I'm doing a 10gal batch of Nierra Sevada (from this recipe
) and everything on brew day went smoothly, although I went a little light on mash water because I had to physically move my brew pot and didn't want to kill myself, so I ended with 9.0gal instead of 10gal.
My OG was: 1.044, which is close enough for rock n' roll. I split the batch between 2 6.5gal plastic fermenters, one with 5.25 gals, one with 3.75 gals. Noticing this mistake, I split the yeast (2 packets of rehydrated US-05) and pitched.
The 3.75gal fermenter fermented extremely vigorously and tapped out in 48 hours, and the 5.25gal is still going after 5 days. The gravity of the smaller fermenter was 1.004, so things seem to have gone OK (and it tastes great), but I'm really curious about why given proportionally similar pitch rates the larger fermenter is lagging so much? Is there a way to prevent this in the future?