Epic Blow-off

Last weekend I brewed two five gallon batches of Russian Imperial Stout with Jeremy. Both recipes were monster beers (more on that in a future post) with target original gravities over 1.100. The brew day was largely uneventful - no boil overs, no stuck mashes / sparges.

We wrapped up brewing around 5pm, filled up the second better bottle with roughly 5.5 gallons of the bigger of the two beers, oxygenated for 45 seconds off of a disposable tank, and pitched a starter of WLP004 (Irish Ale.)

I mistakenly put the temperature control probe on the other beer, which was slightly lower in starting gravity and pitched with WLP001 (Cal Ale.) The typical blow-off rig I've been using at this point is a drilled universal bung with 5' of 1/2" OD tubing into a growler half-filled with Star San.

It probably should've been cause for alarm when I checked on the batch three or four hours later and the big batch was already showing signs of active fermentation. Alas, I was just excited to see it bubbling away.

This is what I found the next morning when I went to check on it... I don't have the fancy vinyl sticky numbers on the side of the better bottles, but I'm guessing we lost about a gallon of beer out through the blowoff hose. That black pool of liquid the carboys are sitting in is potentially delicious monster stout I had to drain out onto my basement floor. The temperature on the smaller beer was stable at the controlled 68F, but the big one had risen to 72F.

Needless to say, after spending a half an hour cleaning this mess up, I moved the growlers out into buckets outside of the freezer and proceeded to witness still more blow-off.

I've never used the foam control products in a fermentation, but does anyone out there have any suggestions for how to avoid this scenario? My thoughts were to use a bigger diameter blow-off hose, add fermcap, or leave a lot more headspace on a big beer like this one...