I've brewed about 50-some batches at this point, and along the way I have stashed some of these beers for extended "aging" just to see how they respond to time. Unfortunately, I haven't had much success with this. I haven't had any bottle bombs or anything, but nearly every one of these beers has been way overcarbed - as in, I have glass that is entirely foam and it will take me 30min to pour the whole bottle out. At first I thought I was using too much priming sugar, but the bottles are fine for the first two months. It's only after 2+ months that they get out of hand.
The strangest circumstance of this happening was with a vanilla imperial stout I bottled last october that I only used .5C of corn sugar for priming. I hammered through most of it before the new year, but wanting to save some, I kept a six pack in our 50deg basement. I figured that would be the perfect temp for storing these long term. But sure enough, last night I cracked one open and it foamed all over the place.
For what it's worth, I always use corn sugar and oxygen barrier caps for 5 gal batches.
Any thoughts? Is it possible that my bottles are consistently getting contaminated during bottling?
Thanks in advance!