The first fermentation usually takes 6 to 8 days at room temperature, when the altar is very bubble less and less, and basically only the colorless grape skins and seeds remain, tasting the wine basically no sweetness, it means that the alcoholic fermentation is completed. The purpose of adding sugar is to increase the sweetness, and the other is to increase the conversion of alcohol, so that the aftertaste will be more powerful, which is based on chemical reaction. The second fermentation usually does not add sugar, plus it is fine, the second fermentation is mainly malic acid - lactic acid fermentation, no longer produce alcohol, so the second fermentation with sugar, is basically to improve the sweetness. The second fermentation is two to three weeks, after the wine is clear, on the line.