I bottled my first batch of wine, which was made from home grown Concord grapes. The wine had been aging in a class carboy in my basement for 2 years. (Not sure whether letting it sit longer helps, but according to the "Vines to Wines" book, he says it ages better in bulk than in individual bottles).
Anyway, I sweetened about 1/2 the batch with Concord grape juice, and then bottled. I was surprised to see corks popping out after a few weeks, and also tasting one of the bottles, it seems like it became a fizzy wine.
I thought that once the wine reached full alchoholic level, all the yeast died? I guess also, based on what I just read, you have to add Sorbate when bottling to prevent this?