How Long to Leave Bleach in Hair Vol 40, 30, 20, and 10

Bleaching hair can lead to corrosion in the hair cuticle, brittleness, and hair breakage. This is why you need to learn how long you can leave bleach in your hair, especially with the different types of developer volumes.

There’s no textbook time as to how long to leave bleach in hair. However, the rule of thumb is the higher the volume(40/50) the shorter bleach should remain in the hair. So for the 40 volume, about 20 minutes is sufficient. Plus, your hair shouldn’t remain in bleach for longer than 45 minutes or you risk all the negative side effects of bleaching.

Follow us into the discussion as we answer common questions regarding bleaching your hair.

How Long to Leave Bleach in Hair 40 Volume

It shouldn’t be more than 20 minutes. An at least 40 volume hair developer is very concentrated with 12% hydrogen peroxide which means you only need very little contact with your hair. After 20 minutes, probably less, your scalp and areas around the face will start to feel like they’re getting burned. That’s your cue.

40 volume bleach duration in hair
Vol 40

How Long to Leave Bleach in Hair 30 Volume

Even with less percentage of hydrogen peroxide, it’s still strong and could also leave burns on the scalp not to mention sensitivity and irritability. The best time to leave the bleach in would be 15 to 30 minutes maximum.

volume 30, 20, 10 hair developers
Vol 30, 20, 10

How Long to Leave Bleach in Hair 20 Volume

A 20 volume hair developer is quite standard. It’s relatively safe and could stay in longer. From 20 to 40 minutes, it can lift the hair two to three tones lighter. It’s not entirely strong and could use another application so don’t leave the hair in too long expecting better results. That also applies to the next volume.

How Long to Leave Bleach in Hair 10 Volume

The 10 volume hydrogen peroxide developer is the lowest available concentration. It’s used on no loft dyes and best for beginners. Because of its low concentrations and gentleness, it can stay a maximum of 45 minutes. That should allow all the bleaching to occur. Besides your hair will still be safe and will have little to no hair damage.

How Long to Leave Bleach in Hair 50 Volume

Unfortunately, the 50 volume isn’t sold legally in many places around the world. The percentage of hydrogen peroxide in this developer is very high and riskier than any other. Even with stylists, aestheticians, and some chemists. You’d rather not use this volume.

If you do, it has a fast turnaround time of just 10 minutes. Any more will lead to hair damage, breakage, and split ends.

Factors that Will Determine the Duration

The type of hair volume developer used with the bleach isn’t the only thing you should consider with your timing. Other things come into play, for example;

  • Hair type
  • Starting color
  • Desired hair outcome
  • Type of developer
  • Bleaching frequency

Hair Type

Different hair types will react differently where fine thin hair will bleach faster than thick coarse hair. Virgin hair or natural hair may also take longer to bleach. Many factors surrounding the hair such as texture and porosity play a role in how the hair is lifted by bleach.

Starting Hair Color

There are different shades of hair from blonde, black, brunette, brown, and redheads. If you’re starting with dark brown or black strands, you’ll likely need to leave the bleach on your hair for longer to achieve the lightness you crave. Moreover, such shades may need more than one bleaching session to get to their intended lightness.

As for blondes, your hair is already lighter than all the other shades so you only bleach for a short while. This is also the case if you had already lifted the hair previously and are on your second or third bleaching process.

Desired Hair Outcome

Your hair goals will determine if one bleaching session is enough or you need a series of them. Also, if you simply want a subtle change then less time would be needed rather than the entire 30 to 45 minutes that lifts the hair two to three shades lighter.

So this simply means the longer you leave the bleach on your hair, the more your natural hair color will lift, and the lighter your strands will become. The lighter you want your hair, the more bleach you need.

Type of Developer

We have already touched on this in the above sections where we have mentioned the higher the volume, the less time you should leave the bleach on your hair. Remember to include all these other factors to get the right time.

Also note that different brands work in different ways so regardless of the volume of the developer, look at the instructions on the packet for further guidance.

Bleaching Frequency

Sometimes, you want to bleach your hair more than once to achieve a certain lift that would otherwise be impossible in one session. This means your subsequent sessions will last shorter than the initial one.

If your first bleaching session was 30 minutes, the rest would have to be shorter by five minutes or more. This will protect your hair from further damage from bleaching.

Ideally, if you’re only bleaching the roots, where the regrowth has happened, the time will also be shortened as the roots take a short time to bleach thanks to the heat around the scalp. This applies whether you use a high or low volume developer, preferably lower.

What Happens If You Leave Bleach on Your Hair for Too Long?

There have been speculations that the bleach mixture will only work for a certain period then it goes dormant. This is true to some extent meaning the bleach will only lift the hair about two to three shades, where a higher developer volume will lift more. However, other factors such as your hair type affect how much your hair can be lifted.

The mixture between the hydrogen peroxide and the bleach/ ammonia will not deactivate itself. So even though the hair isn’t getting lifted anymore, the mixture can adversely affect your hair causing dryness, hair breakage, and split ends.

Hence why keeping an eye on your hair as it processes is very important to minimize exposure times and subsequent hair and scalp damage. After 30 to 45 minutes of exposure to the hair, the bleach starts to eat at the hair’s keratin, making the strands weaker and brittle.

Other dangers that could occur if you leave the bleach on hair for too long include;

  • Your hair could lose its pigment and turn white. The hair contains melanin which gives it the natural look of blonde, black, brown, or red. With too much exposure to bleach, the open hair cuticles will be lifted to a point there are no more melanin molecules left.
  • Your hair turns extremely weak because it’s been oxidized by dyeing the decoloring process.
  • Your hair will be less able to absorb and retain moisture. Being weak is only one part of the problem, but the hair strands lose the ability to hold water molecules leaving them weak similar to during heat damage.
  • Skin that was exposed to the bleach will also be severely affected including loss of melanin, irritation, swelling, itching, among other problems.
  • Bleach has also been known to turn the hair highly porous. The hair cuticles can’t retain water because the cuticles are widely spaced and the hair is left with high porosity.
  • The hair will be severely dehydrated leading to the destruction of the hair shaft which may mean irreversible damage to the hair.
  • Your hair could lose keratin, the protein that makes up the hair. This means you’re likely to experience alopecia as hair starts to fall off, plus the hair will be brittle and hard to style.
  • On the extreme end, your hair could turn orange for those with naturally darker shades. Orange means the hair has been “cooked” long enough and it’s now very fragile.

These are the most prevalent side effects you can expect from leaving bleach in your hair for too long.

Further Reading: How Long Should I Wait to Bleach My Hair Again Without Damaging It?

How Do You Know When It’s Overstayed?

Bleach should be rinsed off when you have achieved your desired lift in your hair. Ideally, that shouldn’t be more than 45 minutes because the hair will stop lifting and start damaging. To prevent such damage to the hair, here are a few tips to ensure you know the right time to wash out the bleach.

  • Check your hair every ten minutes to confirm the lift in the hair. Frequency checking will ensure your time yourself and are aware of the changes throughout the process.
  • If at any point you start to feel pain or discomfort beyond the usual slight itching or tingling on your scalp, the bleach should be rinsed out promptly.
  • Follow the guidelines on the packet aligned with the other factors stated above.
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