Learned things this weekend about evaporation

kkimmes · Dec 18, 2012

I fell behind in my brewing lately so I decided to piggyback a double brew batch this past weekend.
When I determine my water volumes, I usually end up with 6.25 gallons of wort before I boil. This weekend, I used my largest 13 gallon brew pot on my outdoor burner versus my 7.5 gallon pot on my inside stove burner. The difference in boil off / evaporation was huge!!!!
Usually at post boil I end up with 5-5.5 gallons of beer, give or take. By using my larger brew pot, with a much larger surface area of wort, in my cold WI garage, I ended up with 4-4.25 gallons of beer post boil. I couldn't believe the difference was so big. Another brew day, another lesson learned.

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45_70sharps · Dec 18, 2012

Boil off is a bitch!
Like you said, you learned something so it's still good.

Did you top it off to your volume?

zachattack · Dec 18, 2012

45_70sharps said:
Boil off is a bitch!

I disagree. As long as you plan for it, high boiloff helps concentrate the wort, letting you sparge with more water and potentially extracting a higher gravity from the same amount of grain.

Xpertskir · Dec 18, 2012

kkimmes said:
I fell behind in my brewing lately so I decided to piggyback a double brew batch this past weekend.
When I determine my water volumes, I usually end up with 6.25 gallons of wort before I boil. This weekend, I used my largest 13 gallon brew pot on my outdoor burner versus my 7.5 gallon pot on my inside stove burner. The difference in boil off / evaporation was huge!!!!
Usually at post boil I end up with 5-5.5 gallons of beer, give or take. By using my larger brew pot, with a much larger surface area of wort, in my cold WI garage, I ended up with 4-4.25 gallons of beer post boil. I couldn't believe the difference was so big. Another brew day, another lesson learned.

I

I

Temperature and relative humidity can also have a large impact on boil off.

kkimmes · Dec 18, 2012

I did not top off. I left it go at around 4 gallons. If I bottled I might have been more particular about it, but I keg. I am a big advocate of the saying, "Relax ... Have a home-brew"

I think two things played the biggest role. Surface area of the wort in the kettle, but even a bigger role was the outside temps were around 34F or so. There was so much steam I could hardly see the top of the wort for the entire 60 minute boil.....