I'll try to be quick and as detailed as I can be: Wednesday I did a small batch, 1 gallon extract stout which ended up with an OG of 1.082. I pitched a full vial of WLP 004 and fermentation started at some point Thursday morning. Thursday I did a small 1 gallon BIAB stout and ended up with an OG of 1.086. While I was brewing that, I bottled a 1 gallon red ale that had an OG of 1.064 with a full vial of WLP 004 and finished at 1.010 in a duration of 7 days. I decided to to just rack the BIAB on top of the red ale yeast cake in which fermentation started a couple hours after that. Friday I wake up to both of them bubbling nearly equally at a two to three bubbles a second in the blow off but by the end of the day, the BIAB that I put on the existing yeast cake had slowed down to about a bubble every 6 seconds while the first stout is still at about 1 bubble a second. I realize I am probably pitching to much yeast to begin with but I wasn't sure given the gravity's are a bit higher. My question is it possible that the existing yeast cake may not be able to handle the second beer? And at one point do I try to remedy it? I am assuming if fermentation completely stops I can just pitch a small amount of yeast, just wanted to be sure thats what I should do.
RDWHAHB. Don't make any decisions based on airlock/blowoff activity alone. Gravity readings are your friend here. It's likely that the beer on the existing yeast cake is reaching terminal gravity sooner than the vial due to the higher pitch rate.
You overpitched. It's not ideal, and it's not as bad as underpitching. Don't try to fix it. You'll have a good beer in the end. BTW, stop counting bubbles and get the hydrometer ready in 3 weeks.
The conventional wisdom holds pitching on a yeast cake following an 86 OG batch is not a good idea b/c the yeast are too stressed by the high ABV.
