Author Topic: Variations in IBU Calculations  (Read 5703 times)

Offline Brewski

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Variations in IBU Calculations
« on: September 14, 2009, 12:18:18 PM »
Hi,
My son & I both use BeerSmith and were working on a recipe.  Using the same hops, %AA, times, & amounts his calculated 62.1 IBU and mine 41.3 IBU. What gives, and more importantly, which one is right.
BTW- Target 11% AA, 1oz. 60min, .5oz. 30min, .5oz 10min.  5.5gal batch size., & all other ingrediants the same.

Offline UselessBrewing

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Re: Variations in IBU Calculations
« Reply #1 on: September 14, 2009, 12:21:30 PM »
Can you post both recipe files for us to look at?

Cheers
Preston
The woodpecker pecks, Not to annoy, But to survive!

Offline Brewski

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Re: Variations in IBU Calculations
« Reply #2 on: September 14, 2009, 12:23:46 PM »
Ok, can you walk me through how to do that?

Offline Brewski

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Re: Variations in IBU Calculations
« Reply #3 on: September 14, 2009, 12:28:56 PM »
Ok, maybe this worked.

Offline Brewski

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Re: Variations in IBU Calculations
« Reply #4 on: September 14, 2009, 12:30:19 PM »
Well, one looks like it did.

Offline UselessBrewing

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Re: Variations in IBU Calculations
« Reply #5 on: September 14, 2009, 02:32:55 PM »
That's great, thanks.

There are a few things going on here, equipment variations/lack there in, Boil volumes, Extract boil times, Mash profiles, Yeast

If you open the pale liquid extract on stout2, you will see one has a boil time of 5 and the other has a boil time of 60 min.
Stout 2 is missing equipment settings and the check is in the "Set Boil Volume Based on equipment"
Stout 2 also has yeast and Stout 1 does not.
Stout 2 is missing the mash profile.

Also for some reason your Target Hops in Stout 2 has a higher IBU than Stout 1. I removed them and added them back but it did not change. I will look into this more and see what I can come up with.

These changes got the two recipies within 3 IBU. I contribute the difference to the Target hops weirdness.

Hope this helps

Cheers
Preston
The woodpecker pecks, Not to annoy, But to survive!

Offline Brewski

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Re: Variations in IBU Calculations
« Reply #6 on: September 14, 2009, 04:17:36 PM »
Hey,
Thanks for the help.
#1 is my set-up, #2 is Kris'.  I guess he's got a little bit of settin up to yet.

Offline UselessBrewing

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Re: Variations in IBU Calculations
« Reply #7 on: September 15, 2009, 06:35:18 AM »
Ok after playing with this for a while, I'm still at a loss as to why there is a discrepancy! I recreated the recipe in my BeerSmith and I get numbers close (.2 IBU) to Kris's (#2). I recreated every detail I could in order to match both recipes.
When you save a recipe it saves everything in a single file. This includes pretty much everything, so I can only assume that any setup/application settings come along with the file. I do know that I am on the latest version of BeerSmith, so I would say you may need to upgrade your version. You can use the automated upgrade from the tools menu.

Hope this helps

Cheers
Preston
The woodpecker pecks, Not to annoy, But to survive!

Offline MaltLicker

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Re: Variations in IBU Calculations
« Reply #8 on: September 15, 2009, 06:44:53 PM »
Under Tools \ Options \ Bitterness, you can select different Hops Utilization Models.  Each model predicts its own level of IBUs, according to the math in the underlying model.  If either brewer changed from the BeerSmith default of Tinseth, that could produce big differences.  If everything else is perfect, I'd check there next. 

Jamil Z uses Rager, so if you're trying to mimic a recipe from Brewing Classic Styles, set your BeerSmith to Rager. 

 

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