Imperial stout recipe revision

[Oleson M.D.]

Yes, whenever we brew a high gravity beer.

 

[DBhomebrew]

Sorry, by 'usual' I mean normal gravity. We're comparing big gravity efficiency to low gravity efficiency.

 

[Erik the Anglophile]

well I did a 1.5 hour test boil of 15L, to simulate an average wort boil, and measured the volumes a bit more precisely. Turns out my boil off was set a little bit too high.
Then I did a little scienceing and got a factor of 0.977 to divide my desired at room temp wort volume with to get the adjusted for post mash temp volume I need to collect, so lets say 16.3 L becomes 16.7L when adjusted for the higher temp.
This should get my volumes in better order

 

[DBhomebrew]

I find boil-off to be the most difficult factor to dial in for constancy.

 

[Oleson M.D.]

Yes, we figure 1 gallon to 1 1/2 gallons per hour of boil.
Depending on how vigorous the boil is.

 

[tracer bullet]

Turns out my boil off was set a little bit too high.

Haha I wondered what you were talking about then remembered it was your thread. Sorry if we helped stray off.

Boil off rate is easier w/ electric but even then varies, and as I reminded myself just yesterday also fairly hard w/ propane. I have over the years developed a pretty good idea of what it should look like but even then it can change on the fly - might be my regulator going out. I tend to also make visual checks of the boil-off and if I see markedly higher or lower than about a 1/4 gallon every 15 minutes I can react to it. Factor in water expanding when hot (4% they say), the kettle markings being off, and.... yeah. This is one of those "close is close enough" things for me.

 

[Erik the Anglophile]

Haha I wondered what you were talking about then remembered it was your thread. Sorry if we helped stray off.

Boil off rate is easier w/ electric but even then varies, and as I reminded myself just yesterday also fairly hard w/ propane. I have over the years developed a pretty good idea of what it should look like but even then it can change on the fly - might be my regulator going out. I tend to also make visual checks of the boil-off and if I see markedly higher or lower than about a 1/4 gallon every 15 minutes I can react to it. Factor in water expanding when hot (4% they say), the kettle markings being off, and.... yeah. This is one of those "close is close enough" things for me.

I boil on an electric portable induction heater in the kitchen, but I have the same approach, close enough is good enough. It's just that it has been a bit too off to be comfortable with but I think I might have adjusted it to an acceptable level of accuracy now.
I'll have to try it out in the best bitter I'm gonna brew next, but it will likely be awhile until next brew as our second kid is coming around june and they say attending childbirth is more important than brewing beer. So far I have not really heard any convincing arguments for that proposition but I guess I will have to fold.