Kit IBU range nowhere near BeerSmith calculations

[thisisjohnbrown]

I got Jason Breatt's Honey Stout kit, made and bottled with no problems.

However, I went to store the recipe in BeerSmith, and got completely different IBU details. The kit says it should be 30-34, but BeerSmith says 13.3. What do I believe here?

Also, I classified it as a Sweet Stout. Is that right?

 

[broadbill]

My guess the IBU calc from the kit assumes you are doing a full boil, but you have Beersmith set up to calculate IBUs as partial boil.

 

[Brewskii]

My guess the IBU calc from the kit assumes you are doing a full boil, but you have Beersmith set up to calculate IBUs as partial boil.

+1
Don't know what the difference would be but more boil volume in BS2 will increase your hop utilization and therefore your IBU ( as it should in real life ).
Seems like a difference of 15 is large for that to be the case based on a single bittering addition. You probably already did but double check the addition times and be sure to adjust the hop alpha acids based on what the package said if you can (i know you already brewed but the recipie instructions would assume average numbers, just like BS so this prob won't help)

 

[ReDim]

Is it possible that you have incorrectly entered something into BeerSmith ?

Like the sequence of HOPS or their respective Alphas?

Could you have been using Northern Brewer [10%] @ 60 and then 2 Cascades for Aroma?

 

[broadbill]

+1
Don't know what the difference would be but more boil volume in BS2 will increase your hop utilization and therefore your IBU ( as it should in real life ).
Seems like a difference of 15 is large for that to be the case based on a single bittering addition. You probably already did but double check the addition times and be sure to adjust the hop alpha acids based on what the package said if you can (i know you already brewed but the recipie instructions would assume average numbers, just like BS so this prob won't help)

There could also be differences in IBU calculation between kit and BS...although calculations seem to be closer at lower IBU recipes.

Anyway, there is a 50% decrease in IBUs with a 50% decrease in boil volume (roughly anyway 5 gal to 2.8gal). Didn't think this was a linear relationship, but I don't know.

 

[ReDim]

http://www.brewersfriend.com/ibu-calculator/

If you do: Northern Brewer @ 60 minutes
Cascade @ 5 minutes

You will get the targeted IBU

Also
In the context of Northern Brewer and Cascade it would make scenes for Northern Brewer to be used as a bittering and Cascade for flavor.

Also like I said Do Check the package for Alpha and do not assume that software will automatically calculate Alpha, Sometimes I have seen that there is a difference between what Software believes the Alpha is and what the packaging says.

 

[ArcaneXor]

Probably just a matter of using different formulas. Tools --> Options --> Bitterness, and use one of the other formulas to see if that gets you closer.

IBU numbers are useless unless they are accompanied by a statement on how that number was determined. The difference between the different formulas, and between calculated and actual IBUs, can be 100%, and in some rare cases, orders of magnitude.

 

[beergolf]

It could be different options for the method used. Is it Tinseth, Rager or one of the others?