ibu went down on a doubled batch

[Ozarks Mountain Brewery]

had a recipe I created as a 5.5 gallon batch, decided to clone it and then scale to 11, everything doubled correctly but the ibu went down on the 11 batch any idea's why ??

 

[LarryBrewer]

I bet the boil gravity went up because the gap between the boil size and the batch size was reduced. Boil gravity factors into hop utilization, hence impacting the IBUs. If the boil off was also twice the amount, the IBUs would probably be pretty close, but the system corrects for the boil off amount that it was previously set to.

In this situation, the scale feature is torn between trying to keep IBUs the same and keep the flavor the same. Since utilization is a curved function, but the ingredients are scaled linearly. The system favors keeping the flavor the same.

You'll need to adjust the bittering hops to hit the same IBU in this case.

 

[Ozarks Mountain Brewery]

I see, Ive changed my system slightly anyway because in this hot thick air where I live seems to evaporate even more than normal so until I hit my mark on that, Ill just have to live with it lol thanks that makes sense. you know evaporation plays a big part in the way mine finishes, gravity and flavor wise, in the winter I hit everything right on with your site, summer's a different story lol

 

[LarryBrewer]

I see, Ive changed my system slightly anyway because in this hot thick air where I live seems to evaporate even more than normal so until I hit my mark on that, Ill just have to live with it lol thanks that makes sense. you know evaporation plays a big part in the way mine finishes, gravity and flavor wise, in the winter I hit everything right on with your site, summer's a different story lol

Makes sense because the volatile hop oils are being driven off faster in the heat.

 

[Ozarks Mountain Brewery]

for flavor I'm leaning more and more on the last 5-0 minutes and dry hopping otherwise it just goes away after 2 or 3 weeks

 

[LarryBrewer]

for flavor I'm leaning more and more on the last 5-0 minutes and dry hopping otherwise it just goes away after 2 or 3 weeks

Hop flavor diminishes over time. This is true of any beer.