Common Winemaking Problems and How to Fix Them

Even experienced winemakers run into problems. The good news is that most issues are diagnosable and fixable — often the wine is perfectly salvageable with the right intervention.

Smells Like Vinegar

Cause: Acetobacter bacteria have turned your alcohol into acetic acid. This is usually caused by too much oxygen exposure (leaving the demijohn headspace too large, poor airlock maintenance, or using contaminated equipment).

Fix: Unfortunately, once a wine has turned significantly vinegary, it cannot be reversed. Make vinegar from it (genuinely useful!) or discard. Prevention is everything — always keep your demijohn topped up, keep the airlock filled, and sterilise all equipment.

Sulphur / Rotten Egg Smell

Cause: Stressed yeast producing hydrogen sulphide. Usually caused by yeast nutrient deficiency, very low pH, or yeast under temperature stress.

Fix: Add a teaspoon of yeast nutrient and stir vigorously. Splash racking (pouring from height) can help dissipate the gas. Often resolves itself as fermentation completes.

If the smell is more like a struck match than rotten eggs, you've added too many Campden tablets. Splash rack and leave in a warm place — it should dissipate within a week.

Mouse Cage Smell

Cause: A rare but very unpleasant infection by Brettanomyces yeast or certain bacteria. More common in wines that haven't been protected with Campden tablets.

Fix: Cannot be reversed. Prevention is everything — sterilise thoroughly, use Campden tablets, and keep headspace minimal.

Wine Won't Clear

Cause: Pectin haze (from fruit), protein haze, or yeast still in suspension.

Fix: See our full guide on Clearing and Fining. In summary: add pectolase (if you didn't at the start), try bentonite for protein haze, and give it more time somewhere cool.

Wine is Too Sweet / Won't Ferment Dry

Cause: Fermentation stuck before completion. Usually temperature, nutrient, or pH related.

Fix: See our full guide on Stuck Fermentation. Try warming, adding nutrient, and repitching with EC-1118 yeast.

Wine Tastes Flat or Thin

Cause: Insufficient body. Common in flower wines or those made from low-tannin, low-acid fruits.

Fix: For future batches, add grape tannin (half a teaspoon per gallon), raisins or sultanas (adds body and nutrients), or grape juice concentrate. For the current batch, blending with a fuller-bodied wine can help.

Wine is Too Acidic / Tart

Cause: Too much acid blend added, or naturally acidic fruit (blackcurrant, gooseberry).

Fix: Add precipitated chalk (calcium carbonate) at 1g per litre, stir well, and leave for 24 hours. Alternatively, blend with a lower-acid wine. For future batches, add less acid.

Sediment in Bottled Wine

Cause: Wine was bottled before fully stable, or not racked enough times.

Fix: Nothing to do now except warn people. The sediment is harmless — stand the bottle upright for 24 hours before opening to let it settle to the bottom, then pour carefully. Decant if needed.

Wine Re-fermenting in the Bottle

Cause: Wine was bottled too early, or potassium sorbate wasn't used when sweetening.

Fix: Immediately transfer back to a demijohn — carefully. Check all corks and seals. Add Campden tablets and potassium sorbate, leave to fully stabilise, then rebottle. Always use potassium sorbate when back-sweetening before bottling.

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