Specific gravity is a measure of how dense a liquid is. In winemaking, specific gravity is used to help determine the alcohol content of a wine (starting specific gravity minus finished specific gravity). It is also used to determine whether or not a wine has finished fermenting. Below, is the hydrometer in a small sample of rhubarb wine.
This particular wine has a beginning specific gravity of 1.070. If you turn the hydrometer, it will give you a potential alcohol content. For the 1.070, the maximum alcohol content is 9%. Of course, this can be changed if more sugar is added throughout the process.
We started three more wines that I told you about last week. We began with a reading of 1.090 for the grape and the apple-raspberry wines. That means the potential alcohol content is 12%. As the wines fermented throughout the week, the specific gravity continued to drop. Finally, when they got to 1.030, it was time to transfer them from the primary to the secondary vessels. When the specific gravity falls below 1.000, it will indicate that the fermentation is complete.
This is the concord grape. It is pretty, but the grapes are made for juice and jelly, not wine. Even when finished, it will taste a lot like grape juice.
I’ve never done this combination of apple and red raspberries before, but I am excited to see how it turns out.
Finally, we did the strawberry rhubarb. Because it was a specific recipe with exact amounts, I didn’t bother checking the specific gravity on it.
I will have to use the vinometer to determine the alcohol content of this one since I didn’t use the hydrometer.