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Old 04-25-2011, 11:44 PM   #1
NJames
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Default IBU confusion

I've got a beer in the fermenter now that I calculated at ~37 IBUs using Palmer's nomographs in How To Brew. When I put it into BeerTools I was shocked to see 60 IBUS!

Why do I get wildly different IBU figures? Which one is correct?

my recipe:
3 gal boil
6 lbs. Briess Gold LME
.5 lbs. Victory
1 oz. Galena 13% for 60 minutes
2 oz. Cascade at knockout

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Old 04-25-2011, 11:47 PM   #2
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At a guess, did you put the 3 gallons into BeerTools?

I'm guessing Palmer's 37 IBUs was for a five gallon batch. I'm guessing you boiled 3 gallons and added another 2 gallons at the end. If that's the case, once you were done boiling, that 3 gallons of wort was 60 IBUs, but after you added about 2 gallons of water it'd be down to about 40 IBUs, which you expected. Does that explain it?

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Old 04-25-2011, 11:48 PM   #3
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According to Beersmith, the 60 IBU number is closer to accurate (for a 3 gallon batch). If you are topping up an extra 2 gallons... the number drops.

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Old 04-25-2011, 11:48 PM   #4
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When did you add the malt extract? All of it at the beginning? with only an ounce of bittering hops, no way you got 60 IBUs! More like 34.

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Old 04-25-2011, 11:49 PM   #5
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Is this a 5 gallon batch? I'm guessing you added water after the boil?

With a 5 gallon batch, I'm getting close to 60.

With a 3 gallon batch, I'm getting close to 100.

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Old 04-25-2011, 11:49 PM   #6
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Quote:
Originally Posted by maffewl View Post
According to Beersmith, the 60 IBU number is closer to accurate.
Haha- we posted at the same time, but gave you exact opposite answers.

With one ounce of 13% AAU hops, I don't see how you could have possibly got 60 IBUs! Not in a 5 gallon batch. A partial boil may decrease hops utilization, but not all that much. I still stand by the 34-37 IBU estimate.
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Old 04-25-2011, 11:50 PM   #7
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Adding an ounce is hops at 60 minutes is almost always going to add a high amount of IBU's because that is where all the bittering comes from. I'm not familiar with the How to Brew nomographs, but FWIW ProMash gave me the same reading that you got. I would say user calculation error, or just outdated information?

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Old 04-25-2011, 11:50 PM   #8
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Quote:
Originally Posted by Yooper View Post
Haha- we posted at the same time, but gave you exact opposite answers.

With one ounce of 13% AAU hops, I don't see how you could have possibly got 60 IBUs!
Lol... I set it up for a 3 gallon batch... misread the OP saying boil.
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Old 04-25-2011, 11:52 PM   #9
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Quote:
Originally Posted by maffewl View Post
Lol... I set it up for a 3 gallon batch... misread the OP saying boil.
Yeah, I saw this as a 5 gallon batch with a 3 gallon boil.
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Old 04-25-2011, 11:54 PM   #10
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Quote:
Originally Posted by Yooper View Post
With one ounce of 13% AAU hops, I don't see how you could have possibly got 60 IBUs! Not in a 5 gallon batch. A partial boil may decrease hops utilization, but not all that much. I still stand by the 34-37 IBU estimate.
We're assuming hop pellets, correct?

http://www.rooftopbrew.net/ibu_calculator2.php
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