Full Boil Question

[clw2112]

Ok, everything i have read always says that you should go with a full 5 gal boil if possible. I am getting ready to brew my first batch and am working on converting an old keg to be my kettle so i CAN go with a 5gal batch.

The kit i have, from Brewer's Best, tells me to only do a 2.5gal boil and has a note about hop utilization and effecting the IBU, which is supposed to be 35-38, since this recipe is calculated for a 2.5 gal boil.

How should i go about this? Is there a formula i can use to change the amount of hops? Any help would be appreciated.

 

[weirdboy]

What kind of beer is it? Can you post the complete recipe? We can help you adjust the hops but need more details.

Basically, your utilization will increase with a larger boil volume, so you will probably want to add less hops to keep things the same.

 

[shecky]

Beersmith can help. If you don't have it, download a free trial version. This could help: http://www.realbeer.com/hops/IBU.html. Or you could tell us the recipe and one of us can help.

 

[clw2112]

Its an Irish Stout, i couldnt figure out how to attached the actual .pdf of the recipe, but here is a link to it:

http://www.brewersbestkits.com/pdf/1023 Irish Stout.pdf

 

[shecky]

Closer but we need the AA% on the hops.

 

[clw2112]

Was afraid of that. Hopefully its on the hops packages in the kit. Ill check on that tonight.

 

[SumnerH]

Beersmith can help. If you don't have it, download a free trial version. This could help: http://www.realbeer.com/hops/IBU.html. Or you could tell us the recipe and one of us can help.

I'd avoid using software corrections for IBUs like this; they're based on the faulty assumption that hop utilization varies with boil gravity. Over the past couple of years, that's been increasingly disproven. There are some effects on final bitterness because isomerized alpha acids tend to adhere to break material, but in extract brews especially those are much, much smaller than what brewing software (or commonly used IBU estimation formulas--Tinseth, Rager, etc) would calculate.

For one data point, Basic Brewing Radio conducted actual measurements of the IBUs in 3 extract beers, one with a boil gravity of 1.127, one with late extract addition for a boil grav of 1.077, and one with a full boil at 1.068. The same hopping schedule was used for all 3.

They then had the IBUs measured in the lab; the final IBUs were very, very close (essentially identical once you corrected for slight variances in the final beer volume do to boiloff, etc).

It's the March 4, 2010 - BYO-BBR Experiment III:
http://www.basicbrewing.com/index.php?page=radio

Search here for "hop utilization" for more info.

 

[clw2112]

Closer but we need the AA% on the hops.

Ok, the Aroma Hops are German Spalt Select AA=2.0% and the Bittering Hops are Palisades Bittering Hopes AA=6.7%. They are pellet hops too, if that makes a difference.

 

[clw2112]

bump

 

[shecky]

Ok, the Aroma Hops are German Spalt Select AA=2.0% and the Bittering Hops are Palisades Bittering Hopes AA=6.7%. They are pellet hops too, if that makes a difference.

Sorry to have forgotten about you for a minute.

I'd avoid using software corrections for IBUs like this; they're based on the faulty assumption that hop utilization varies with boil gravity. Over the past couple of years, that's been increasingly disproven. There are some effects on final bitterness because isomerized alpha acids tend to adhere to break material, but in extract brews especially those are much, much smaller than what brewing software (or commonly used IBU estimation formulas--Tinseth, Rager, etc) would calculate.

For one data point, Basic Brewing Radio conducted actual measurements of the IBUs in 3 extract beers, one with a boil gravity of 1.127, one with late extract addition for a boil grav of 1.077, and one with a full boil at 1.068. The same hopping schedule was used for all 3.

They then had the IBUs measured in the lab; the final IBUs were very, very close (essentially identical once you corrected for slight variances in the final beer volume do to boiloff, etc).

It's the March 4, 2010 - BYO-BBR Experiment III:
http://www.basicbrewing.com/index.php?page=radio

Search here for "hop utilization" for more info.

^This. I did some quick work and it looks like you'd be best going with what the instructions tell you to do. Funny, because the standard rule is (I think) 25% less hops for full boil but that seems not to be the case.

 

[clw2112]

thanks!