How to Spot a Bad Wine is an essential skill for any wine lover. You don’t need to be a sommelier or own a cellar full of vintage bottles to detect the most common flaws. All it takes is knowing the signs, trusting your senses, and remembering that a bad wine doesn’t get a second chance—it doesn’t get drunk.

Wine can go wrong due to winemaking flaws, storage problems, or simply because it’s past its prime. The key is recognizing the signs that something is off. This guide breaks down the most frequent wine faults, how to detect them without hesitation, and what to do when they show up in your glass.

What Is a Faulty Wine?

Not everything unusual in wine is a defect. Sometimes, a wine shows bold or challenging notes that are part of its style. But there’s a clear line between what’s unique and what’s flawed.

A faulty wine is one that has lost its quality due to unnatural causes—contamination, improper storage, excessive oxidation, or technical errors during bottling. The result is a wine that’s unbalanced, unpleasant, and far from what it should be.

Common Wine Faults and How to Detect Them

TCA (Trichloroanisole) or “Cork Taint”

One of the best-known and most dreaded flaws. The infamous “corked wine” is caused by TCA, a chemical compound that contaminates natural cork and, in turn, the wine. While not harmful to health, it completely ruins the experience.

It’s easily spotted if you know what to look for: aromas of wet cardboard, damp basement, old paper, or moldy wood. The wine loses all fruit expression, becomes flat and dull. It’s like the life has been sucked out of it. When this happens, there’s no debate—the bottle should be returned.

Oxidation

Poorly managed oxidation turns a wine into a shadow of its former self. This flaw occurs when wine has had excessive contact with oxygen—due to a dry cork, poor storage, or having been open too long.

The signs are clear: the color darkens more than expected, taking on orange or brown hues. Aromas of bruised apple, stale nuts, or flat cider dominate the nose. On the palate, the wine feels lifeless and stale. A perfect mirror of the air that ruined it.

Volatile Acidity

Nothing smells more out of place in a wine glass than a strong whiff of vinegar or nail polish remover. That’s the telltale sign of volatile acidity, another common defect—especially in poorly stored wines.

Caused by bacteria like Acetobacter, this issue turns alcohol into acetic acid. The result: a wine that stings the nose, feels unbalanced in the mouth, and is better suited for cleaning windows than drinking.

Brettanomyces

“Brett” is one of those flaws that stirs debate. Some believe a tiny bit adds character; others see it as a red flag. It’s a yeast that releases very distinctive aromas when it develops in wine.

Common descriptors include: leather, barnyard, animal sweat, and earthy funk. In small doses, it might lend complexity. But when it dominates and overshadows everything else, it becomes an unforgivable flaw.

Reduction

Reduction is the opposite of oxidation. In this case, the wine has been too deprived of oxygen, generating sulfur compounds that alter its aromatic profile. The result? Smells of rotten eggs, boiled cabbage, or even burnt rubber.

Some mildly reduced wines can recover with aeration, regaining their original aromas. But if the issue persists after a few minutes in the glass—or after decanting—the problem is structural, with no easy fix at home.

Tips to Avoid and Handle Faulty Wines

Avoiding wine faults starts with making informed choices and caring for your bottles:

• Temperature and Storage: Store wine away from heat, direct sunlight, and temperature swings. A constant, moderate temperature is key.
• Check the Vintage: Some wines are made to be enjoyed young. Keeping a light white or rosé for five years is a recipe for disappointment.
• Observe Before Serving: If the cork is dry or hard to remove, there may be issues. Smell the cork, inspect the wine’s color, and sniff the glass—all simple but crucial steps.
• Speak Up in Restaurants or Stores: If you detect a clear flaw, don’t hesitate to report it. Anyone who truly understands wine won’t take offense.
• Avoid Bad Transport Conditions: Leaving a bottle in a hot car trunk over summer can cook it completely—and wine never forgives that.

Spotting a bad wine is a matter of sensory training and learning to read the signs your glass reveals. When something smells like wet cardboard, bruised apple, or an unventilated stable, it’s not terroir speaking—it’s a clear warning that the wine is off.

Learning to detect these faults is part of the journey for anyone who enjoys wine with curiosity and discernment. With these tips, you’ll never again hesitate before taking a sip. Because when wine is good, it’s pure pleasure. But when it’s not… it’s best left behind.