What does Foil do When Bleaching Hair (according to a pro hair colorist)

speed up the process

Foil plays an important role in bleaching.

First of all, I want to tell you quickly about bleaching, so you understand the role that foil plays.

  • Bleaching is a chemical process that breaks the cuticles of your hair so that the fibers can expulse their color.
  • This chemical reaction is produced by the mixing of two ingredients: ammonia and peroxide.
  • All chemical reactions produce heat and need a constant temperature to ensure that the process continues.
  • Foil is in charge of maintaining the temperature and producing heat.


 The function of foil is to maintain the temperature during bleaching so that the chemical reaction doesn’t lose heat. 


Now that you know the role that foils plays in bleaching, surely you’ll have some more questions.

I’m going to respond to the most frequently asked questions directed to me by my hair salon clients, so keep reading to learn all you need to know about foil and bleaching.


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Do you always have to use foil when bleaching?

three shades

No, it’s not always used.


  • Foil is normally used when you’re bleaching your hair by more than three shades or doing a technique that requires turning your hair white or a really light tone.

Balayage and highlights in very blonde tones are normally applied with foil—with this, waiting times are shortened given that the foil speeds up bleaching by lending heat to the process.

 Bleaching of less than three shades is done without foil, and there’s no difference in the result. 


  • Foil is the only tool that can accelerate the bleaching process.

Any balayage, highlights, or ombre technique can be done without foil.


  • Another reason that foil is not used is for hair health.

Bleaching is a chemical process that damages hair, and the foil adds a lot of heat.

 For this reason, many times in the salon, stylists don’t bleach with foil if the hair is already damaged. 

Excessive heat can burn hair and even split it.


Your hair, while bleaching with foil, can reach temperatures of 50 degrees Celsius or more.

Imagine the damage that this can cause for dry and brittle hair!


If your hair is damaged, they won’t bleach it with foil, but don’t worry; the results will still be the same, and you’ll look fantastic.

So now you know in which cases the stylist will use foil during bleaching.


Can you bleach hair without foils?

  • Yes, you can bleach without foil.

Bleaching without foil is more common than you’d think.

 For stylists it’s even much simpler to bleach hair without foil than to bleach with foil. 

Can you imagine why?


  • Very simply, it’s because of putting in the foil.

Whenever a client comes to the salon to bleach her hair, and I need to do it with foil, I ask for help from my assistant.

Putting in foil takes a lot of time and is a very long process.


  • The bleaching technique without foil is called freehand.

It’s a simple technique and easy to use.

On the other hand, if you ask yourself how many shades can you lighten your hair without foil?


  • The answer is that you can bleach your hair the same amount of shades, only that instead of taking 20 minutes, the process will take between 30 to 40.

As I told you before, foil only plays the role of accelerating the process by producing heat.

There’s no difference in the results if you apply the foil or not.


What happens if I decide to bleach my hair without foil?

Nothing changes.

If you decided to do it without foil, the only difference is that the process will take more time than it would with the foil.

And that’s because your hair is loose and cools quickly.

To solve this problem, I’m going to give you some tips that will be very useful:

  • Once you’ve applied the bleach mix, move away from any airstreams
  • You can put on a shower cap or nylon bag to maintain the heat
  • You can use a hairdryer at a low heat setting.


If you follow this advice, your bleaching treatment will move forward perfectly, and you won’t cut heat out of the process entirely.


Is there a difference between bleaching with foil and without?

  • If we’re talking about results, no, there’s no difference.

Bleaching is the same with or without foil.

You can always lighten by more than three tones—the foil doesn’t affect this.

Now, if we’re talking about how long bleaching takes, things are different.


  • Foil accelerates the chemical process. As a result, bleaching with foil is much faster.

If you bleach with foil, it will take 10 to 20 minutes to bleach your hair.

Always depending on the tone, you’re hoping to get, you can check the tone every 5 minutes so that you don’t lighten too much. 


  • If you bleach without foil, it will take 20 to 40 minutes to bleach your hair.

This also depends on the tone you’re hoping to get  , but because your hair won’t be covered by foil, you’ll be able to see how the process is going without any problem.e  


  • Whether with or without foil, when you get your desired tone, wash your hair with shampoo and lukewarm, almost cold water. This will stop the chemical process automatically.


Can you use any type of foil, or is there a special kind for hair?

  • The foil is the same that is used for cooking in the kitchen.

You can buy it in any supermarket. It’s sold in rolls of 7 meters.

You can cut strips if you want to bleach sections of your hair at a time.

Or you can apply the bleach mix and then wrap all of your hair in the foil.


  • It’s also sold in salon stores, but it costs much more.

I recommend that you go to the supermarket or some baking supply store that has all the different types of foils and paper.



Whether with or without foils, bleaching is a chemical process, and you should be very careful when applying it to your hair.

You need to be sure of the tone you’re hoping to achieve.

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