First, I’m curious to know what others do when bottling a blended sour, say some 18 month old and some 6 month old. Do you just prime as usual and assume that the additional co2 from the bugs working continuing to work on the young beer wont be enough to affect carbonation? Do you just prime a little on the low side? Is there a certain gravity that the beer should be at, like under 1.009 or something, that is considered safe for bottling? Do you only use certain bottles, like grolsch or champagne bottles that can handle a higher pressure?
Second, I had the idea- based on something similiar that I’ve seen other do- of taking some sour dregs and adding them to a six-pack’s worth or so of beer when I bottle my regular brews; stouts, reds, browns, etc, with FG’s anywhere from 1.010 to 1.024. Anyone see any carbonation/bottle bomb issues with doing this?
Assuming the old and new beer are relatively close in recipe, I would figure that the FG of the blended beer will be the same as that of the older beer, then take a weighted average of the volumes blended and knowing that carbonation is about three points, figure out how much sugar to add (or not). For example, if the older beer is 1.005 and the new 1.009, then a 50/50 blend will be 1.007 with the potential of two points available for carbing, so you would need to add a third of the usual amount of sugar.
On adding souring bugs to higher-OG beers at bottling - you would be running the risk of bottle bombs for sure, but there’s no reason you can’t try it and keep the bottles in a box while carbing. I would also fill a 1L PET bottle at the same time so you can easily monitor the carb level and as soon as the PET bottle is fully inflated, put the glass bottles in the fridge to inhibit the bugs.
My experience with this is limited. BUT, I plan on bottling my blended sours with a target of 2.0 volumes, with the knowledge that it might turn into 3.0 with additional fermentation.
I have used bottle dregs (that I built up in a blended mini-starter “sour zoo”) along with priming sugar in a 1L growler subset of a regular batch of saison. It came out perfectly-- tart and highly but not over-carbonated. It was dumb luck.
My concern with your process about the soda bottle and chilling the bottles once carbonation has been achieved is that some of the bacteria in a sour will add flavor and sour the beer without adding CO2. In other words, when it’s carbonated, it’s not necessarily “done.” I’d aim for a low level of carbonation and then refine your process over time.
