A hydrogen peroxide and bicarbonate paste on a stain

Does it work?

Disputed

One half of the claim is affirmatively supported by a professional body, and the other half is the failure mode that same body warns about. The two ingredients do not behave the same way, and a single answer for the paste would lose that.

This is a verdict on whether the technique is effective. Whether it is safe on a particular surface is a separate question, answered below.

Where not to use it

The proposed mechanism

The explanation below is what is offered for this technique. No evidence establishes that this is what actually happens, so treat it as a plausible story rather than as a finding.

Two mechanisms are claimed at once: oxidation of the coloured part of the stain by the peroxide, and mild abrasion or alkalinity from the bicarbonate. Both ingredients do have those properties. What no authority addresses is the combination; what one does address is the consequence of leaving either behind — an unrinsed oxygen bleach continues to bleach, and an unrinsed solid attracts soil.

Background

The recipe is peroxide mixed with bicarbonate of soda into a paste, spread on a stain and left. Taking the two ingredients separately gives a much clearer answer than taking the mixture. Hydrogen peroxide at 3% is genuinely the professional residual-colour step: a certification body's consumer procedure ends with applying fresh 3% peroxide and leaving it on the stain until the result is reached, over several hours or attempts, with one explicit exclusion — not recommended for wool or other natural fibres without extensive testing for colour loss. It also warns that the bottle must be fresh, because peroxide decomposes on the shelf. The paste is where it goes wrong, and the same body describes the failure without naming the recipe. Consumer oxygen-bleach spotters bleach permanently if they are not rinsed immediately — usually yellow-brown on synthetics — and any solid left in the fibre is a residue that attracts soil and darkens later. A paste is the hardest form to rinse out of a pile. So: the oxidiser is supported and the vehicle is the problem. Use it as a liquid, on a synthetic, and rinse.

Conditions

• Where 3% hydrogen peroxide is used alone, as a liquid, on a synthetic fibre, and rinsed thoroughly afterwards

What it does not do

• Not recommended for wool or other natural fibres without extensive testing for colour loss
• Unrinsed oxygen bleach causes permanent bleaching over time, usually yellow-brown on synthetics
• A paste is the hardest form to rinse fully out of a textile, which is the condition the warning turns on
• No authority assesses the two ingredients combined, so the paste itself is unassessed
• Peroxide decomposes in an opened bottle, so an old bottle may do nothing at all

What to use instead

• Detergent — A surfactant-based cleaner. The general-purpose answer for greasy and particulate soil, and the correct first choice far more often than any specialist product.
• Blotting — Lifting a spill straight up into an absorbent cloth rather than working at it. The opposite of what almost everyone does, and the trade bodies are explicit about why.
• Sodium percarbonate (oxygen bleach) — An oxidising bleach that releases hydrogen peroxide in water. Gentler than chlorine bleach on fabrics and dyes, and it does not produce chlorine gas.