Post-Boil Gravity and Utilization Weirdness

[Nosybear]

Let's start with this screenshot:

First, it's showing a post-boil gravity of 1.038. This is amazing, since the pre-boil gravity is 1.041. In other words, I'd have to add water to the original wort to get to that number even though I'm boiling for 90 minutes! The original gravity of 1.057 is about right but what I (and a newbie I just answered in another section of the forums) don't understand is why do they differ? I can see the OG being higher or lower if I add sugar or water after flameout but in this recipe, this is not the case (and Brewer's Friend is not equipped to make that kind of calculation).

Second, the hop utilization is at 82%. This is rather unusual: Utillization is generally the amount of iso-alpha acid extracted divided by the dry weight of the hops. It would appear the utilization formula you are using is the amount of iso-alpha acid extracted divided by the iso alpha acid available. Slightly different but odd, particularly if one is looking for utilization figures in the 25%-30% range.

You might want to put help in the form of a question mark or hover-over explanation of what the values are and how you derive them, especially if the calculation appears to make no sense.

 

[Pricelessbrewing]

The pre/post boil issue I just noticed recently as well and documented in the thread below. It's a fairly quick fix and important issue so hope it's corrected relatively soon.

https://www.brewersfriend.com/forum/threads/suggested-fixes-and-features.12138/page-3

 

[Nosybear]

I hadn't noticed it (either the bug or the thread) because it really wasn't of interest to me. Only answering the new guy's question did I even notice it was there! In the absence of a way to handle sugar additions during the boil or during fermentation, it wasn't of any use and, as mentioned, should be a repeat of the OG. My suggestion would be to hide the post-boil gravity until it's fixed. Then it becomes a new feature for anyone who hasn't been a part of the issue and it takes a rock out of the shoes of those of us who have.

 

[Pricelessbrewing]

Hiding postboil won't fix the underlying issue, as preboil gravity is also affected. As a result, the average boil gravity is affected, which means the IBU calculation is also slightly affected due to all of the IBU formulas using boil gravity (either pre, post, or the average of the two).

 

[Yooper]

As far as the hops utilization number, that comes from your settings with the altitude adjustment feature:

For the preboil/post boil things, we are discussing that right now. We're also adding late addition fermentables (primary, secondary, bottling, etc) which affects the OG but not the post boil gravity, etc, so it goes pretty deep into making it all work. Right now we are still looking at the postboil and OG differences and fixing that first.

 

[Nosybear]

Understand. So that utilization figure is the percentage of alpha acid isomerized during the boil? Say I have 10g of a 10% AA hop, I'd wind up with 1g available alpha acid, isomerized to 0.82g iso alpha acid? I'm asking because I generally see utilization as a percentage of dry hop weight, hence my confusion....

 

[Pricelessbrewing]

For the preboil/post boil things, we are discussing that right now. We're also adding late addition fermentables (primary, secondary, bottling, etc) which affects the OG but not the post boil gravity, etc, so it goes pretty deep into making it all work. Right now we are still looking at the postboil and OG differences and fixing that first.

Awesome, looking forward to seeing how that's addressed as it's something I made crucial to the beerJSON recipe project and is super crucial to funky/sour/farmhouse brewing.