So I just finished up my Russian Imp. Stout. I usually get about 68% efficiency on my 1.060 OG beers (I use Northern Brewer’s mill) and I planned on losing quite a bit of eff. with this bigger beer. However, I lost a LOT more eff. than I planned. I was hoping to be in the 1.110 range at 63% eff. (what I was shooting for). My OG ended up being 1.088 which is about 51% eff.
Do you think that this eff. loss is typical and I just overestimated my expected eff. or do you think there’s something else at work? I know the setting on Northern Brewer’s grain mill is.040 so I know that’s at least part of the problem.
Very typical. In fact, I find gravity points plus efficiency points to form nearly a constant that can be applied to any beer for a particular brewer and his/her crush and system. Find out your constant and you’re good to go. Actually, with higher gravity beers, the “constant” increases, such that 51% is about the lowest efficiency you will see for any beer up to about OG=1.100. Here’s how this works.
Say for an average beer of about 1.060 your average efficiency is 68%. Okay, so then your constant is 60+68 = 128. So then say you want to make a beer at 1.080. Okay, so subtract 128-80 = 48% efficiency to expect for that beer. But in reality, you’ll never get below 51%, so figure maybe you’ll get around 56%, something like that.
The same correlation works on the other end. For a 1.040 beer, I would expect your efficiency to be around 128-40 = 88%, or maybe a bit lower… maybe you’d hit 82%, somewhere around there.
The closer you are to 1.060, the more accurate this “constant” correlation is.
I agree, that seems reasonable. For really big beers, you may want to reduce the size of your runnings and go for three instead of two, that will give you a bump. Or you could just go for three normal sized runnings and boil longer. That will give you a big bump.
I did an imperial stout with 23 lbs of grain and ended up with 5.5 gallons of 1.103 (post-boil). Efficiency was 69-70% and I did three runnings (two sparges).
EDIT: I also had a friend helping me and we both stirred until our arms were numb.
FWIW, I just made a beer Saturday of average SG 1.055 and I saw over 80% with a single crush at NB’s St Paul store. I was talking to them about a prior beer and he made mention that it was just recently set at 0.035 I believe they can go that low as the rollers are well used. I have always hit minimum 75% typically 80% for average strength beers over the last 12 months before it was recently gauged also.