How Long Do You Leave Your Hair In Bleach?

hair bleaching kit - bowl, brushes, gloves on a blue background

If going platinum blonde is just too tempting but you’re on a budget and need some quick at-home lightening treatment you may be wondering, “How long do you leave your hair in bleach?”

Maybe you’re going through a breakup and need a fresh new look, or maybe you’re having a mid-life (or even quarter-life) crisis and you need a clean slate. Don’t worry, I’ve got you. Using bleach is a tricky and delicate process that requires adequate research before beginning.

While bleach can and ultimately will lighten your hair, there are some less than ideal scenarios that can occur when using this abrasive chemical as part of your go-to hair color routine, so it’s important to understand the risks involved.   

Bleach is powerful and works quickly, so ensuring you have thorough knowledge of what you’re doing before attempting to lighten your hair is of ultimate importance.

Hair damage, scalp irritation, chemical burns, and a general sense of unpredictability when it comes to the final result can all occur if not done properly. 

However, if dishing out hundreds of dollars at the salon is just not in the cards for you right now let me be the first to tell you: I don’t judge. So, that brings us back to our original question—how long to leave bleach in your hair.

This article will go through exactly how long bleach is meant to be left on your hair to ensure you don’t end up with chemical burns, or worse, bald.

How Long Should You Leave 20 Volume Bleach On For?

If the word ‘volume’ confuses you let’s break it down a bit: Volume is essentially the amount of hydrogen peroxide in a solution. The higher the volume, the more hydrogen peroxide within, and the stronger it will be.

The stronger the volume, the more capable it is to lighten your hair. So, for example, if you want to lift your hair 1-2 shades you would use a 10 volume developer. If you want to lift your hair 3-4 shades you would use a 20 or 30 volume developer.

Depending on the shade, texture, and overall health of your natural hair before bleaching, the amount of time 20 volume developers should be left on the hair varies. 20 volume bleach should be left on the hair for no more than 30 minutes.

Although, 30 minutes can still cause chemical burns, so be sure to check the progress frequently and abort mission if you feel any sensations of pain. If this is your first time bleaching your hair at home, start with 15 minutes to avoid any irreversible damage. 

How Long Should You Leave Bleach In Your Hair If It’s Black?

Bleaching black hair in general, but particularly at home, is a huge risk and anyone in the beauty industry will advise you to see a professional. Nonetheless, if you are dead set on bleaching your black hair you should have an idea of how long to keep bleach in your hair for. 

You’ll need to visit a beauty supply store and pick up a bottle of 30 volume bleach—anything stronger could easily burn you, so even if it makes sense to you that 40 volume will bleach your black hair faster—no it won’t. You will end up with dry, brittle, vulnerable hair. 

Leave your bleach on for no more than 45 minutes, any longer can cause accidental chemical burns. When bleaching black hair—especially chemically dyed black hair—the most common end result is a brassy, orange, copper color. 

Attempting to get a platinum blonde look from one session of at-home bleaching is quite nearly impossible, and trying to do so can greatly damage your hair for a long, long time. One of the biggest risks when bleaching black hair is the damage and loss of keratin (protein that makes up hair, skin, and nails).

It’s impractical to think avoiding keratin loss is possible when using bleach in general, but with the high strength of volume and bleach needed to go from dark to light, it is almost certain to completely strip the hair of it’s natural proteins.

With all of this being said, there is a “safer” way to bleach black hair from home—it just requires being informed and having lots of patience. If your mind is truly set on going blonde, be aware it will most likely take 3-4 sessions to achieve the color you want.

Let your hair rest for 2-3 weeks between sessions to allow adequate time for the hair to begin repairing itself. You may look in the mirror and realize your hair is the color of a carrot, however, resist the extreme urge to bleach it again immediately. 

Black hair first turning to a red-orange hue is completely normal and nothing to panic about. Instead of reaching for the bleach right away, use a purple toning shampoo to combat some of the brassiness. Purple shampoo is highly effective and much less harsh.

*Pro-tip: Using a purple shampoo as a hair mask can be even more effective at ridding your hair of that stubborn orange hue. Apply generously to hair and let it sit for 15 minutes before rinsing off.

Don’t let it sit TOO long, or you’ll start to see purple strands stick around! Performing a strand test is also highly recommended—as attempting to go blonde from black will require the strongest ingredients and you want to ensure there’s no risk of an allergic reaction. 

How Long Do You Let Bleach Sit Before Washing?

How long you should leave bleach in your hair all comes down to each individual person’s hair type. Different shades require more or less time, as does different hair texture. 

  • For those with naturally lighter, delicate hair, bleach should sit for around 15-30 minutes. 
  • For those with coarse, thick, or darker hair, bleach should sit in hair for around 30-45 minutes. 

While bleach is an aggressive chemical, these rules aren’t set in stone. There is slight room for flexibility as long as you’re being proactive in keeping an eye on the process. Making sure you’re consistent in checking the hair’s lightening process is crucial.

The first check should occur between 10-15 minutes. If you aren’t feeling any pain or discomfort, checking in 5 minute intervals until you reach 30 minutes is sufficient. Bleach should never, ever be left on any type of hair for longer than 45 minutes. 

It’s a common misconception that the longer bleach is left on the hair, the lighter your hair will become. This is simply not true. As with any other hair dye, the hair follicle can only take so much before it will reach a maximum threshold it can absorb.

Leaving bleach on hair for too long is a risky and dangerous game to play. No matter what your hair color or texture, do not—and I repeat, DO NOT lose track of time when bleaching your hair! This can lead to serious chemical burns along your scalp, which is just about as fun as it sounds. 

Do You Shampoo After Bleaching Hair?

Since bleach is not only aggressive but highly potent, you absolutely need to shampoo your hair after coloring to ensure all the chemicals have been removed. However, be gentle and considerate of the state of your hair post-bleaching. 

Bleach strips the hair of moisture and shampooing may further this so don’t scrub like your life depends on it. It’s recommended to rinse not only the bleach but shampoo and conditioner out with cool water.

Hot water strips your hair of moisture, and with the damage from the bleach already doing this job, using cool water can help keep the cuticle closed and retain any moisture the hair has left. 

After shampooing, use a deep conditioner or a conditioning mask and let it sit for a few minutes. Give your hair a long, tall drink of hydration after bleaching to retain strength and avoid breakage from being overly dry. 

Does Leaving Bleach In Longer Make Your Hair Lighter?

In a nutshell: no, leaving bleach in longer does not make your hair lighter. As a general rule of thumb, unless instructed by a hair care professional, do not leave bleach on your hair for over 45 minutes.

After 45 minutes the bleach has lightened the hair as much as it possibly can, so it begins to chemically damage the hair instead. Leaving bleach on for longer than 45 minutes will not make your hair lighter, it will result in dry, brittle, coarse, damaged hair follicles and in the worst-case scenario, cause irreversible damage. 

How Long Do I Leave 30 Vol Bleach In My Hair?

Ideally, 30 volume developer and bleach should sit in the hair for 15-30 minutes. A 30 volume bleach mixture will quickly lighten your hair but make sure you’re checking on the progress every 10 minutes to avoid over-lightening or damage. 

Hair all the way at the root is more susceptible to the effects of bleaching, so initially apply the bleach about an inch of the way down from the roots to the ends and leave the hair roots for the last step. 30 volume bleach shouldn’t be left on the roots for any longer than 15 minutes. 

How Do I Bleach My Hair With 30 Volume?

With about 9% peroxide, 30 volume developer will lift the hair’s color by about 2-3 shades. 30 volume developer is a great choice if you’re looking to lighten up your locks without going too crazy off the color wheel. 

Basic steps when bleaching hair with 30 volume developer:

  1. Mix a ratio of developer and bleach 2:1 (2 parts developer, 1 part bleach).
  2. Apply bleach using a dyeing brush, starting in the back of the head.
  3. Check your head every 5-10 minutes to avoid over-bleaching. 
  4. Allow bleach to sit for the allotted time depending on your natural starting color and hair texture.
  5. Rinse with moisturizing shampoo and a deep conditioner.

How Many Levels Will 30 Volume Lift?

30 volume will lift your hair about 2-3 levels on average. If your hair is black or a deep brown, it may only lift your hair 1-2 shades. If your hair is naturally a lighter shade to begin with, it may lift the entire 3 shades. 

If you don’t automatically achieve the lighter color you desire, it’s advised to wait a few weeks in between bleaching sessions to avoid damage to the hair or your scalp. 

Is 30 Volume Bleach Bad?

While no hair care products containing toxic chemicals are necessarily good for you, it’s unlikely 30 volume bleach will significantly damage your hair—as long as proper rules and protocol are followed. 

This includes doing sufficient research and wearing protective gloves and/or eyewear. A face covering is also an option to protect you from breathing in harmful fumes.

30 volume should never be used as an all-over color, as it will bust the hair cuticles wide open and greatly heighten the risk for long-term damage. 30 volume developer works quite fast and should never be put under a heat lamp or used with foils, as it will likely over-process the hair. 

Open air drying is the best way to ensure 30 volume developer isn’t causing permanent damage. In addition, 30 volume developers are generally used on darker or more textured hair. For those with lighter natural shades, 10 or 20 volume developers are entirely sufficient. 

How Long Should I Leave 40 Volume Bleach In My Hair?

Using any volume of developer over 30 can cause injury to the scalp and unnecessary lightening to the hair. Due to the high saturation of hydrogen peroxide in 40 volume developers, it’s often strongly recommended to be wary when purchasing for at-home use.

However, 40 volume developer is used by salons and hair professionals for clients with stubborn, permanent hair dyes that are aiming to go up to 8 shades lighter. Eight shades is possible, but unlikely. 

It is recommended to keep 40 volume developers in hair for no longer than 20 minutes. If the desired color isn’t reached in 20 minutes—try again in a few weeks, but don’t leave the developer on for more than 30 minutes, max. 

How Many Levels Will 40 Volume Lift?

A 40 volume developer, on average, lifts 3-4 levels on the hair color scale. Nevertheless, it does have the ability to lift up to 8 shades lighter. Hair care professionals often firmly advocate against using any volume over 30 when bleaching your hair at home.

This is due to the 40 volume bleach’s powerful force, producing detrimental consequences if not handled properly. Using 40 volume developer is often recommended for ultra stubborn darker colors.

In addition, it’s used when lightening the hair in combination with bleaching powders or creams in an attempt to achieve that ultra platinum blonde look. 

Furthermore, for those with thick hair, 40 volume developer may be the only strength that does the trick. In instances where the hair color starting off is quite dark, 40 volume should be used to ensure the developer can adequately penetrate into the hair shaft. 

Is 40 Vol Bleach Strong?

If you’ve read this far into the article you will know by now that 40 volume developer is, in fact, extremely strong. With its 12% peroxide makeup, it is strongly advised to NOT attempt to use 40 volume developer at home and/or if you have no prior experience bleaching your hair. 

A few risks of using 40 volume bleach incorrectly are:

  • Hair burns 
  • Scalp burns 
  • Extreme breakage 
  • Over dryness
  • Hair damage/frizz
  • Brittle, split ends

All in all, unless you have thick, coarse, or very dark hair naturally, there’s virtually no reason to use a 40 volume developer. Take a step back and use a 30 volume developer. You will still get to your desired color, it just may take a little bit longer—but will keep your hair much healthier. 

Final Thoughts: How Long Do You Leave Your Hair In Bleach?

So, how long do you leave bleach in hair for? Well, the answer isn’t as simple as one would like—as it all comes down to the texture, type, and color of each person’s unique hair makeup. However, as a general guideline, don’t ever leave bleach sitting in your hair for over 45 minutes.

Ideally, bleach should sit in your hair for 15-30 minutes to avoid uncomfortable and unpleasant side effects. Bleach can be dangerous and if you’re thinking about bleaching your hair at home make sure you take all the proper precautions beforehand to cut down on your risk of chemical burns or extreme hair damage.

The safest way to bleach hair at home is to start with basic research. Talk to a professional to find out what your hair type is and take into account any color that may still be in your hair from past months.

Buying volume and bleach from a beauty supply store directly is recommended, as most employees will be able to assist you in choosing the correct volume developer for your hair type.

After purchasing, make sure you wear protective equipment like gloves, to ensure you’re not penetrating the skin directly with bleach. Once the bleach is applied, allow it to sit for 10-15 minutes, then proceed with 5 minute intervals until the desired color is achieved.

Never, ever, let your hair sit in bleach for more than 45 minutes. Make sure to set a timer so that you don’t lose track of time while you binge-watch Stranger Things for the 3rd time. 

Bleaching your hair at home is possible with the right guidance, high amounts of patience, and sufficient knowledge of the bleaching process. Rock that quarter-life crisis, make that ex-boyfriend jealous and flaunt your new blonde locks, just make sure to do it safely, it will make a world of a difference.

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By Emma Eliason

Emma Eliason is a beauty writer at Kintegra Research. She has a passion for makeup and both skin and haircare. She is also a mom to a little girl whom shares the same love for beauty as Emma does. Emma is regularly trying out new products and always looking for the best!