Weight of one gallon of alcohol?

Almost the same as pure water The specific gravity of fermented wine is very close to that of water, because although the weight is increased by dissolved solids, it is reduced by the alcohol content.

Sweet wines tend to have a higher SG, so they weigh a bit more per gallon than water, which weighs 8.34 pounds per US gallon. During the winemaking process, it can weigh as much as 9 pounds or more.