach? Straight to the trash!

Do you want more clarity?


Keep reading, because I’ll tell you:

  • How long does bleach last
  • How to bleach your hair immediately after preparing the bleach

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How long does bleach last?

dark and medium hair

I want to be very clear on this point: the bleaching mixture stays active for 60 minutes. 


Once the bleach is applied to your hair, it has two stages:

  • The primary and most lightening reaction lasts 20 minutes.
  • The secondary reaction lasts 40 minutes


During the first 20 minutes, your hair will be bleached very powerfully. Then, it’ll continue to lighten in a sustained way.

For example:

  • If you want to bleach your light brown 5 hair, when you apply the mixture for the first 20 minutes, your hair will lighten 2 levels. After that primary reaction and for the next 40, minutes the mixture will lighten ½ shade.


What do you think will happen if you apply the bleach one hour after preparing it?

The first bleaching chemical reaction will have finished. You’ll only achieve damage to your hair by applying the residues of the chemicals involved.


So, after sixty minutes of mixing the peroxide and bleach, the mixture only damages the hair.  Repeat after me: after sixty minutes of mixing the bleach and peroxide, the mixture only damages the hair. 

It can even burn your skin.

And, of course, any leftover bleach mixture should be discarded.


How to bleach your hair immediately after preparing the bleach mixture

with gloves

Want some advice on how to get the most out of your bleach while it stays active?


Get organized!

The first thing is to have all the ingredients at hand:


Look for a moment without distractions or have to start checking time and color. You must not be distracted.

Are you ready?


Let’s bleach your hair.

  • Comb your hair with a middle part to see your roots and separate it into 4 sections, from ear to ear and from front to back.
  • In a plastic container, mix the bleaching powder with the 30-volume developer until a homogeneous and lump-free mixture is achieved. You can add 10 or 15 drops of coconut oil to minimize damage to your hair fiber.
  • Release one section of your hair. Start applying the mixture from root to tip with a dye brush. Repeat on each section.
  • When you’ve finished applying the bleach mixture, cover your hair with a cap and leave it in for 20-30 minutes according to the shade you’re looking for.


Hey! Don’t play dumb.  Now it’s time to throw out your leftover mix. Don’t feel sorry about it.  


After the exposure time, rinse the bleach mixture with plenty of warm water and wash your hair with shampoo and conditioner.

You’re all set! Mission accomplished and no dangerous traces of bleach around.



Bleach only stays active for 60 minutes after preparation. You should not use it afterward because it’ll only damage your hair fiber.

You should definitely throw away the leftover bleach.

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