This is my first attempt to make sparkling wine on purpose. I added sugar, yeast, and dry pear wine to four champagne bottles about seven months ago and capped them with bottle caps. After six months of lying on one side, I rotated them 180 degrees and was glad to notice that there was yeast sediment in all four bottles.
After a week or so I noticed a damp spot on the shelf right under the cap of one of the bottles. In addition, the air bubble in that bottle was twice the size of the bubble in the other three bottles. I put a small dish under it and a few days later had some pear wine residue. I guess the turning released some bubbles from solution, increasing the pressure and causing the leak.
In any case, I performed surgery to try to save it this evening. I put the leaking bottle into the freezer for two hours. I also put a 12-ounce bottle of excess pear wine in for one hour. I removed the bottles from the freezer and popped the cap; there was minor effervescence but apparently it was cold enough to hold most of the gas in solution. I then topped off with the excess pear wine and re-capped. I put a dish under the cap to see if it starts leaking again. Hopefully, it will be properly sealed now and end up as a good bottle of sparkling wine.
Paul