wine making

[Thomas]

Yes and no.

It is right that it is supposed to take the prescribed number of days but--and a big but--nothing, with regard to fermentation, is exact. Environmental temperature fluctuations, time it took for fermentation to begin, juice nutrition, et al, contribute to the timetable for completion.

The best way to tell if the fermentation is complete is to measure the resulting sugar after the prescribed days. You can do this not with a hydrometer, which is great for measuring juice brix, but horrible at measuring wine (the alcohol changes readings) but with a thing called Clinitest--a tablet that is intended to measure sugar in urine of diabtics. You can also use color chromotagraphy to measure resulting sugar.

Knowing the resulting sugar is the only sure way of knowing when fermentation has completed.