A stuck fermentation has stopped before all fermentable sugar is consumed — leaving the wine sweet when you intended dry, or at risk of refermentation in bottle.

Common causes

Nutrient deficiency (insufficient YAN)
Temperature shock — too cold or too hot
High initial sugar (OG >1.130) stressing the yeast
High alcohol inhibiting the yeast
Too much SO₂ at the start

Restarting

Warm the wine to 20–22°C
Add Fermaid-K or a rehydration nutrient
Prepare a yeast starter with K1V-1116 or EC-1118
Gradually step the starter into the stuck wine over 24–48h to acclimatise it to the alcohol level

⚠️ Never add dry yeast directly to a stuck, high-alcohol wine — the osmotic shock will kill the yeast instantly. Always rehydrate and acclimatise with a starter.

Stuck Fermentation

Common causes

Restarting