Refermentation Method 1
In order to restart fermentation, make sure it is to be conducted at the recommended temperature of 25C 77F.
Dissolve 5 ml (1 teaspoon) of sugar in half a cup of lukewarm water (35-40C), add the yeast, stir and leave covered for 15 minutes. When vigorously fermenting, add 125 ml (quarter pint) of wine. When this is
vigorously fermenting add another 250 ml (half pint) of your wine. Once this has started to ferment, add the remainder of your wine 500 ml (1 pint) at a time, always allowing each stage to be in vigorous
fermentation before adding the next.
Maintaining the above recommended temperature and stirring the jar daily, to keep the yeast in suspension, should allow you to ferment out your wine satisfactorily
Refermentation Method 2
This method is sometimes in removing or reducing any off-flavours.
Make up a starter by dissolving 5 ml (1 teaspoon) of sugar in half a cup of lukewarm water (35-40C), add the yeast, stir and leave covered for 15 minutes.
To each gallon of wine add 4oz sugar and 1 pint water. When the starter is fermenting, add 125 ml (quarter pint) of your sweetened diluted wine and put back in a warm place. Thereafter add
500 ml (1 pint) your wine each time the starter shows signs of fermentation, and allow to ferment to dryness. Add campden tablets and fine the wine in the usual way before tasting to assess whether the cure has
worked. Although the wine should be kept warm while refermentation is in process, take care! Too much heat may have caused the problem you are trying to cure.