It normally takes between two to three weeks for grapes to fully ferment into wine after being crushed. The fermentation occurs in two stages, primary and secondary fermentation.
In general, primary fermentation usually lasts about three to seven days. Primary fermentation requires air to help the yeast cells multiply, after which they consume sugars in the grape juice and turn them into wine. Approximately 70 percent of the total alcohol content is created during primary fermentation.
Secondary fermentation usually lasts between one to two weeks depending on the amount of sugar left in the liquid. This process is anaerobic, meaning it is done without the presence of air. By eliminating the air, it signals the yeast to stop multiplying and focus solely on converting the remaining sugars into alcohol.