Every home brewer knows the sinking feeling. You lift the lid on the fermenter and there it is: a crusty ring of dried krausen welded to the plastic, a cloudy film creeping down the sides, and that faint sour whiff that tells you last batch left something behind. Or you drag a case of bottles out of storage and half of them are still wearing ghostly label glue and a scaly residue that a quick rinse won't shift.
Dirty gear isn't just ugly. Residue, scum rings and stained bottles are exactly where infections take hold, and a single contaminated batch can turn a month of patience into a drain pour. The first mantra of beer brewing exists for a reason:
Make sure your equipment is clean and sanitised — every single time.
There are plenty of ways to get there. My preferred method, and the one I've used on every brew for years, is sodium percarbonate. It's cheap, it's an oxygen-based cleaner that lifts organic gunk without scrubbing, it rinses clean, and you can order it in bulk online for a fraction of what the specialist brew shops charge for a little tub. This guide is the full story on what it is, the chemistry of how it works, and exactly how to use it on every piece of kit you own.
⚡ Quick answer
Sodium percarbonate is a powdered oxygen cleaner — washing soda plus hydrogen peroxide in solid form. Dissolve it in warm water and it releases active oxygen that oxidises and lifts organic residue off your gear.
- Dose: roughly 5–10 g per litre (about 1 tablespoon per 4–5 L).
- Water temperature: warm to hot, ideally 40–60°C — this matters more than anything else.
- Soak time: 20–30 minutes for routine cleaning, overnight for stubborn rings.
- Remember: it's a brilliant cleaner, not a guaranteed no-rinse sanitiser. Clean first, sanitise second.
What sodium percarbonate actually is
Sodium percarbonate looks like ordinary white powder, but it's a clever bit of chemistry. It's an adduct — a stable crystalline compound — formed from sodium carbonate and hydrogen peroxide. Its formula is usually written 2Na₂CO₃·3H₂O₂, and you'll sometimes see it called sodium carbonate peroxyhydrate. Think of it as a dry, shelf-stable way to carry hydrogen peroxide around until you need it.
That's worth pausing on, because the name trips people up. Sodium carbonate on its own is plain old soda ash or washing soda — a salt made from sodium and carbonic acid, used in glass, soap and detergent making. It cleans, but gently. Percarbonate is that same washing soda with hydrogen peroxide locked into the crystal, and it's the peroxide that turns a mild cleaner into a proper oxygen-powered one.
💡 Don't confuse your sodas
Sodium percarbonate is the oxygen cleaner. Sodium bicarbonate is baking soda — you're cleaning a fermenter, not making a cake. And plain sodium carbonate (soda ash) is the washing-soda half of percarbonate without the peroxide punch.
The science: how oxygen cleaning works
The moment percarbonate hits water, it splits back into its two ingredients:
2Na₂CO₃·3H₂O₂ → 2Na₂CO₃ + 3H₂O₂
In plain English: the solid dissolves into washing soda and hydrogen peroxide. Now you've got two cleaning mechanisms working at once, which is why percarbonate punches above its weight.
1. Alkalinity does the heavy lifting on soil. The sodium carbonate pushes the solution alkaline — pH 10 to 11. That high pH saponifies fats and oils and loosens the grip of proteins and other organic gunk, exactly the stuff a beer leaves behind. It also softens the water so the cleaner works better.
2. Active oxygen does the oxidising. The hydrogen peroxide breaks down and releases oxygen:
2H₂O₂ → 2H₂O + O₂↑
Those bubbles aren't just for show. As the peroxide decomposes it produces reactive oxygen that chemically attacks and breaks apart organic molecules — stains, residue, dried krausen, the lot — while the stream of oxygen bubbles physically lifts loosened soil off the surface and floats it away. That combination of oxidising and mechanical lift is why a good percarbonate soak shifts grime that would otherwise need a lot of elbow grease.
Because the active ingredient is oxygen and the by-products are water, oxygen and soda ash, there's no chlorine and no harsh residue left behind. That's a real advantage over chlorine bleach, which can leave chlorophenol off-flavours in beer and pit stainless steel. Percarbonate does its job and breaks down into things you don't have to worry about.
Cleaning is not sanitising — and why that matters
This is the single most misunderstood point in home brewing, so let's be precise. There are three different jobs, and they're not the same:
- Cleaning removes soil — the visible and invisible organic residue, oils, proteins and film left on a surface.
- Sanitising reduces the microbes on an already-clean surface to a safe level.
- Sterilising kills essentially everything. It's rarely achievable in a home kitchen and rarely necessary.
Here's the honest correction that saves batches: you cannot sanitise a dirty surface. Soil physically shields bacteria and wild yeast, and it chemically burns through sanitiser before it can do its job. That's why the pros say it over and over — clean first, sanitise second. As one recent piece on this site argues, treating sanitiser as a magic fix while ignoring the residue underneath is exactly why sanitisation quietly fails so many brewers.
So where does percarbonate sit? It is primarily a cleaner. Its high pH and active oxygen do give it genuine antimicrobial punch — especially with hot water and a long soak, which is why a thorough percarbonate soak leaves gear in very good shape. But it is not a registered no-rinse sanitiser, and I'd never tell you it replaces one if you want belt-and-braces insurance right before you fill. For the full run-down on why you sanitise brewing equipment and how, that's a rabbit hole worth going down.
In practice, I clean and soak so thoroughly that I've brewed for years on percarbonate alone with no infections. Plenty of brewers do the same. But the choice is yours, and if you like the reassurance of a dedicated sanitiser as a final step, that's a completely reasonable call — more on the options below.
How to use it: concentration, temperature and soak time
Mixing it couldn't be simpler: add the powder to water and stir. But three variables decide how well it actually works, and most brewers get the temperature one wrong.
Get the water temperature right. If you take one thing from this guide, take this: warm water transforms how well percarbonate works. The reaction that releases active oxygen speeds up sharply with heat, and tests consistently find temperature outranks both concentration and soak time for cleaning power. Cold water leaves half the cleaning on the table.
💡 The honest correction on boiling water
I used to tip boiling water straight into the drum to kick the reaction off fast, and the heat does help. But flat-out boiling actually burns off the hydrogen peroxide too quickly, so you lose oxidising power before it's done its work. Hot-tap-to-just-steaming (40–60°C) is the sweet spot — hot enough to fire up the oxygen, not so hot you waste it.
The method I use:
- Add a generous scoop of powder to the fermenter and pour in hot water to dissolve it — it goes into solution almost instantly.
- Top up so the solution covers every soiled surface, or fill right to the top for a stubborn ring.
- Pop the lid on loosely so the vapour works up the sides. Do not seal it tight while it's hot and active — the oxygen it releases will build pressure.
- Let it soak. Twenty to thirty minutes for a normal clean; overnight if I've remembered the day before.
- Once it's cooled a little, a good swirl or gentle shake helps. Mind the hot water coming back out of the lid hole.
My thinking is simple: the longer it soaks, the more the alkalinity and oxygen get to work. One nuance worth knowing — the active oxygen is largely spent within a few hours, so an overnight soak does its later work mostly through alkalinity. That's still plenty to loosen a set-in ring, which is exactly what you want it for.
Clean first, then let the percarbonate finish the job
Percarbonate is the final stage of cleaning, not a substitute for getting the worst off first. If there's a thick line of scum at the water mark or a slab of trub in the bottom, get in there with a soft brush and really hot water and knock the bulk of it off before you soak. You want the percarbonate working on a broadly clean surface, not a science experiment.
For the pre-clean, warm water and a soft sponge handle most of it — and yes, a bit of dishwashing liquid is fine on fermenters and bottles as long as you rinse well. For a heavier-duty cleaner you can use PBW or even make your own brewing wash. Small utensils can take a turn through the dishwasher too — the heat helps.
⚠ Go easy on plastic
Never attack a plastic fermenter or bucket with an abrasive scourer. The scratches you leave become permanent hiding spots for bacteria that no soak can reach — a soft brush or cloth only.
Cleaning specific gear: fermenters, bottles, tubing, taps, airlocks and spoons
The same warm solution handles almost everything, but each bit of kit has its own knack.
- Fermenters: fill or half-fill with warm solution, soak, then a soft-brush wipe of the ring and a thorough rinse. This is the workhorse job — here's the full walkthrough on cleaning and sanitising your fermenter drum.
- Bottles: submerge them in the solution and let the oxygen do the work. It loosens dried beer residue and, brilliantly, lifts old label glue so labels float or peel off with no scraping.
- Tubing and hoses: fill them completely and soak — watch for trapped air pockets that stop the solution reaching the inside wall. Flush through thoroughly afterwards.
- Taps, valves and fittings: take them apart before you soak. Threads and fittings are where the worst infections hide, and a solution can't clean a surface it can't reach.
- Airlocks, spoons and small plastics: drop them in the same bath, soak and rinse. Simple, but don't skip them — an airlock touches your beer's headspace for weeks.
When to reach for something else
Percarbonate is my default, but it isn't the only tool, and part of using it well is knowing its limits. Here's how the common products compare.
| Product | What it is | Cleans? | Sanitises? | Best for |
|---|---|---|---|---|
| Sodium percarbonate | Oxygen cleaner (washing soda + peroxide) | Yes, excellent | Partly, with heat + time | Everyday cleaning and soaking of all gear |
| PBW | Buffered alkaline brewery wash | Yes, very strong | No | Heavy baked-on soils, gentler on skin |
| Star San | Acid sanitiser (phosphoric acid + surfactant) | No | Yes, no-rinse | Final sanitising just before you fill |
| Caustic soda | Sodium hydroxide, very strong alkali | Yes, aggressive | No | Extreme deposits only — handle with care |
Star San, the sanitiser everyone recommends
Read any brewing forum and someone will pop up swearing Star San is the best thing they've ever used. They're not wrong about what it does. Star San is a bactericide and fungicide built on a blend of phosphoric acid and dodecylbenzenesulfonic acid, and at the right dilution it sanitises without rinsing. A long way from Kansas, Dorothy.
The key thing to understand is that Star San sanitises — it does not clean. It's the perfect partner to percarbonate, not a competitor: percarbonate strips the surface clean, Star San kills whatever survived just before you fill. If you want that final layer of insurance and can't find it locally, you can grab Star San online or from Amazon.
Caustic soda for truly stubborn deposits
If you've got a fermentation scum ring that simply won't budge, caustic soda (sodium hydroxide) will shift it. But be warned: it's an extremely strong agent and it demands gloves, eye protection and a very thorough rinse.
⚠ Caustic soda will burn you — I know from experience
As a young bloke I worked at a fast-food chicken joint, and while mixing caustic soda to clean the floor a single drop got in my eye. It burned so badly I ended up in hospital and wore an eye patch for a week. Treat it with total respect: gloves, goggles, careful handling, and a proper rinse afterwards. For 99% of home brewing, percarbonate does the job without any of that risk.
You've probably already got some in the laundry
Here's a trick that saves money: sodium percarbonate is the key active ingredient in most "oxy" laundry soakers. Products like Tide, Napisan, OxiClean or any brand leaning on the word "oxy" are, at heart, percarbonate blended with fillers and fragrances.
That's right — most of those fancy laundry soaking products have sodium percarbonate as a key ingredient.
Chances are there's a tub in your laundry right now, and I've used it for brewing many times with zero problems. The percentage of percarbonate is lower than buying it pure, but it works. A couple of things to keep in mind:
- Go unscented if you can. Non-scented house brands are ideal. A scented one can leave your fermenter smelling like a lavender field — rinse with plenty of water if that happens, or you might add an unexpected note to your beer.
- Rinse well, then rinse again. If a supermarket product's smell or residue worries you, flush the gear with cold water, then finish with a rinse of freshly boiled kettle water. Call it a mental comfort or a final bug-killer — either way it settles the nerves.
💡 Want to know exactly what's in it?
Ask your supplier for the Safety Data Sheet. In New Zealand and many other countries these products must be registered and an SDS provided on request, listing the ingredients. That said, we're probably overthinking it — a plain oxy laundry soaker is a cheap, reliable source of percarbonate. And if the whole idea still spooks you, take a step back and have a Kit-Kat.
Common mistakes to avoid
- Expecting it to sanitise a dirty surface. It's a cleaner first. Knock off the gross soil, then soak.
- Using cold water. The biggest performance killer. Warm to hot, always.
- Soaking aluminium. Alkaline cleaners etch and blacken soft aluminium — keep percarbonate away from ally pots and use it on plastic, glass and stainless.
- Sealing the container tight. Active solution keeps releasing oxygen; a sealed vessel can build pressure. Leave the lid loose.
- Scrubbing plastic with an abrasive pad. Micro-scratches harbour bacteria for good.
- Skipping the rinse on scented products. Fragrance and residue can carry into the beer.
Safe handling, storage and disposal
Percarbonate is far friendlier than caustic soda or bleach, but it's still an alkaline oxidiser, so treat it sensibly.
- Handling: wear gloves for long exposure and keep it out of your eyes. The dust is a mild irritant — don't breathe it in.
- Storage: keep it dry, cool and sealed away from moisture. Damp percarbonate slowly loses its active oxygen and can build gas pressure, so if a tub has taken on moisture, don't clamp the lid down hard.
- Keep it apart: as an oxidiser, store it away from acids and flammable materials, and never mix it with other cleaning chemicals.
- Disposal: this is the easy part — a used, diluted solution breaks down into soda ash, water and oxygen. It's safe to pour down the drain with plenty of water, with no chlorine or phosphate nasties to worry about. Just keep the powder well out of reach of kids and pets.
Troubleshooting
- Film or residue after a soak: rinse with hot water. A white haze is usually hard-water scale, not the cleaner — a quick rinse, or a mild acid rinse in hard-water areas, clears it.
- Labels won't come off bottles: go hotter and longer. A warm overnight soak lets the oxygen work under the glue until labels lift on their own.
- Lingering odour: almost always a scented laundry product. Rinse copiously, or switch to unscented or pure percarbonate.
- Stubborn scum ring: start hotter, add another scoop, and leave it overnight. If it still resists, step up to PBW or, as a last resort, caustic soda with full precautions.
- No fizz, weak cleaning: the product has probably aged and lost its active oxygen. Replace it and store the new tub bone dry.
Sachets versus bulk: keeping a tub on hand
Most starter kits come with a little sachet of "no-rinse" cleaner, and it's almost certainly sodium percarbonate. Don't get sucked into buying those at a dollar-fifty a pop. Like your grains and hops, this is something to buy in bulk once you're brewing regularly — the cost per brew drops to almost nothing, and a full tub in the cupboard means you'll never talk yourself out of a proper clean because you're low on cleaner.
If you buy the specialist brew-shop tubs you'll pay a small fortune for a small container. Buying it in bulk from an online supplier is far better value, and it keeps for ages stored dry. New Zealand brewers can also check what's listed on Trade Me, and if you're in the United States there's bulk sodium percarbonate on Amazon too.
💡 Bonus use
A tub of percarbonate isn't just for the brew day. It's oxygen bleach — about 1 cup to 4 litres of water will clean roughly 10 square metres of outdoor wooden deck. Handy to have around.
The bottom line
Cleaner equipment makes better beer, and sodium percarbonate is the simplest, cheapest way to get there. It's an oxygen cleaner that lifts organic residue, scum rings and old labels with a warm soak and almost no scrubbing, it breaks down into harmless by-products, and it rinses clean. Remember the one rule that overrides everything: it's a superb cleaner, so clean thoroughly first, and add a dedicated sanitiser as your final step if you want the extra insurance. Keep a bulk tub on hand and you'll never cut a corner you'll regret.
One last habit worth keeping: before capping your beer, hold each bottle to the light and check it's spotless with no creepy-crawlies hiding in the bottom. Five seconds now saves a ruined bottle later.
New to all this? Start with the simple step-by-step guide to home brewing, get your cleaning sorted here, and when the beer's in the bottle, read up on storing and conditioning your bottled homebrew so all that clean, careful work pays off in the glass.
