Contents
Hydrogen peroxide in a cream base, mixed with colour or lightener to make the reaction happen. Developer is the component that decides how much lift a service produces and how much damage it does, and choosing the volume correctly is the single most consequential decision in hair colour.
What "volume" means
Volume is an old measure: the number of litres of oxygen gas one litre of the solution can release. It maps directly onto percentage.
| Volume | H₂O₂ % | Lift on natural hair | Use |
|---|---|---|---|
| 10 | 3% | None — deposit only | Demi-permanent colour, toners, glosses, going darker |
| 20 | 6% | 1–2 levels | Grey coverage, standard permanent colour, on-scalp bleach |
| 30 | 9% | 2–3 levels | Off-scalp lightening, foils |
| 40 | 12% | 3–4 levels | High-lift colour, off-scalp only, professional judgement |
More volume is not better. The common home-colouring error is reaching for 30 or 40 volume to get a stronger result; what it actually produces is scalp irritation, uneven lift and damage, because higher peroxide is more aggressive on the scalp and processes too fast to control.
Two useful facts that follow from the table: 10 volume cannot lighten anything, which is why demi-permanent colour is deposit-only; and 20 volume is the ceiling for on-scalp bleaching in almost every case.
What it actually does
Two jobs at once in an oxidative colour service:
- Oxidises melanin, breaking the natural pigment into colourless fragments — the lift.
- Oxidises the dye precursors inside the cortex so they couple into large coloured molecules — the deposit.
In a Permanent Wave it does a different job entirely: neutralising, re-forming the disulfide bonds the reducing agent broke.
Handling it
- Gloves, always. Peroxide at 6% and above burns skin and bleaches fabric on contact.
- Eye protection is not excessive when mixing 30 or 40 volume.
- Never decant into an unlabelled bottle, and never into a food or drink container. Developer looks like a white lotion.
- Mix in a non-metallic bowl. Metal ions catalyse peroxide decomposition and can ruin the mixture.
- Never seal mixed product in a closed container. The reaction generates oxygen gas and will burst it.
- Keep it away from children. Ingestion of concentrated peroxide is a genuine medical emergency.
Where it sits in the rules
Cosmetic in the US — FDA primary category (07) hair colouring preparations — sold over the counter with no premarket approval. Forty-volume developer is available to anyone.
FDA requires cautionary labelling, and MoCRA adds facility registration, product listing, safety substantiation records and serious adverse event reporting within 15 business days.
The EU is materially stricter: hydrogen peroxide is restricted under Annex III to 12% (40 volume) in hair products, with mandatory warnings including "Contains hydrogen peroxide", "Avoid contact with eyes", "Rinse eyes immediately if product comes into contact with them" and "Wear suitable gloves". Oral-care limits are far lower — see Whitening Gel — which is a useful illustration of how use-specific these limits are.
Shelf life
Unopened, two to three years. Once opened, peroxide decomposes continuously into water and oxygen, accelerated by heat, light and metal contamination. An old bottle lifts less and unpredictably, and unpredictable lift in a colour service means an uneven result.
Store cool, dark, upright and tightly closed. A bottle that has swelled has been generating gas and should be opened carefully and discarded. Mixed developer is used immediately and never stored.
Related
- Hair Colour — the shelf this sits on, and the rest of it.
- Cosmetics — what the label is legally allowed to say, and the full catalogue.
- The rest of Lifting — Hair Bleach · Hair Lightener · Highlighting Kit.
- Permanent Hair Dye · Demi-Permanent Hair Colour — the two things it is mixed with.
- Regulatory statements here follow the FDA and EU sources listed on Cosmetics, read 16 August 2026.