Boil Volume/density VS IBUs

[bknifefight]

This weekend I brewed up the 999 Barley Wine which is supposed to range around 90 IBUs. I punched the recipe into Beer Smith and it came out to be around 35. I decided this has something to do with the fact that I am not doing a full boil. I boiled nearly 3 of the 5 gallons of water with the recipe and a little over 12 lbs of DME. Will the volume and density of this boil really drop the IBUs that much? I will taste the beer once it's done fermenting and see if the bitterness is there or not, but for now I feel like I should ask.

 

[TipsyDragon]

the conventional wisdom at the moment is that boil gravity affects hops utilization and thus bitterness. if your scaling down a boil from 5 gallons to 3 gallons you have to also scale down the amount of DME you add to the boil. check out Late Extract Addition.

 

[bknifefight]

I realize that it will be affected, there is no doubt in my mind about that, but would it be affected to drop the number to 1/3 the original?

 

[TipsyDragon]

you can do the math yourself and see. personally i agree with Beer Smith and just about any other brewing software i can think of.

 

[bknifefight]

So it seems I will probably have a pretty unbalanced barley wine on my hands. Any advice on adding bitterness to this beer? Would this be a ridiculous idea: Figure out the amount of extra bittering hops to bring it up to par with what it should be, boil them for an hour in a quart of water/dme mix and add it in with the still fermenting beer?