How to Use a Soap Cap (Bleach Bath) for Color Correction & Lightening Hair

by Laura Collins1 July 2025Categories: Hair Color 0 Comment

Soap caps are one of the most useful techniques for corrective hair coloring services. They’re easy to apply, process quickly, and are minimally damaging. Throughout this post, I’ll explain what a soap cap is, all of its uses, as well as how to easily perform them yourself from home.

Since I went to cosmetology school all the way back in 2007, “soap cap” is the technical term that I personally use. However, I know that newer beauty bloggers and influencers use other terms for the same technique (this seems to be a big Gen Z trend :)). So throughout this post, I’ll use the terms “soap cap”, “bleach bath”, “bleach wash”, and “shampoo cap” interchangeably. They all refer to the same technique.

What is a soap cap?

You may have heard that “color doesn’t lift color” before. This means hair that has been previously colored with permanent hair dye will not be able to go any lighter with hair color. This is because the permanent color molecules are now locked into the cortex of the hair, permanently. And if you want to go lighter, bleach will need to be used to physically remove them from the cortex.

All that said–this doesn’t mean that you need to have an entire 4-hour intense bleaching session that’s going to destroy your hair to get it a level or two lighter, either. This is where a soap cap comes in.

A soap cap is a mixture of shampoo, hair bleach, and developer. This creates a diluted bleach mix that easily distributes and emulsifies throughout the hair. This technique is fantastic for corrective color services when you need to fade or lighten color in a pinch.

7 Different uses for a bleach bath

Below I’ve mentioned the 7 most common ways you can use a bleach wash for corrective color services. I suggest finding the one that most closely matches your situation, then skipping below to learn how to do it.

1. If your toner takes too dark, ashy, or intense

If you’ve just toned your hair and it’s taken too dark, ashy, or your vivid color is too intense, you can use a soap cap to pull some of the toner out.

It’s not uncommon for toners to sometimes take on too “drab” if the hair was overly porous or if you didn’t add any warmth to the formula.

Or if your blonde canvas was too light and your vivid or fantasy color took way too bright and intense, you can do a shampoo cap to soften and dull the color. This will pull some of those color molecules out of the hair, essentially starting the fading process.

Depending on how long you leave your bleach wash on for, you can either lighten the toner slightly or remove it completely for an entirely new shade.

2. To lighten permanent hair color a level or two

If you have demi or permanent color on your hair and it’s too dark, you can use a bleach bath to lighten it up a level or so. This is commonly used when your hair is freshly colored and it’s darker than you’d like it to be.

Keep in mind that since the bleach is diluted, this technique isn’t meant to give you significant lift by skipping more than 2 levels. And the longer you leave it on, the more underlying, warm pigment that will be exposed as the color is removed.

So if you went WAY too dark, you may need more than a shampoo cap. But if you just want to bump it up slightly, this is a super-easy way to do it.

To learn more about the level system, see my post here.

3. To remove banding

Banding is characterized by visible lines of color or “bands” throughout the hair. There are numerous reasons why you may have wound up with banding in your hair. But some of the most common reasons are: overlapping, not using a lower developer volume on the scalp, using too dark of a color on the scalp, or improper application.

I’ve also seen banding after women give birth. Because of the overload of hormones, natural hair color is often darker when pregnant, and then goes back to a lighter color after giving birth. This can create a visible line from pregnant hair to non-pregnant hair.

Performing a shampoo cap focusing on the band will help to soften the band and create a more blended overall finished look.

4. To prep the hair for a new, lighter, or brighter color

If you’re wanting to switch things up, it’s smart to perform a soap cap to remove some pigment from the hair before applying your new color. This is especially helpful if your new shade is lighter, more intense (reds or coppers), or brighter than your last color.

The new shade will take much better and more evenly since the cuticle was opened up and some old color molecules were removed.

5. To remove purple shampoo buildup

If you’re a blonde and religiously use purple shampoo, you’re likely familiar with the dinginess that can come when you’ve used it too frequently. The hair can become a lavender or grayish color, and can become pretty dull if used excessively.

To fix this, a shampoo cap will help to pull that dullness right out to give you a fresh start. This is commonly done on the mids and ends of blonde hair when getting fresh highlights or a root touchup. The old purple shampoo needs to be removed for the new highlights at the roots to match the mids and the ends.

Then, a toner can be applied all over for an even result.

6. As a presoftener so that resistant hair takes the color better

If you have very healthy, coarse, or gray hair, then your hair is likely somewhat resistant. This means that the color doesn’t always “take” well, and you’re still left with gray hairs after coloring.

There are a few reasons why this happens, but typically your hair is not very porous, and it’s harder for the color molecules to penetrate the cortex to alter the color of the hair.

And in the instance of gray hair, the hair lacks melanin. So in this case, there’s just nothing for the color molecules to grab onto.

If you often experience this, performing a bleach bath prior to your color application as a “presoftener” will prep the hair for absorbing the hair color. And when I say “prep the hair”, I mean that the bleach wash will open your cuticle a little and make it easier for the color molecules to get where they need to in the cortex for the color to take.

7. To remove direct dye (semi-permanent color)

While I’ve shared methods for how to remove direct dye without bleach in the past, performing a soap cap is typically the go-to option if you aren’t completely against using bleach. This is much faster than other methods like the one I’ve shared before.

The shampoo cap will gently pull the semi-permanent color molecules out of the hair in a matter of minutes. You can use this to prep the hair for your next color or prior to going back to blonde.

When to NOT use a bleach wash

There are only a few instances where I would advise against using a bleach wash. The first is if you are using it on virgin hair and don’t plan on coloring over it. Since the application is roughly applied and processes very quickly, this isn’t going to look like highlights, nor is it meant to look like an all-over color application.

It’s meant to prep the hair for a new color application or to correct a color that took too dark. Not that you can’t carefully apply this to virgin hair and have it come out great. But this isn’t what the technique is intended for.

And the second is if you need more than 2 levels of lift. While this can be a good start to prep the hair for a bigger lightening service, the bleach is diluted too much to lift more than 2 levels.

Bleach wash tutorial

For a visual demonstration on how to mix and apply a bleach wash, see this video below.

***Since I’m sharing the products that I love to use with you guys, this page includes affiliate links to these products. If you take action and purchase a product through clicking one of my links, I’ll make some commission money from it at no extra cost to you. This enables me to be able to continue giving you awesome hair tips, so thanks! ***

How to mix a Soap Cap

I recommend using a clarifying shampoo to help remove any impurities and buildup from the hair, although any shampoo will work.

Typically, you’ll want to use 5 volume, 10 volume, or 20 volume developer. The stronger the developer, the faster the processing. If you’re not super experienced, I recommend starting with 10 volume and letting it sit on for longer if needed.

The ratio of shampoo to bleach to developer varies. Most stylists do not actually measure the ingredients, and eye it out instead to get a cake batter-like consistency.

The higher the bleach concentration, the stronger the bleach wash. The lower the bleach concentration, the weaker it will be. Since you’re likely not familiar with using bleach, see the table below for a guide on mixing ratios:

1:2:3 – Mild Lift

1 part bleach powder + 2 parts developer + 3 parts shampoo.

1:2:2 – Standard Lift

1 part bleach + 2 parts developer + 2 parts shampoo.

1:1:1 – Strongest Lift

Equal parts bleach + developer + shampoo.

How long to process a bleach wash

Anywhere from 1-30 minutes.

You’ll apply your soap cap to damp hair with gloves on and begin to process.

Your process time will vary significantly based on how much lift you’re looking to achieve, how fresh the color is you’re lifting out, how strong your formula is, and how porous the hair is.

There have been times I have let a soap cap process for 1 minute (just to slightly pull a toner that took a little too dark), and there have been other times I’ve processed them for 30 minutes (this is when you’re looking to lighten significantly and are doing this to prep the hair and remove as much color as possible first).

Because of this, you should continuously watch the hair. I like to continue emulsifying the product into the hair with my hands and not take my eyes off of it until it’s the desired shade I’m looking for.

If you aren’t planning on coloring the hair afterwards, err on the side of caution and process for less time (5 minutes give or take) to avoid removing too much color and exposing warm underlying pigment (unless you are okay with warm tones).

What to do immediately after a soap cap

Immediately following your bleach bath, you’ll want to shampoo the hair with a moisturizing shampoo to remove all traces of bleach and apply a deep conditioner in the form of a moisturizing treatment. Since bleach can also pull moisture out of the hair, it’s important to replenish that moisture.

Now if you were lightening up freshly colored hair that was too dark, you should be good to go at this point!

And if you were doing this to prep your hair for color, you can now apply your desired shade.

To learn more about the different types of deep conditioners, see my post here.

Conclusion

Soap caps are a lifesaver when it comes to corrective coloring. They’re a mixture of bleach, developer, and shampoo and are used to quickly fade hair color or lighten the color by a level or two. These are phenomenal when you need to budge your color in a pinch.

The 7 main uses for bleach washes are:

If your toner takes too dark, ashy, or intense
To lighten permanent hair color a level or two
To remove banding
To prep the hair for a new, lighter or brighter color
To remove purple shampoo buildup
As a presoftener so that resistant hair takes the color better
To remove direct dye (semi-permanent color)

If you have any further questions on how bleach baths work, leave them for me in the comments! And make sure to subscribe below if you want to make every day a good hair day.

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