What does developer do to your hair?

what does hair developer do

I’m sure you’ve been there, in the salon chair with your stylist and she’s telling you about what kind of developer she’s using. You’re like “huh?” Well, we’re here to explain it all. What does developer do to your hair? Read on!

Developer is a chemical that lifts the natural color out of hair and lightens it up to a level 10-12 shades lighter than its original color. But can developer damage your hair? What do the different volume levels mean? And which one do you need?

We’re here to answer all of these questions, so you can make the right decision for you. Let’s go!

What is hair developer?

In the hair industry, a developer is an agent that alters the color of hair by removing or changing its pigment.

It’s used to lighten hair, remove unwanted tones and create different colors.

Developers can be found in many forms: as a lotion, cream rinse or powder that you mix into your shampoo and conditioner.

A developer is made up of hydrogen peroxide and comes in several strengths. The lowest for hair coloring is 10%, 20%, 30%,40% and even 50%.

Developer works by breaking down the hair shaft and opening it up. After the hair is open, it can receive the hair color or bleach.

The color will fill the hair and bleach removes color from the hair. If you apply color without a developer, it won’t be able to penetrate and stay inside the hair shaft. The most it will do is stain the hair.

Developer is mixed with colour and hair dye pigment to deposit the colour onto your hair. It ‘develops’ the dye – that’s why they call it developer!

How to choose the right hair developer for you.

  • Volume 10 developer will lift your color a single level.
  • Volume 20 developer will change your hair color by 1 or 2 shades.
  • Volume 30 developer to lift your hair color by 3 or 4 shades.
  • Volume 40 is super strong and not for home use!

How does hair developer work?

What does volume 10 developer do to your hair?

10 volume can be used with permanent color hair dyes for depositing color, but it will not offer much grey coverage or lift.

However, volume 10 is the default developer many hair toners and glazes.

When mixed with bleach, volume 10 can give you 1-4 levels of lift may result depending on how you apply your hair bleach.

It’s the most used developer for more subtle hair colour changes like from dark brown to light brown, red to strawberry blonde and even caramel to honey blonde.

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What does 20 developer do to hair?

20 volume developer is the most popular choice for permanent hair color. It can give up 1-2 levels of lift on finer hair.

It’s also a good option for grey hair coverage. However, some hair types resist this product better than others! If you have a lot of stubborn greys, you likely need something stronger.

Volume 20 is probably the most common developer used in salons. It’s no good for hair toners and glazes though.

When used with bleach, it’s pretty powerful and can lift your hair up to 9 levels. It’s good for going from dark brown to light brown, adding highlights and balayage colours, and lifting unwanted colours.

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What does 30 hair developer do?

30 volume developer is getting into the strong stuff. This isn’t the developer you use to deposit colour into your hair as it will fry it for no reason.

Volume 30 is good for bleaching dark hair. 30 volume and higher developer can react really strongly to heat. So you need to be careful with processing treatments like foil highlights to avoid damaging your hair.

It’s also a good developer to use for stubborn grey hair, depending on the texture and health of your hair.

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What does 40 volume developer do?

40 volume is reserved for the kind of very thick and dark hair like black that needs a higher intensity strength.

If you try to use it on hair that is medium to fine thickness all you will do is overprocess and burn the hair. 

40 Volume is pretty serious stuff. It’s extremely harsh on the hair and the reason why you have to leave it on for less time than other developers.

It strips the hair of colour and can also remove all the moisture in your hair. It can be used to get a great base for super icy-shite blondes like platinum.

It is a good strength to use for techniques like balayage and ombre where it isn’t close to your scalp or all over your hair.

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What happens if you just put developer in your hair?

Developer is made of varying strengths of hydrogen peroxide which are hair lightening chemicals.

So in theory, it can be used to lighten your hair on its own. But we wouldn’t recommend this!

That doesn’t mean that it SHOULD be used to lighten your hair. It will require heat and has to stay wet in the hair for quite a while for there to be much effect, and the resulting color will be brassy and your will probably end up feeling like straw.

So while it’s less damaging than colouring due to the lack of ammonia, it still impacts your hair integrity for a result that is very brassy and ick.

Hair color is all about mixing the chemicals to the perfect ratio. You need to activate the developer with color – lighter color, darker color or bleach – otherwise the effort is not worth the results.

Hair developer TOP TIPS

The higher the volume, the stronger the chemicals and the more the developer will lift your hair.

Don’t use a stronger volume than you need as it will damage your hair for no reason!

Mix developer with Olaplex to strengthen your hair bonds and prevent any breakage or damage.

Is developer bad for hair?

Think of the volume of your developer as the amount of lift or lightening you want to achieve.

Using too high of a volume developer can result in unnecessary lightening and major damage to the hair. Too low a volume, and you may not get as light as you want.

Developer over 30 volume can be too strong and cause burns if it touches your scalp. 30 volume developers and above are typically used on dark hair, while lower volumes of developer, such as 10 and 20, are used for naturally lighter hair.

Like any hair colouring product, hair developer can damage your hair if not used carefully. Always make sure your hair condition is up for having chemicals applied to it. And give your hair lots of TLC before, during and after bleaching or colouring.


We hope this article has helped you to better understand what developers do for your hair.

Whether you’re thinking of going from really dark to really light, ombre, balayage, or just adding some highlights and texture, we hope you now know how to find the right level for you. Good luck!