Stuck Fermentation

beerstar

The beer has not reached the expected final gravity (i.e. the gravity reading has not changed over a period of 3-4 days but is still too high for bottling or barrelling).

This might be accompanied by no visible signs of continuing fermentation and no bubbles rising through the airlock.

masterbrewer

It might not always be possible to re-start a stuck fermentation, but the
following actions are often successful:

Ensure the temperature of the brew is 18-23°C. Gently stir the brew to
rouse the yeast, using a sterilised stirrer/spoon. This action alone will often
start the yeast working again.

Add a new sachet yeast to the brew. This should first be rehydrated and
activated by mixing the dried yeast into a glass of pre-boiled, lukewarm
water together with a teaspoon of sugar. This should be covered and left in
a warm place until seen to be actively fermenting, before stirring into the
main brew.

Use a good quality brewing yeast designed for all malt recipe brews which is
capable of fermenting out higher or complex sugars.