I brewed up a Barleywine this past weekend that clocked in at 1.117. Had 6 gallons of wort and pitched two packs of Nottingham. Set up a blow off tube and that yeast took off. Today, 5 days after pitching, it is down to 1.039 (10% ABV) and still has a little time to go.
I lost about a gallon of wort through the blowoff tube and I have about just under a half gallon of trub in the fermenter. This will leave me about 4-1/2 plus gallons of beer to bottle.
My question is, for large gravity beers like this, has anyone split the batch into two separate fermenters so that there was more room for the krausen and less opportunity for loss? Figuring I might try this and then combine the two into a purged and CO2 filled keg for secondary so they two ‘batches’ could mix and mingle.
Anyone have experience with doing something like this?
I’ve done what you are suggesting, but for a different reason. I wanted to dry hop a hazy ipa with 10 ozs of hops. The reason for splitting was to start with a higher than normal (for me) volume of wort. I put 7 gallons into two fermenters and brought some trub with it. With the loss after dry hopping, I still had a decently full keg and a lot of sludge left in the fermenters.
I tend to put half the hops in just as fermentation is slowing and having extra space in the fermenter helps with the height of krausen that sometimes follows.
I used to brew a lot of one gallon batches in 4l wine jugs which inevitably ended up the same way with a comparably large volume of trub and a beer or so in blowoff. A couple things helped me with this issue that might be useful to you.
Reduce the sediment in the wort before pitching. Look at how you might be able to reduce sediment going into the kettle and then into the FV. Recirculating mashes can really help with this. If an option, rack the wort into one vessel, chill and let sediment drop and then rack into your FV and pitch.
A small amount of fermcap in the fermenter will help reduce explosive krausen which will reduce your blowoff loss. Be gentle with application because too much will ruin head retention in the beer. A drop or two at pitching should be enough. If you’re still getting wild krausen, add another drop until it gets under control.
Ultimately, yes, splitting the batch and giving yourself more headroom will help solve blowoff losses if you have the equipment for it. If you’re going to rack the two batches together into one vessel, consider doing so as fermentation winds down so the yeast can uptake any oxygen dissolved into the beer during the racking process.