The time of a vinous fermentation commencing is always uncertain;
it depends much on the quality and quantity of the contents of the
vat, on its local situation, on the season or weather, and most
particularly on the greenness or ripeness of the fruit. To produce a
medium vinous fermentation, the vats and contents ought to be placed
in a temperature from 60 to 70 degrees. And if this is found not to
produce fermentation in a short time, the temperature of the place
must be made warmer, and the vat often stirred with the vat-staff.
The commencement of the vinous fermentation may be known by plunging
the thermometer into the middle of the vat, for a minute, and
when taken out, if a fermentation has commenced, the temperature
of the contents will be higher than at the place where the vats
are situated. When the vinous fermentation begins, it is very
conspicuous, and may be known by its taste, smell, appearance, and
effects. The contents will first gently rise, and swell with a slight
movement and a little hissing. A considerable motion will take place,
and the contents will increase in heat and bulk, while a quantity of
air escapes.
It is impossible to lay down an exact time for a vinous fermentation;
but for eighteen gallons, two or three days are generally sufficient
for white wines; and red wines require a day or two more.