Hey guys,
Quick question. I just finished brewing my first high gravity beer. It was an Imperial Stout. Finished with an OG of 1.082 and an PABV of 11%. Everything seems to be going great so far. I started with a blow off tube from Saturday (brew day) until today. It blew unbelievably hard until today when I thought it would be safe to switch to a bung and airlock. Fermentation seems to have slowed considerably. I am only getting a bubble through the airlock every 5 seconds or so. So here is my question: Is it normal for CO2 output to slow so quickly. This time last night it was going crazy and tonight it is sedate in comparison. All my other brews have been far lower in gravity and seemed to have slowed at a much more uniform pace. Any advice/answers would be awesome.
Thanks everyone
with an OG of 1.082 you won’t get 11%, You’ll get closer to 8.5% - 9%.
It’s normal for fermentation to slow down after a few days. Judging fermentation by bubbles is generally inaccurate and not advised. A gravity reading is the only true way to determine what’s happening and at what rate.
I’d guess youre fermenting warm, which is why it was so vigorous and fast. What is your fermentation temperature?
Temperature was 67 or 68 degrees. I was using Wyeast Scottish Ale 1728. It says its optimal temp is up to 75, but I kept it away from that high of a temp. If the beer comes in at 8.5 to 9% that’s great. I’m not really shooting at an exact ABV, I just want a good beer. I know judging gravity is the best way to measure fermentation, but I was just nervous of the drastic fall off. I’m hoping that’s normal.
According to their website the temp range is 55-75, and you’ll want to go on the low end of that range because fermentation creates heat. 75 is usually too warm for any ale, better ales are made in the low to mid 60s
If you were fermenting at an ambient temperature of 68, fermentation could have easily been in the mid 70s. which is why fermentation was short and vigorous.
Moral of the story is: what you’re experiencing is normal, but next time try fermenting colder. on the low end of the recommended temperature range. maybe get a bucket and ferment in a swamp cooler
I made the same mistake with this yeast. I thought Scottish ale yeast would finish malty and a bit sweet, but actually this is a very vigorous fermenter. You need to ferment it cool to control the fermentation. I know you don’t want sweet with this yeast, but you do want malty and clean. You probably have a very fruity stout. It will be a tasty beer. It just may take a while longer to smooth out. I am fermenting my latest Wee Heavy at 55 with this yeast.
I have an imperial stout in secondary now. It started 1080, after 2 weeks 1028, after 4 weeks in the secondary i pitched 1/2cup of cocoa and it read 1022. I’m looking to hit 1018 2 weeks after that. I would take a gravity reading after a 10 days in primary, if it seams too high, I have heard of people “swirling” or gently rocking to kick up any stuck yeast.
I used the 1728 with 3 different brews last fall, and kept it in the low-mid 60s. Experienced the same thing- took off big time, real heavy show for about 3 days , then slowed down considerably. Finished perfect to prediction. IMO, a real great yeast.
Alright, thanks for all the help guys. I’m gonna see what I get, but will certainly go cooler next time. Thanks fro the advice.
I just used 1728 for the first time in a scotch ale and didn’t get any blowoff at all, but it did take my gravity from 1.071 to 1.016 in three days (and my expected FG was only 1.020). It was very active for those three days, a lot of bubbling through the airlock, but the krausen never got more than a few inches high and didn’t come anywhere near blowing out. Like yours, mine was in the low to mid 60s (carboy temp, not air temp) the whole time. Guess you never know what exactly is gonna happen with this stuff. The lastest sample tasted great, can’t wait to get this stuff in bottles. :cheers:
