The wine has finished it’s secondary fermentation over the last two weeks and is ready for the next process: degassing. If this sounds like something you need after Thanksgiving dinner then you’d be close. All of the fermentation has produced millions of carbon-dioxide bubbles that remain suspended in the wine, and we’ll need to get rid of those to prevent corks from popping out or bottles breaking. The bubbles also help to suspend particles that we are trying to get out of the wine to clarify it. The “Wine Expert” kit we’re using has you mix all the sediment in the carboy back into suspension as you stir very vigorously. I use a special paddle with a long rod that attaches to a power drill. Before stirring I add a couple chemicals: potassium metabisulphite kills off the yeast to stop fermentation but also is a powerful antioxidant that prevents discoloration and spoilage, and potassium sorbate which is basically a preservative. These chemicals stabilize the wine to prevent further fermentation and get rid of harmful acids or bacteria. These are added to water first and then stirred into the wine. By stirring rapidly, all of the gas bubbles are released and the wine foams up just like soda poured into a glass. After stirring for a couple of minutes I add something called isinglass clarifier, which will clump together all of the solids suspended in the wine and make them drop to the bottom of the carboy. Then the wine gets more stirring until all the trapped CO2 bubbles escape.
The last step is to put an airlock on the carboy and wait. It’s fun to watch the wine clear. First it’s all cloudy, then the cloudy layer slowly moves toward the bottom of the carboy over the course of about a week. When it gets to the bottom the wine is almost clear.
After about two weeks the wine is totally clear but still has a nice color. The instructions tell you to bottle it from here but I like to transfer the wine into another container and leave the sediment behind. Next I’ll wait another week for any sediment to settle again before bottling.