Beersmith not calclating IBU for longer boil times

[TheEngineer]

Today I noticed that when I do a 90 min add that gives me 53 IBU, the IBU's don't change if I decrease the time. It's 53 IBU at 80, 70, or 60 minutes. I don't see a change until I change the add to 59 minutes.

Is there a setting I'm missing?

 

[brewfun]

Today I noticed that when I do a 90 min add that gives me 53 IBU, the IBU's don't change if I decrease the time. It's 53 IBU at 80, 70, or 60 minutes. I don't see a change until I change the add to 59 minutes.

Some of it may depend on which calculation you choose.

The plain truth is that IBUs are not an ever upward spiral of bitterness. And it certainly isn't linear.

No matter what you do, you can't get 100% utilization of the hop itself. There is an inverse log scale that says the longer you boil, the fewer IBUs you get per minute.

The calculations all account for this. The BeerSmith utilization number is simply what percentage of the calculation's max will you get.

Most hop isomerization happens in the first 40 minutes, then it flattens out.

Here is an article by Tinseth on this subject:
http://www.realbeer.com/hops/research.html

 

[raysmithtx]

Sounds like you may be adding more time on the hops than you have your boil time set for. Standard is 60 minutes, that's why anything longer does not change until you go below 60 minutes. Change the boil time to 90 minutes and then be sure the hop additions are not set higher than that.


Sent from my iPad using Home Brew

 

[brewfun]

Sounds like you may be adding more time on the hops than you have your boil time set for. Standard is 60 minutes, that's why anything longer does not change until you go below 60 minutes.

The IBU calculation continues upward even if the boil time is shorter than the addition time. The curve becomes more shallow than if the boil time is lengthened. BeerSmith will show an error message in the timer for any ingredients that fall outside the boil time.

The effects are more obvious with higher AA% hops.

On the other end of this, IBUs for a static addition will increase if the boil time is lengthened. Both of these variances appear to be baked into the IBU formulas, and are not specific to BeerSmith. I've observed the same effect in other programs.