How long do I leave 40% developer in my hair?

Author: Prof. Delfina Berge  |  Last update: Friday, September 12, 2025

40-volume developer should not be left on your hair for more than 30 minutes. Generally, a processing time of 10–20 minutes is enough to achieve a lift without causing excessive damage. Check the hair frequently to monitor the color lift, and rinse thoroughly when the desired shade is achieved.

Will a 40 volume developer lighten hair by itself?

Developer alone won't lighten your hair significantly. Developer (which is usually hydrogen peroxide) works by opening the hair cuticle to allow lightening agents to work. By itself, it won't remove pigment from your hair.

Is a 40 volume developer too strong?

Strength of Developer: A 40-volume developer contains 12% peroxide, which is very strong and can lift hair color significantly. However, using such a strong developer can also cause damage to the hair.

How long does a 40 volume developer last?

Peroxides or Developers don't 'spoil' or go bad but they can deteriorate meaning the Hydrogen Peroxide breaks down to free oxygen and water causing the product to weaken (go from 10 Vol. to 9 Vol. or less) or it can dehydrate or lose water and get more 'concentrated' (go from 20 Vol. to 22 vol. or more) However, all ...

How many levels does 40 vol lift?

40 Volume (12%) Developer

A Volume 40 developer is only used for lightening and can lift up to 8 levels. It is recommended for use with a lightening cream or powder for those who want to achieve blonde results.

How long should I leave 40 volume developer on my hair to lighten it?

How long to leave 40% developer in hair?

40-volume developer should not be left on your hair for more than 30 minutes. Generally, a processing time of 10–20 minutes is enough to achieve a lift without causing excessive damage. Check the hair frequently to monitor the color lift, and rinse thoroughly when the desired shade is achieved.

When should I use a 40 volume developer?

If you're looking to lighten your hair by three or more levels, 40 volume developer is the option for you. It's also a good choice if you have very resistant hair that's difficult to color. People choose 40 volume because it's strong enough to lighten even the darkest hair.

How long should I leave 30% developer in my hair?

One of the most common questions is: How long to leave 30 volume developer on hair? In general, it's recommended to leave it on for 15–30 minutes, depending on how much lift you're looking for. However, going over this time can cause significant damage.

What happens if you use more hair color than developer?

Using more hair color than developer can lead to uneven color results and insufficient coverage. The developer is crucial for opening the hair cuticle and allowing the color to penetrate, so an incorrect ratio can compromise the effectiveness of the dye.

What level developer is in Box dye?

The developer found in box color ranges between 20 and 40 volume because that is what is needed to cover gray or to change a very dark shade. Frequently coating the hair shaft with a high volume developer will cause damage, particularly if the starting condition is weakened or fragile.

What happens if I use 40 developer instead of 30?

Developer choice going lighter with regular color

Use 20 Vol if you are aiming for a 1-2 level lift (and if you have grey hair that needs covering). Use 30 Vol if you are aiming for a 2-3 level lift. Use 40 Vol if you are aiming for a 3 level lift and if the hair is particularly difficult to color.

How many sessions to go from dark brown to blonde?

From a strand test, you should also get a better sense of how many sessions you'll need to make the full transition. For example, going from dark brown to light blonde hair may require three to four sessions.

How do you make 40 volume developer into 20?

Mixed equal parts distilled water with 40 volume to make 20 volume. 1 oz distilled water and 1 oz 40 volume developer will give you 2 oz of 20 volume developer.

What does 40 developer do to dark hair?

Highlighting and Balayage: For creating highlights or balayage on dark hair, 40 volume developer is often used to achieve the lighter tones necessary for these techniques. It allows the color to lift to the desired level, especially when working with dark or resistant hair.

Will 40 volume damage my hair?

40-volume developers contain 12% hydrogen peroxide. These lift your hair up at least 8 levels! This developer is not appropriate for at-home use at all, unless you are a hair coloring professional, because this developer can cause serious damage to your scalp and your hair.

How to lighten dark hair to light brown?

Use Hair Lightener or Toner

Hair lighteners or toners are great for lifting darker shades and achieving a lighter shade. Apply the toner or hair lightener to your hair according to the product's instructions. Rinse it out once you've reached your desired color.

What happens if you put grey hair dye on brown hair?

If your hair is brown, you may need to bleach it more than once before you apply the grey dye. It's important you get your hair as light as possible before you attempt to turn it grey – this will help ensure a more even tone and vibrant, all-over colour.

How do I know if I put too much developer?

Too much developer added to a hair color formula will dilute the artificial dye molecules, and add too much oxygen to the formula. This will typically display a sheer end result that does not have the depth you may have anticipated.

What happens if you mix semi-permanent hair color with developer?

By adding developer to your semi-permanent hair color, you can expect the following benefits: Enhanced Vibrancy: As mentioned before, the addition of developer helps the color molecules penetrate deeper into the hair shaft, resulting in a more vibrant and intense color.

Should I rinse bleach out of hair with cold or hot water?

Step 7: Wash it

Use lukewarm water, too hot or cold of water can shock your hair in its already fragile state. Make sure to completely rinse out the bleach and gently wash your hair to get out all the product.

Will 40 developer lighten hair without bleach?

You cannot lighten your hair without bleach. 40 volumn applied to the hair shaft will open it up and prepare your hair to receive the color. But to lighten your hair correctly you will need bleach.

What happens if you leave developer in too long?

And remember, timing is everything - leaving the developer on for too long can lead to over-processing, while not leaving it on long enough can result in poor color results.

How long can you leave 40% developer on hair?

40 volume bleach is very potent and isn't supposed to be left in your hair for more than 10-20 minutes. If you have coarse or very dark hair, you can leave it a few minutes longer.

What developer to use to cover grey hair?

The standard developer for gray coverage is 20 Volume; however, 30 Volume and 40 Volume can also be used if the percentage of gray is low and additional lift is needed to achieve the desired result.

How to dilute 40 volume developer to 30?

1 part 40 volume, 3 parts water =10 volume. Equal parts 40 volume and water = 20 volume. 3 parts 40 volume and 1 part water =30 volume.

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