I brewed an Irish stout this weekend and all went well. Vigorous fermentation started in less than 24 hrs. For the first time though, my blowoff container filled and overflowed and I lost about half a gallon of wort through the blow off tube. I'm using a 5 gallon glass carboy with a bung and blow off tube into a vase (approx 1.5 gallon vase filled with 1 gal of sanitized water) This was the highest OG beer that I've done, so that's my initial thought for the loss of wort through the blow off. I also used yeast nutrient for the first time. Recipe below for reference. Is this normal? How can I prevent it on the future? 1.090 OG 1.032 FG 7.7% ABV 9 lbs dark DME 1.5 lbs flakes oats 1 lb chocolate malt .5 lbs roasted barley .5 lbs lactose Omega yeast - Irish stout strand OYL-005 (liquid yeast from pouch with yeast nutrient added to the boil) Thanks
It def sucks when you blow off a large percentage of your beer, like Utahbeerdude said, you're gonna want to get a bigger fermenter. Either that or just don't make 5 gal batches, shoot for 4.5 or 4 gal so there's some head space left. One last thing, your gravity seems a little high at 1.032, how long has it been fermenting when you took that reading? You may want to let it sit a bit longer it may go down a few more points if you were considering bottling soon. I would be shooting for the 1.02xish range on something like that. Good luck!
1.032 is the predicted FG based on brewersfriend calculation, thanks for the heads up. So how much head space is acceptable? Could I put 5 gallons in a 6 gallon carboy? Would a wider blow off tube (and bung hole) have cut down on some of the wort blowoff?
You don't have to spend a lot of money on a larger fermenter. Get you a 7.5-8 gallon plastic bucket and ferment in that. That's what I used to do. I have two 6.5 gallon carboys and have brewed large OG beers such as yours, some even higher, and they have filled up to the very top with krausen. For 95% of large gravity brews i've fermented in a 6.5 gallon carboy, i've been okay without any issues. Some people have taken a 1.25" O.D. diameter vinyl tubing and inserted it directly into the glass carboy to allow more gas to escape, personally, i've never done it. One other thing you could do is to add Fermcap to your fermenter and it'll help a lot with the foam.
A wider blow-off tube would not help. The key is to keep krausen away from the top of the fermenter. A bigger fermenter and/or use of Fermcap-S will help, especially with big beers. For a not-so-big beer, a 6.5 - 7.0 gallon carboy for a 5 gallon batch is often plenty. However, there are some yeasts that just thrown a hugh krausen no matter the gravity, notably some Belgian and German wheat-beer yeasts. I personally ferment is a 7.9 gallon plastic Speidel fermenter, which I obtained from MoreBeer. I really like it, but it's kind of expensive. A large plastic bucket is a good way to go. Cheers!
In this order: Larger fermenter use Fermcap Ferment cooler Underpitch -- not the best idea. Brew a smaller batch -- terrible idea.
+1 for Fermcap. I use a few drops in the fermenter for big beers and the Krausen never even makes it into the blow-off tube.
