Wine faults: brett, TCA, reduction and VA, spotted blind

"Is my wine corked?" is one of the most-asked questions in wine — and one of the most misunderstood. Real wine faults are specific, identifiable chemical problems, not just "a wine I didn't enjoy." Learning to name them does two things at once: it saves you from drinking (or serving) a flawed bottle, and it sharpens the single most advanced tasting skill there is — telling a genuine fault from a stylistic feature. This guide covers the four faults you'll meet most — corked (TCA), brettanomyces, reduction and volatile acidity — plus the judgment call that separates confident tasters from anxious guessers.

The four faults worth knowing

Most everyday problems come down to four culprits. Each has a recognisable signature:

• Corked (TCA): a musty, damp-cardboard, wet-dog or mouldy-basement smell that mutes the fruit. Caused by the compound TCA, usually from a tainted cork. There's no "blow-off" — it only gets worse, and it makes the wine smell muffled and joyless.
• Brettanomyces ("brett"): a barnyard, sticking-plaster (band-aid), horse-stable or smoked-meat character from a spoilage yeast. At high levels it's clearly a fault; at low levels it divides opinion (more on that below).
• Reduction: struck match, rubber, rotten egg or blocked-drain smells from sulfur compounds when a wine lacks oxygen. Often blows off with air — swirl hard or decant and it can fade, which is a useful diagnostic.
• Volatile acidity (VA): nail-polish remover (acetone), vinegar or a sharp, lifted, "sweet-sour" edge from acetic acid and ethyl acetate. A tiny amount can add lift; too much is a clear flaw.

Naming which of these you're smelling is more precise — and more useful — than a vague "this smells off," in exactly the same way that decoding a wine into individual cues beats a general impression.

A couple of rarer faults are worth a mention so you're not caught out. Oxidation — from too much air exposure or a failed seal — turns a wine flat, nutty and sherry-like, with browning colour and bruised-apple notes; it's the opposite problem to reduction, and unlike reduction it doesn't recover. Light-strike (goût de lumière), from prolonged exposure to fluorescent or sunlight through clear glass, gives a cooked-cabbage or wet-wool smell, most often in sparkling and pale rosé wines. Neither is as common as the big four, but recognising them rounds out your fault vocabulary and stops you misreading an old-tasting wine as simply "past it."

Corked: the most common false alarm

TCA is the fault people fear most and misdiagnose most. The signature is subtractive: rather than adding a loud bad smell, mild TCA strips the fruit and leaves the wine flat, damp and dull, like a wet newspaper. At higher levels the musty, mouldy-cardboard note is obvious. Two things to remember: it's harmless to drink but unpleasant, and it's a bottle-level lottery — the next bottle of the same wine is usually fine. If a wine smells muffled and joyless with a damp-basement edge and no fruit, suspect cork taint before you blame the winemaker.

Reduction vs oak smoke: an easy mix-up

Reduction produces a struck-match or rubbery smokiness that beginners often confuse with the sweet, warm toast-smoke of a barrel. The tells that separate them: reductive smoke is sharp and sulfurous (matchstick, rubber, rotten egg) and often blows off with air; oak smoke is warm and sweet and stays put. Some fine whites even carry a deliberate struck-match reductive note as a stylistic signature. If you're unsure whether a smoky note is a barrel or a fault, this is the same fault-vs-feature discipline covered from the oak side in how to spot new, old and no oak blind — and the give-away is whether swirling makes it fade.

The fault-vs-feature judgment

This is where wine faults get genuinely interesting, and where they overlap with real grape character. The same compound can be a flaw in one wine and a signature in another:

• Brett vs savoury complexity. A gamey, cured-meat, smoky note is a classic descriptor for [Syrah](https://sensium.wine/grapes/syrah) — its "cured meat" and smoke are prized in Northern Rhône styles. A trace of that character reads as complexity; a loud band-aid-and-horse funk reads as brett gone too far. The line is a matter of degree and balance.
• Funk vs fault in delicate reds. [Pinot Noir](https://sensium.wine/grapes/pinot-noir) classically shows forest floor and mushroom — earthy, savoury notes that are a feature, not a fault. Beginners sometimes flag this "funk" as spoilage when it's exactly what the grape is supposed to do.
• VA lift vs volatile fault. A whisper of volatile acidity can lift aromatics and make a wine smell more perfumed; in a high-alcohol, ripe style like [Grenache](https://sensium.wine/grapes/grenache) a little lift is common. Cross the line and it turns to nail polish and vinegar.

The skill isn't just detecting a compound — it's judging whether its level enhances or ruins the wine. That judgment is what exam panels test and what separates a confident taster from a nervous one.

A quick blind fault-check

Fold a fast fault screen into your routine, right after the first sniff and before you commit to an ID:

1. Does the fruit seem muffled and the wine smell damp/musty? Suspect TCA (corked).
2. Barnyard, band-aid or horse? Consider brett — then ask whether it's a trace (complexity) or dominant (fault).
3. Struck match, rubber or rotten egg? Suspect reduction — swirl hard and re-smell; if it fades, it was reductive.
4. Nail polish or vinegar? Consider VA — a hint can be lift, a lot is a fault.

Running this screen deliberately stops a fault from quietly derailing your deduction — a musty corked wine, for instance, will hide the fruit you need to identify the grape. It's the same habit-building discipline behind why blind tasting is a skill, not a talent: a repeatable checklist beats relying on a lucky nose.

When to send a wine back

For everyday drinking, the practical rules are simple. A clearly corked wine is a fair reason to return a bottle in a restaurant — it's a defect, not a preference. Obvious, dominant brett, aggressive VA, or a reductive stink that won't blow off after a few minutes of air are also legitimate grounds. But a faint funk, a touch of lift, or an earthy-savoury note that you simply don't like is usually style, not fault — and worth learning to appreciate rather than reject. Knowing the difference makes you a better customer and a far better taster.

Frequently asked questions

How do I know if my wine is corked?

A corked wine smells musty and damp — wet cardboard, mouldy basement, or wet dog — and its fruit seems muted, flat and joyless. The cause is TCA, a compound usually introduced by a tainted cork, and it never improves with air. It's harmless to drink but unpleasant, and it's specific to that bottle, so another bottle of the same wine is almost always fine. If the wine smells muffled and damp rather than fruity, cork taint is the likely culprit.

What does brett smell like in wine?

Brettanomyces smells of barnyard, horse stable, sticking plaster (band-aid) or smoked, cured meat. At high levels it's considered a fault that masks fruit; at low levels it's controversial, because a trace of that savoury, gamey character overlaps with the prized complexity of grapes like Syrah. Whether it's a flaw or a feature comes down to intensity and balance — a hint can add interest, while a dominant funk is a fault.

Can reduction in wine go away?

Often, yes. Reduction comes from sulfur compounds that build up when a wine lacks oxygen, giving struck-match, rubber or rotten-egg smells. Because these compounds are volatile, vigorous swirling or decanting frequently lets them "blow off," and the wine can clean up within minutes. That's a handy diagnostic: if a sulfurous, matchstick smell fades with air, it was reduction rather than a permanent fault like cork taint.

Train your fault radar

Telling a fault from a feature is one of the most advanced tasting skills — and one of the most trainable. Practise reading savoury, earthy and reductive notes on real wines in Blind, and use the grape dossiers to learn which "funky" notes are genuine grape signatures rather than flaws. Unlimited practice across every device is what a Premium plan unlocks.

Further reading: for reference-grade explanations of wine faults, see the Master of Wine resources at Jancis Robinson.

Want to stop second-guessing "is my wine bad"? Train the fault-vs-feature call in Blind, and unlock unlimited practice with Premium.