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Old 10-29-2009, 09:34 PM   #1
golfguy819
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I just finished up my 5th AG batch and was pretty shocked at how much I boiled off during this boil. I typically boil off 1.5 gallons during a 60 min boil, but today, I boiled off 2 gallons. I go into the boil w/ 7 gallons, so I can get 5.5 into the primary. But today I actually had to use tap water (I know, big NO NO, but I didn't have any bottled water around) to top off to get me over 5 gallons (I was under by a little bit).

So how much do you normally boil off?
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Old 10-29-2009, 09:37 PM   #2
wildwest450
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20-22%, it will vary by nearly every brewer.

 
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Old 10-29-2009, 09:42 PM   #3
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Well...I burn off a gallon per half hour on my system....in the summer....more in the winter. I suspect that's what happened to you.

 
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Old 10-29-2009, 09:43 PM   #4
Scimmia
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Quote:
Originally Posted by wildwest450 View Post
20-22%, it will vary by nearly every brewer.
how does percentage have anything to do with it?

 
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Old 10-29-2009, 10:02 PM   #5
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Typically one gallon per hour at a moderate boil rate. I can exceed two gallons per hour if I run the burner wide open. I've used tap water to top the fermenter up on a number of occasions without problems. When topping up, it's best to add water to the boil kettle prior to flame out which helps reduce the risk of contamination.

 
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Old 10-29-2009, 10:17 PM   #6
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1.5 gallons within a pint every time. took a while to figure out though. i had to eliminate some variables.
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Old 10-29-2009, 10:18 PM   #7
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Quote:
Originally Posted by Scimmia View Post
how does percentage have anything to do with it?
I boil off 20% of 7.5gal, which is 1.5gal, leaving 6 in the kettle, exactly what I typically get.
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Old 10-29-2009, 10:30 PM   #8
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Quote:
Originally Posted by BarleyWater View Post
I boil off 20% of 7.5gal, which is 1.5gal, leaving 6 in the kettle, exactly what I typically get.
And if you boiled 15 gallons in that kettle, would you expect to boil off 3 gallons? No, it would be the same 1.5 gal.

 
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Old 10-29-2009, 11:26 PM   #9
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Quote:
Originally Posted by Scimmia View Post
And if you boiled 15 gallons in that kettle, would you expect to boil off 3 gallons? No, it would be the same 1.5 gal.
You are right, there is no such thing as a % boil off. Because that percentage is not a constant. The rate is a constant, not a floating %.

I boil off 1.3 gallon/hr no matter the wort volume I start with, this is with about 13,000 BTUs going directly to the wort.

 
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Old 10-30-2009, 03:18 AM   #10
BenS
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The surface area of the wort is what dictates the evaporation rate. A pot with a 12" diameter is going to boil off less that a pot with a 15" diameter at the same temp and altitude.

 
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