This is my first year making our own wine. I followed the recipe of 1 qt fruit (we used our grapes), 1pkg yeast, 2cups sugar, 1 gallon water. Mashed the grapes, strained for the juice and bottled in a glass jar for 3 weeks. Strained again, bottled and corked it. Went downstairs last night to put our apples into cold storage only to discover that 4 of the bottles had blown their corks and I had "wine" all over the shelf. No fancy eq. just plain old stuff. What would have caused this? They were all from the second batch which the only difference was the grapes were riper off the vine. I am getting ready to do a third batch and the only difference this time is I am using the wine yeast instead of regular yeast. Have I wasted all my time?