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Additives & Chemicals
3% Hydrogen Peroxide (1000mL)
A 1 litre bottle of 3% hydrogen peroxide (10 volume) for spot-treating early cobweb mould and sanitising tools and work surfaces. It breaks down to water and oxygen and leaves no residue.
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Supplied for cultivation and lab use. Read the safety section before you open the bottle.
10 volume hydrogen peroxide, the standard dilute grade
Breaks down into water and oxygen only
For early cobweb mould, not a substrate sterilant
The short version
Hydrogen peroxide at 3%, also called 10 volume, is the dilute grade growers reach for when cobweb mould first appears. A fine mist bursts the loose grey hyphae on contact, then the peroxide breaks down into water and oxygen and leaves nothing behind.
It is a spot treatment and a surface sanitiser, not a cure-all. It will not rescue a heavily contaminated tub, and it should not be poured routinely onto substrate. Used early and sparingly, it buys you time.
What it is
What you are buying
This is a 1 litre bottle of hydrogen peroxide solution at 3%. In the older volume system that is 10 volume, meaning one part of the solution releases roughly ten times its own volume in oxygen as it fully decomposes. It is the same dilute strength sold as a general antiseptic and surface cleaner.
The chemistry is simple. Hydrogen peroxide breaks down into water and oxygen, so once it has done its job there is no chemical residue left on tools, surfaces or tissue. That clean breakdown is the whole appeal for lab and grow-room work.
| Concentration | 3% hydrogen peroxide (10 volume) |
|---|---|
| Volume | 1000 mL (1 litre) |
| Breaks down into | Water and oxygen, no residue |
| Reaction | 2 H2O2 to 2 H2O + O2 |
| CAS number | 7722-84-1 |
How to use it
Spot-treating early cobweb mould
Cobweb mould shows up as a loose, wispy, grey growth that spreads fast across the surface, often covering a coin-sized patch in a day or two. Caught early, a light mist of 3% hydrogen peroxide bursts the fine hyphae on contact, while established mushroom mycelium, which forms thicker white ropes, tends to shrug it off. The key word is early. This is damage control, not a guaranteed fix.
Identify first
Make sure it is cobweb mould and not healthy mycelium. Cobweb is greyer, looser and spreads across the top in hours, not days. Once a patch turns coloured, often pink, yellow or grey-green, it is sporulating and spraying it can spread spores rather than stop them. At that stage remove the tub instead.
Mist the patch
Decant a little into a clean spray bottle and mist the affected area and a small margin of the healthy surface around it, until just wetted. Do not soak the whole substrate. You can also lay a peroxide-dampened paper towel over a small patch.
Repeat if needed
The peroxide fizzes, kills on contact, then breaks down to water and oxygen. If the mould persists, growers usually repeat up to three times at roughly twelve-hour intervals. Stop once the patch is clear.
Do not keep dosing the same spot beyond that. Hydrogen peroxide is very weakly acidic, and constant wetting also keeps the surface damp, which favours other contaminants. Treat the spot, then stop.
Another use
Sanitising tools and surfaces
The 3% solution is handy for wiping down work surfaces and sanitising hand tools such as scalpels, scissors and tweezers between tasks. Because it leaves no residue, you are not transferring cleaning chemicals into your grow. Let tools air-dry before they touch substrate or culture.
Storage and safety
Keeping it and handling it
Hydrogen peroxide breaks down on its own over time, and heat and light speed that up. Store the bottle upright, closed, in a cool dark place. Sealed and stored well it holds its strength for a long time. Once opened it weakens over months, so buy what you will use.
It is a mild oxidising agent. Keep it away from metals such as copper, brass, iron and mild steel, which catalyse its breakdown, and store it in its original plastic or glass bottle rather than a metal container. Keep the original cap so the bottle can off-gas naturally rather than building pressure. Under UK GHS labelling the only hazard classified at 3% is serious eye irritation (H319), so eye protection is the main precaution.
| Store | Cool, dark, upright, closed |
|---|---|
| Avoid | Sunlight, heat, copper, brass, iron, mild steel |
| Eyes | Causes serious eye irritation (H319). Wear eye protection |
| Skin | May sting cuts or grazes. Rinse off if splashed |
| If splashed in eyes | Rinse with clean water for at least 10 minutes, holding the eyelids apart. Get medical advice if irritation persists |
| Keep from | Children and pets |
What it is not for
The limits
This is not a substrate steriliser. It will not replace pressure cooking or proper pasteurisation, and routinely soaking substrate in peroxide is not good practice. It will not save a tub that is already heavily overrun. And it is not a humidifier additive you should run as a matter of course, since that keeps your mushrooms in constant contact with peroxide mist.
Think of it as a first-response tool for early contamination and a clean, residue-free way to wipe down tools and surfaces. Used that way it earns its place on the shelf.
Common questions
Frequently asked
Established white mycelium usually tolerates a light spot mist, but repeated or heavy use can damage it. Treat the affected patch and a small margin around it, then stop.
No. It is not a substrate steriliser and routine soaking is not recommended. Use it to spot-treat early mould and to sanitise tools.
Mist it, then if the mould persists repeat up to three times at roughly twelve-hour intervals. Stop once the patch is clear.
Coloured cobweb, often pink, yellow or grey-green, is sporulating. Spraying can spread spores at that point, so remove the tub instead.
No, 3% is already the working strength. Use it as supplied.
Hydrogen peroxide naturally breaks down, faster in heat and light. Store it cool, dark and closed, and use opened bottles within a few months.
At 3% it is low-hazard, though peroxide can still sting the eyes. Wear eye protection, avoid eye contact, and rinse with plenty of water for at least 10 minutes if it gets in your eyes.
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Supplied for legal mushroom cultivation and laboratory use. Not for medical use. Causes serious eye irritation; wear eye protection. Keep out of reach of children and follow the safety guidance above.
We work hard to keep this information accurate and to cite reputable sources, but the occasional mistake can still slip through. Always check the product label and a current reference before relying on any figure for something important.