Homebrew Troubleshooting: How to Fix Cloudy, Sour, Flat and Off-Tasting Beer and Stop It Happening Next Time
Every brewer eventually stares down a silent airlock, an off smell, or a beer that just tastes wrong. Most of those batches are not ruined, and almost every fault carries a lesson that makes the next brew cleaner. This guide treats each problem the way an experienced brewer would at your side: what actually went wrong, how to read the warning signs, what it does to the finished beer, how to fix it now, and how to prevent it entirely.
The advice scales across methods. Where a step changes for can-and-kit brewing, extract, partial mash or all-grain, it is called out inside the card. If you are new to the process, the complete kit brewer's handbook covers the fundamentals this guide assumes.
How to use this page: jump to your symptom below. Each card runs in the same order: quick diagnosis, why it happens, how to fix it, how to prevent it, and when to save or bin the batch, so you can act fast and understand what you are doing.
Airlock won't bubble · Fermentation stalled · Beer tastes sour · Is it infected? · Cloudy / hazy beer · Off-flavour decoder · Hot / solventy alcohol · Plastic / medicinal taste · Too sweet · Missed target gravity · No head / poor foam · Harsh / astringent · Boil-over · Flat bottles · Gushers & bottle bombs
Fermentation won't start or stalls partway
Why isn't my airlock bubbling?
Twenty-four to forty-eight hours in, the airlock sits silent and doubt creeps in. Here is the reassurance up front: a quiet airlock is not proof of a failed fermentation. An airlock is a pressure-relief valve, not a fermentation gauge.
- Press gently on the lid. If airlock fluid moves, the vessel holds pressure; gas is escaping somewhere else, not that it isn't being made.
- Shine a torch through the side. A ring of foam (krausen) on top means fermentation is running.
- Take a hydrometer reading. If gravity has dropped below your original gravity (OG), you are fermenting. Full stop. This is the only definitive test.
Yeast converts sugar into roughly equal parts ethanol and CO₂. That CO₂ leaves by the path of least resistance. A lid that isn't fully clipped, a dry or ill-fitting grommet, or a bucket seal that has perished all let gas slip out silently, so the airlock never bubbles even though the beer is fermenting normally.
The genuine no-start causes are narrower: yeast that was dead on arrival (old, heat-damaged, or a starter that never took off), wort pitched too cold for the strain, or a badly under-pitched batch that is simply slow to get going.
- Re-seat the lid and airlock. A smear of food-grade glycerol or keg lube on the grommet and O-ring restores the seal without contaminating anything.
- Check temperature at the beer, not the room. Bring an ale into its strain's range, typically 18–22°C (64–72°F), because a fermenter can sit several degrees cooler than the air around it.
- Give it time and one gravity check per day. If there is still no krausen and no gravity drop after 72 hours, pitch a fresh, healthy sachet. A packet of dry US-05 rehydrated first is the most reliable rescue.
By method: kit and extract brewers usually get a generous, fresh sachet under the lid. Sprinkle-pitching is fine above ~20°C, but rehydrating dry yeast first noticeably shortens lag. All-grain and high-gravity brewers should oxygenate the chilled wort and pitch enough cells; a single sachet under-pitches anything above about 1.055.
Before you panic over a quiet airlock again, learn to read the batch instead of the bubbles: how to tell whether your beer has actually fermented walks through the gravity-based checks that make the airlock irrelevant.
My fermentation started well, then stopped short
Fermentation runs vigorously for two or three days, then goes quiet while the hydrometer remains well above your expected final gravity (FG). A true stuck fermentation leaves residual sugar the yeast should have eaten, giving a sweet, under-attenuated, often lower-alcohol beer that can also over-carbonate later if you bottle it.
Take a reading, wait 48 hours at fermentation temperature, and read again. Identical readings two or three days apart, still above target, is a real stall. A single high reading is not; the beer may simply be slow. Always compare against the recipe's expected FG, not against zero.
- A temperature drop. The single most common trigger. A cold snap makes yeast flocculate (clump and settle) early, especially clean ale strains and lager yeast.
- Under-pitching or unhealthy yeast. Too few cells for the gravity, or tired harvested yeast, run out of steam before the job is done.
- Low oxygen or nutrient at pitch. Yeast needs dissolved O₂ to build healthy cell walls; extract and adjunct-heavy worts can be low in the free amino nitrogen (FAN) yeast needs.
- Very high gravity. Big beers stress yeast and finish slowly; some strains quit around 8–10% ABV.
- Rouse the yeast. Swirl the fermenter to lift settled yeast back into suspension. Do it gently; you want to resuspend cells, not splash oxygen into finished beer.
- Warm it up. Raise the beer 2–3°C into the top of the strain's range, e.g. 20–22°C (68–72°F) for most ales. Warmth alone restarts many stalls within a day.
- Then re-pitch if needed. Still stuck after 48 hours warm? Pitch an actively fermenting starter of a vigorous strain (US-05 is the workhorse) so it goes straight to work rather than lagging.
Yeast nutrient helps prevent a repeat but rarely restarts a stall on its own; proactive fermentation management shows how to head this off before it starts.
Pitch enough healthy cells, get oxygen into cool wort before pitching, and hold a steady temperature rather than letting the garage swing overnight. Yeast that starts strong finishes strong: the oxygen, sterol and zinc that build healthy yeast cell walls are what let a fermentation run all the way to FG without help.
Sourness, haze and the signs of infection
My homebrew tastes sour and I didn't mean it to
A sharp, acidic tang (think vinegar, lemon or plain yogurt) in a beer that was never meant to be tart. That acidity comes from bacteria or wild yeast producing lactic or acetic acid from sugars they were never supposed to reach. It is delicious in a deliberately soured ale; in a pale ale or lager it is a contamination.
- Taste it cold. Chilling suppresses perceived acidity, so judge it near serving temperature, not warm from the fermenter.
- Look at the surface. A skin, a wrinkled film (pellicle), oily slick or vinegar smell points to live spoilage organisms.
- Vinegary (acetic) usually means oxygen plus Acetobacter; tart-and-clean (lactic) points to Lactobacillus or Pediococcus.
Almost always post-boil, when the beer is no longer sterile: a scratched fermenter or bottling bucket, a cracked tap, tired vinyl tubing, an under-sanitised bottling wand, or air drawn across warm beer during a splashy transfer. Acetobacter in particular needs oxygen, which is why sloppy racking and half-empty vessels breed it.
Safety: do not bottle a sour beer that is still sweet. Wild bugs keep eating sugars in the bottle and can build pressure until glass fails. If in doubt, keg and refrigerate, or dispose of it.
Sanitation is the whole game after the boil. Retire any plastic that is scratched or cloudy, replace old tubing, and sanitise everything the cooled wort or beer touches. If your batches keep souring, the culprit is usually a hidden biofilm. The guide to why sanitisation quietly fails explains why cleaning and sanitising are two separate steps, and why you can't sanitise a dirty surface.
Is that growth on top an infection or just krausen?
Normal krausen is a rocky, tan-to-cream foam that rises during active fermentation and falls back within days. What worries brewers is anything that appears after fermentation, looks structured or fuzzy, or shows unusual colour. Use the look to tell friend from foe.
| What you see | Likely cause | Verdict |
|---|---|---|
| Pellicle: chalky, wrinkled, bubbled skin across the surface | Brettanomyces or bacteria | Infected. Taste it; drink if clean and pleasant, otherwise dump. |
| Mould: fuzzy blue, green, black or white spots standing above the liquid | Airborne mould on low-alcohol or exposed beer | Dump it. Not worth the health risk. |
| Ropey / oily strands: beer pours thick or slimy | Often Pediococcus (a "sick" phase) | Infected. Only worth keeping in a deliberate sour programme. |
Colour and texture identify the organism; only taste and smell decide whether a non-mould batch is drinkable. A thin pellicle on an otherwise clean-tasting beer can be perfectly fine to drink young; if you want a fuller diagnostic, how to tell if your beer is infected runs through the signs. Mould is the exception; there is no salvaging it.
Two levers: sanitation and oxygen. Keep post-boil surfaces spotless, and keep headspace and splashing to a minimum, because warm beer plus oxygen is exactly what the wrong microbes want. The same discipline that prevents infection also prevents most off-flavours and stray smells; they share a root cause.
My beer is cloudy and won't clear
Haze is cosmetic far more often than it is a fault, but it tells you something about the batch. The fix depends entirely on which haze you have, so identify it before you reach for finings.
Chill a glass to fridge temperature. If it hazes when cold and clears as it warms, that is chill haze: proteins and polyphenols linking up in the cold, harmless and temporary. If it stays cloudy at every temperature, you are looking at suspended yeast, or (for all-grain) starch haze.
- Yeast in suspension: still cloudy warm, most common in young beer or with low-flocculating strains. Time and cold fix it.
- Chill haze: protein-polyphenol complexes; clear warm, hazy cold. A vigorous rolling boil and a fast chill to form a good cold break reduce it at the source.
- Starch haze (all-grain): a permanent milky haze from an incomplete mash conversion. Confirm conversion with an iodine test next time; see diagnosing starch haze and low mash efficiency.
- Give it time and cold. Most young beer brightens on its own. Cold-crashing at 0–4°C (32–39°F) for 2–3 days drops yeast and haze out hard.
- Add a kettle fining. A Whirlfloc or Irish moss tablet in the last 10–15 minutes of the boil helps proteins clump and settle.
- Use a cold-side fining if needed. Gelatin works best on beer chilled below 10°C (50°F), and as close to 0°C as you can manage; it binds chill-haze proteins and yeast and drags them to the bottom in a day or two.
By method: kit and extract beers rarely have starch haze: theirs is nearly always yeast or chill haze, so cold-conditioning alone usually does it. Only all-grain batches get starch haze, and there the fix is on brew day, not in the glass. A full walkthrough lives in clearing beer and removing unwanted haze.
Off-flavours and aromas: reading the signals
The off-flavour decoder: name it, trace it, fix it
The beer looks fine but something is off: butter, cooked corn, green apple, wet cardboard. Each of these maps to a specific cause in your process. Find the taste, read across to the cause, and fix it at the source rather than chasing it downstream.
| Tastes / smells like | Compound | Cause → fix |
|---|---|---|
| Green apple, wet latex paint | Acetaldehyde | Beer pulled off the yeast too early. Fix: leave it on the yeast another week at 20–21°C (68–70°F) to let it re-absorb. |
| Movie-popcorn butter, butterscotch, slick mouthfeel | Diacetyl | Yeast stressed or rushed. Fix: a "diacetyl rest": raise to 20–22°C (68–72°F) for 2–3 days at the end of fermentation before crashing. |
| Cooked corn, canned cabbage, tomato | DMS | Precursors not boiled off, or slow chilling. Fix: a vigorous, uncovered rolling boil of 60+ minutes, then chill fast. |
| Struck match, rotten egg (fades with time) | Sulphur (H₂S) | Normal from lager yeast and young beer. Fix: usually just time; it vents with conditioning. Persistent sulphur can signal stressed yeast. |
| Wet cardboard, stale paper, sherry | Oxidation | Oxygen on finished beer. Not reversible: prevent with gentle transfers and minimal headspace; see managing your oxygen budget. |
| Solventy, hot, boozy (see full card below) | Fusel alcohols | Fermented too warm / under-pitched. Fix: control temperature next time; details here. |
| Plastic, sticking-plaster, clove, TCP | Chlorophenols / phenols | Chlorine in water, wild yeast, or un-rinsed sanitiser. Fix: treat your water; details here. |
One perception trap worth knowing: dry-hopping lifts aroma, which can make a beer seem drier or less sweet, but it adds no bitterness (IBUs) and fixes no fault. Chase the root cause first, then adjust hops for balance. The full library of causes and prevention is in identifying off-flavours and smells in homebrew.
Pitch enough healthy yeast; hold fermentation temperature steady in range; boil hard and chill fast; and keep oxygen away from finished beer. Stale ingredients cause their own faults; cheesy, oxidised hops are a common one, so store your hops, grain and yeast properly between brews.
My beer tastes hot, boozy or solventy
A burning, spirituous, nail-polish edge that reads as "stronger than it is" and can leave a next-day headache out of proportion to the ABV. That is fusel alcohol: heavier alcohols the yeast throws off when it is pushed too hard.
Fusels form when yeast is overworked early in fermentation: too warm, too much sugar, or too few cells for the job. Heat is the biggest driver: the first 72 hours set the flavour, and a fermenter that free-rises into the high 20s°C during the vigorous phase is the classic cause. High-gravity worts and under-pitching pile on the stress.
Keep ales in the 18–20°C (64–68°F) band during the first few days and pitch a healthy, adequate amount of yeast. Because fermentation is exothermic, the beer runs warmer than the room; aim your thermostat at the beer, not the air.
By method: kit brewers often ferment in a warm cupboard or hot-water-cylinder space; move the fermenter somewhere cooler and more stable, or sit it in a tub of water to buffer temperature swings. All-grain and high-OG brewers should pitch a starter or extra sachet. The full playbook is in preventing fusel alcohols in your homebrew.
My beer tastes of plastic, sticking-plaster or medicine
A sharp, artificial note (TCP, band-aid, savoury clove) that clings to the finish. These are chlorophenols, and they are potent: a tiny amount of chlorine reacting with natural phenols in your beer produces a flavour you can detect at parts per billion.
- Chlorinated tap water. Chlorine or chloramine straight from the mains reacts with malt phenols. The most common cause by far.
- Un-rinsed sanitiser. Bleach-based or chlorine sanitisers left on equipment carry straight into the beer.
- Wild yeast. A Brettanomyces or wild strain can also throw medicinal phenols; suspect this if you also see infection signs.
Treat your brewing water. Half a crushed Campden (potassium metabisulphite) tablet treats about 40–75 litres and neutralises both chlorine and chloramine instantly; stir it in and wait a few minutes before brewing. A carbon filter removes chlorine (though not chloramine as reliably), and a 24-hour stand only off-gasses chlorine, not chloramine. Switch chlorine-based sanitisers for a no-rinse sanitiser and you remove the second source entirely.
By method: this bites kit and extract brewers just as hard as all-grain; anyone topping up a fermenter straight from a chlorinated tap is exposed, so treat the water even for a simple can kit. If you want to understand what else your water is doing to the beer, start with the foundations of brewing water chemistry.
Already in the beer? Chlorophenols do not fade out. A very faint case may become more tolerable with time, but a clear plastic/TCP flavour cannot be removed; fix the water and sanitiser routine for the next batch.
Body, balance and gravity
My finished beer is too sweet or cloying
It drinks heavy and syrupy, like flat cordial or unfermented wort, with no crisp finish. Residual sweetness is unfermented sugar, and there are two very different reasons it is still there, needing two different responses.
Check final gravity against the recipe. FG well above target means fermentation stalled or is unfinished; treat it as a stuck fermentation and get the yeast working again. FG on target but the beer still tastes sweet means the wort was built with too many unfermentable sugars, which is a recipe and process issue, not a yeast problem.
For all-grain and partial mash, mash temperature sets fermentability. Mash hot (above ~69°C / 156°F) and beta-amylase denatures quickly, leaving long, unfermentable dextrins and a full, sweet body. Mash cool and you get a drier beer. For kits and extract, over-sweetness usually comes from priming the ferment with too much malt/dextrose blend, or a kit that is simply formulated sweet.
If it's finished but too sweet: you can't strip out dextrins, but you can rebalance. Increase bitterness or dry-hop aroma to offset the sweetness, or blend with a drier beer. As a last resort, pitching a more attenuative or wine/champagne yeast can dry it a little further, but expect a thinner result.
If it's stalled: rouse and warm the yeast first, exactly as in the stuck-fermentation card.
| You want | Mash at | Result |
|---|---|---|
| A drier, crisper beer | 64–66°C (147–151°F) | More fermentable sugar, thinner body, higher attenuation |
| A fuller, maltier beer | 68–69°C (154–156°F) | More dextrins, rounder body, more residual sweetness |
This is the enzyme balance at work: see why mash temperature dictates your beer's destiny and the alpha vs beta amylase breakdown. Kit brewers get the same lever by swapping some brewing sugar for a less-fermentable malt extract, or the reverse for a drier finish.
I missed my target original gravity
Your OG reads noticeably above or below the recipe. Gravity tracks dissolved sugar, so a miss means either your sugar extraction was off or your volume was wrong. That difference directly affects final alcohol and balance. The good news: OG is one of the easiest faults to correct on the day.
- Stir the wort thoroughly before sampling; sugar stratifies, and an unstirred sample reads wrong in either direction.
- Temperature-correct the reading. A hydrometer is calibrated to one temperature (usually 20°C / 68°F); a hot sample reads falsely low.
- Check your volume against the fermenter's marks; being 1–2 litres out moves gravity more than most brewers expect.
If your numbers still won't behave, why your hydrometer reading keeps changing covers the sampling and calibration traps in detail.
- Still pre-boil: extend the boil to drive off water and concentrate the sugars.
- Post-boil: stir in dry malt extract (DME). As a rule of thumb, ~100 g of DME lifts 20 L by about 0.002 (2 gravity points); for a 23 L batch, roughly 115–120 g moves OG ~0.002. Dissolve it in a little hot wort first to avoid clumps.
- Kit & extract: the same DME trick applies; keep a bag on hand to top up a thin batch.
Dilute with clean, boiled-and-cooled (or filtered) water to hit target. The quick maths: current gravity points × current volume ÷ target gravity points = the volume you need. For example, 1.060 wort (60 points) at 20 L, aiming for 1.050 (50 points): 60 × 20 ÷ 50 = 24 L, so add ~4 L of water.
For all-grain, most misses are efficiency: check your crush (finer, without shredding husks), mash temperature and mash-day efficiency, and measure pre-boil gravity so you can correct before the boil rather than after. Measure volumes precisely every time; gravity is only as good as your litres.
My beer has no head, or the foam vanishes instantly
The beer is carbonated (it hisses and fizzes), but the foam collapses in seconds and leaves no lacing. Carbonation and head retention are different things: one is dissolved CO₂, the other is whether proteins can hold that gas in a stable foam. Poor retention is almost always a contamination of the beer's surface chemistry.
- Fat, oil or detergent film on the glass or in the fermenter/bottles. Even a trace of dishwashing residue or lip-balm on the rim flattens foam instantly, making this the number-one cause.
- Too many light adjuncts. A grist heavy in sugar, corn or rice thins the foam-positive protein.
- Over-fining. Aggressive gelatin or filtration can strip foam proteins along with the haze.
- Test the glass, not the beer. Pour into a fresh "beer-clean" glass, rinsed of all detergent, no oily residue. If the head holds, your glassware was the culprit.
- Rinse detergent, don't scrub oils in. Avoid greasy sponges on fermenters and bottles; a caustic clean-and-sanitise routine for your fermenter removes films that hand-washing leaves behind.
- Adjust the recipe. Add 5–10% wheat or a small amount of carapils/dextrin malt (all-grain and partial mash) to boost foam-stabilising protein.
By method: kit and extract brewers can't change the mash, so the wins are clean glassware, clean packaging gear, and a kit with some wheat or dextrin in it. Water balance matters too; higher chloride tips the mouthfeel and head fuller, as covered in how calcium, sodium, sulfate and chloride build mouthfeel.
My beer is harsh, drying or puckering
Not sour and not bitter, but a rough, mouth-drying, tea-like or grape-skin astringency that grips the sides of your tongue and lingers. That is tannin (polyphenol) extracted from grain husks or, in kit brewing, from over-steeped specialty grains. It is one of the most method-dependent faults there is.
- Sparge water too hot or mash pH too high. Above ~78°C (172°F), or with high-pH water, husks give up harsh tannins.
- Over-sparging: rinsing the grain bed too far, past the point where sugars run thin and tannins run free.
- Steeping grains too hot or too long (kit/extract), or boiling the grains: a very common beginner cause.
- Squeezing the grain bag and over-crushed, shredded husks both add to it.
Already astringent? There's no removing tannin. A light case softens a little with a few weeks' conditioning and can be partly masked by malt sweetness or a fuller carbonation, but a strongly astringent beer won't come right; log the cause and correct the process.
Kit & extract: steep specialty grains like tea: hold below 70°C (158°F) for no more than 20–30 minutes, lift the grains out before the boil, and never boil them. Don't squeeze the bag.
Partial mash & all-grain: keep sparge water at or below 76°C (168°F), stop collecting when runnings drop toward 1.008–1.010, and hold mash pH in the 5.2–5.6 range. If your water is very alkaline, treat it; the water chemistry foundations show how.
Brew-day mishaps
The kettle is about to boil over
Foam surges up the sides just as the wort reaches a boil and threatens a scalding, sticky mess across the stovetop. It happens fast because it is a physical event, not a slow build, so the response has to be immediate.
- Cut the heat immediately. This is the fastest single move.
- Stir hard to collapse the foam.
- Mist the surface with cold water from a clean spray bottle to knock the foam down.
As wort approaches boiling, "hot break" proteins and released CO₂ form a foam matrix that traps steam. The moment the boil breaks through, that matrix swells and climbs the kettle wall in seconds. The hop-oil and protein content of wort makes it far more foam-prone than plain water, which is why it always seems to happen the instant you turn your back.
Safety: boiling wort is sticky, slippery and scalds badly. Kill the burner before you clean up, and never stand over a full kettle on a wet floor.
Use a kettle at least twice your batch volume for headroom, and never fully cover the pot at the boil. Watch closely through the "hot break": the first few minutes are the danger window. A drop of Fermcap-S in the kettle suppresses foam reliably if boil-overs are a recurring problem. Once the boil is safely underway, plan your fast wort-chilling for the end; a quick chill protects flavour and clarity.
Packaging and carbonation
My bottled beer is flat
You crack a bottle and get no hiss, no head, and a thin, lifeless mouthfeel. Bottle conditioning is a small second fermentation: priming sugar plus the yeast still in suspension produces CO₂ that dissolves into the beer under pressure. Flat beer means that mini-ferment didn't happen, and it usually just needs the right conditions to get going.
- Warm the bottles to 20–21°C (68–70°F) and give them a full three weeks. Cold storage stalls conditioning; most "flat" beer is simply too young or too cold.
- Invert each bottle once, gently, to rouse settled yeast. Don't shake; you don't want to oxidise it.
- Too cold or too soon: conditioning barely moves below ~18°C.
- No priming sugar, or too little: no fuel, no CO₂.
- Caps not sealing: worn crown seals or a mis-set capper let gas escape.
- Yeast too tired: a long, cold-crashed or very high-ABV beer may lack viable cells to carbonate.
If it is still flat after three warm weeks and caps are sound, the yeast has likely dropped out. You can re-prime: uncap, add a few grains of fresh dry yeast (rehydrated) to each bottle, re-cap with fresh crowns, and condition warm again.
Prevent it by confirming fermentation is truly finished (stable FG for 2–3 days) before bottling, and by dosing sugar accurately; use a priming sugar calculator and aim for the right CO₂ volumes for the style. The general carbonation guide and the bottle conditioning walkthrough cover the numbers and the timing.
My bottles gush, over-foam or feel over-pressured
Open a bottle and it erupts; pours are all foam; caps bulge. Over-carbonation is the opposite of flat beer, and it is the one fault on this page with a genuine safety edge: excess pressure can burst glass. Treat gushers as a warning, not a quirk.
Bottle-bomb safety first. If bottles are gushing or caps bulging, move them carefully into a fridge to slow the pressure, and stand them inside a sealed tub or heavy box. Chill for 24–48 hours before opening, open slowly behind a cloth or closed door, and never store suspect bottles somewhere they could hurt someone if they fail. Warm, over-primed bottles are the ones that let go.
- Bottled before fermentation finished. The most common and most dangerous: residual sugar plus priming sugar makes far more CO₂ than intended. This is why a stable FG matters.
- Too much priming sugar, or sugar unevenly mixed so some bottles get a double dose.
- A wild/infection bug eating sugars the yeast left behind; suspect this if gushing worsens over weeks or the beer also turns sour.
Bottle only when gravity has held steady for 2–3 days; confirm with the same is-it-finished checks used for a stuck ferment. Measure priming sugar with a calculator based on the beer's warmest post-ferment temperature, mix it evenly through the whole batch in a bottling bucket rather than dosing bottles by eye, and keep sanitation tight so no wild bug is left to over-carbonate for you. For the full packaging-hygiene angle, see the dedicated guide to preventing gushers.
Brew it well, then brew it the same way twice
Nearly every fault above traces back to one of five variables: sanitation, yeast health, temperature, oxygen and measurement. Get those under control and the problems on this page mostly stop appearing. The difference between a lucky batch and a good brewery is a logbook: write down your gravities, temperatures and timings so that when something changes, you can see what and why. Monitoring fermentation with gravity and temperature data and the broader approach to brewing consistently well are the natural next steps once you've fixed the fault in front of you.
- A quiet airlock proves nothing. Trust the hydrometer, not the bubbles.
- Most stalls are cold stalls. Rouse the yeast and warm the beer before you re-pitch.
- Sanitation and oxygen control prevent the sour, infected and oxidised faults you can't reverse.
- Temperature in the first 72 hours decides fusels, diacetyl and off-flavours; aim your thermostat at the beer.
- Treat your water for chlorine, and steep grains gently, to avoid plastic and astringent flavours.
- Never bottle a beer that isn't finished. A stable FG for 2–3 days is what stands between you and gushers or bottle bombs.
- Dextrins, oxidation, fusels, tannins and chlorophenols can't be removed; everything else on this page is fixable if you catch it early.
Brewing is a craft of small variables and calm decisions. Bookmark this page, keep notes on every batch, and share the direct link to any card above when a mate hits the same wall. Fix what you can, learn from what you can't, and brew again.
