IBU calculations and volume

[SimenK]

Hi!

Does the IBU calculations take into account the evaporation rate of the equipment and the time of the addition?

Let's say I add 10 grams of hops at 60 minutes. After 30 minutes, 1 liter has boiled off according to my settings, and I then add 10 new grams of hops, boiling for 30 new minutes. But then the volume has decreased, and the IBU calculations are off, unless the volume change is accounted for.

Best regards,
Simen Kvaal.

 

[LarryBrewer]

The recipe editor's IBU calculator uses the starting boil gravity the entire way. You are correct in observing the boil gravity does increase during the boil and that could be factored into the logic. However, in practice the impact would be pretty small, we are talking fractions of one IBU. Beers that have a lot of mid boil additions would be the only ones to see a difference.

If you setup a 30 minute hop addition, and then vary the OG, you can simulate the impact this has using our stand alone calculator:
http://www.brewersfriend.com/ibu-calculator/

This is something we could look into changing! If you are that interested, a thread could be started in the feature request forum. Go ahead and let us know, or feel free to start the thread.