🚨 CODE RED: Can You Use 40 Vol Peroxide on Scalp?

For many hairdressers, the idea of using 40 vol peroxide on the scalp feels risky. Maybe you were taught that it’s too strong, unsafe, or only meant for off-scalp use. But is that actually true?

The answer is yes—but only when used correctly.

Understanding when and how to use 40 vol peroxide can be a game-changer for achieving vibrant coppers and strawberry blondes without needing bleach. In this blog, I’ll break down the key scenarios where 40 vol can be a powerful tool in your colour kit and when it should be avoided.

Show notes for episode 190

When Is 40 Vol Safe for On-Scalp Use?

While some stylists shy away from 40 vol, it can actually be a vital tool for lifting and enhancing warm tones. Here are the situations where it works best:

40 Vol + High-Lift Tint for Red & Copper Shades: For levels 6 & 7, 40 vol peroxide with high-lift tint is an excellent option to achieve peachy, golden, and strawberry blonde tones without pre-lightening. Unlike bleach, high-lift tint lifts while maintaining warmth, making it a great choice for reds and coppers.

Lifting Darker Bases (Levels 3 & 4) to a Rich Copper: Not all clients need bleach to achieve a vibrant copper. 40 vol mixed with high-lift tint can successfully lift levels 3 & 4 to a level 7 copper. It’s a gentler option compared to bleach and can result in a more natural-looking, dimensional lift.

When Maximum Lift is Needed with Permanent Colour: Some permanent colour formulas allow 40 vol peroxide to be used when extra lift is required. This is particularly useful when working with darker natural bases that need an extra boost. However, always follow manufacturer guidelines to prevent over-processing.

What to Avoid when using 40 vol peroxide on scalp

While 40 vol is a great tool in the right situations, it’s important to know when not to use it:

Never mix 40 vol with bleach for on-scalp use. This can cause major scalp irritation, excessive damage, and breakage. Bleach and 40 vol should only be used together in foils or off-scalp applications.

Avoid overlapping on previously lightened hair. This can lead to uneven colour, increased porosity, and unnecessary damage.

Not suitable for sensitised or compromised hair. If a client’s hair is fragile or has been chemically treated multiple times, 40 vol may be too strong and could lead to breakage.

Want to Master Reds & Coppers Without Mistakes?

If you want to take your copper and red formulations to the next level, my livestream class CODE RED: Principles of Red & Copper Hair Colouring is happening next week.

In this 3-hour live class, I’ll be teaching you how to:

✔️ Retouch copper without creating unwanted root glow
✔️ Colour grey copper clients seamlessly
✔️ Avoid banding and browning out for long-lasting reds

If you’re tuning in later, don’t worry—you can still access my online courses, in-person workshops, and in-salon training programs.

All the important links are shared below, including the ticket link for CODE RED and the link to learn more about my signature program Hair Painting for Redheads.

Listen to episode 190 of the Colour Kristina Talks Podcast to know if 40 vol peroxide is safe for on-scalp use and and how to use it safely for vibrant copper and strawberry blonde results.