how much does the boils effect gravity per hour?

[geer537]

Let's say I have a 1.042 wort going into the boil and I know my system boils off about a gallon per hour; How long would I need to boil my wort to get a specific gravity of 1.060?

 

[Double_D]

If you check The Joy of homebrewing on page 374 it has some info. But I'd say you'll have to remove at least two gallons.

 

[JLem]

Depends on your volumes.

Here's a way to help you figure it out assuming you know your volumes:

Preboil gravity points x preboil volume = postboil gravity points x postboil volume

So, if you start with 6.5 gallons preboil:

42 x 6.5 = 60 x postboil volume
Solving for postboil volume gives you 4.55 gallons.

So, you'll have to boil off about 2 gallons, which would take you about 2 hours.

 

[geer537]

Perfect- I knew there was a formula but I could not remember where to find it. I don't think my search terms were good enough either. Thanks all!