Weird Calc with Beersmith on IBUs

[brewmeister13]

I'm trying to plan for my first "big" beer. A 1.135 OG Imperial Stout. While planing i noticed something that I thought was weird with Beersmith. I am planning on boiling my hops for 90 minutes. To see where I should be when I add my hops and start the 90 minute timer I set boil time to 90 minutes. The IBU's were calculated at 121. Realistically I think the total boil time will be 3 hours or 180 minutes. I changed the boil time accordingly and the IBU's jumped to 137.2. Why is this? The hops are still boiling for the same 90 minutes and the wort should be at the same gravity.

 

[koozie]

Did you make sure the hops are added at the 90 min mark still?

Sent from my SGH-M919 using Home Brew mobile app

 

[brewmeister13]

Yeah, I didn't change the addition time at all. I just double checked and it was 90 for both.

 

[divrguy]

Are you saying you took the same hops and changed the boil time to 180 and the IBU went up? If so, it should go up. What am I missing?


Cheers!

 

[geoffm33]

Are you saying you took the same hops and changed the boil time to 180 and the IBU went up? If so, it should go up. What am I missing?


Cheers!

I think he is saying he setup a 90 minute boil with the hop addition at 90 minutes getting 121 IBUs. Then he set the boil to 180 minutes, and made sure the hop addition stayed at 90 minutes. So the hops would be boiling the same amount of time. Yet the IBU's went up.

My guess is it has to do with water volumes/boil off? Though that doesn't sound right. As hop utilization would be worse, not better, with lower volumes after 90 minutes of boil prior to the addition.

 

[ArcaneXor]

I verified it on my copy of BeerSmith. It's a bit odd.

 

[divrguy]

I think he is saying he setup a 90 minute boil with the hop addition at 90 minutes getting 121 IBUs. Then he set the boil to 180 minutes, and made sure the hop addition stayed at 90 minutes. So the hops would be boiling the same amount of time. Yet the IBU's went up.



My guess is it has to do with water volumes/boil off? Though that doesn't sound right. As hop utilization would be worse, not better, with lower volumes after 90 minutes of boil prior to the addition.

Ahhh... Thanks for that.

Option 1- So, if I start off with 5 gallons, boil for an hour, then have 4 gallons, add hops, boil for an hour... My IBU is X

Option 2 - Then start with 5 gallons, add hops, boil for an hour my IBU should be lower than X

That's what should happen. I'm thinking that is what is happening which is correct.


Cheers!

 

[losMythos]

The only thing I can think of is that now with it changed to 180min your boil off is greater and you have less volume at 90min with the same hop addition that might get you a higher IBU. You are essentially hoping less wort at the 90 min mark with a 180 min boil then with a 90 min boil. right?

 

[divrguy]

The only thing I can think of is that now with it changed to 180min your boil off is greater and you have less volume at 90min with the same hop addition that might get you a higher IBU. You are essentially hoping less wort at the 90 min mark with a 180 min boil then with a 90 min boil. right?

^^ agreed


Cheers!

 

[geoffm33]

Ahhh... Thanks for that.

Option 1- So, if I start off with 5 gallons, boil for an hour, then have 4 gallons, add hops, boil for an hour... My IBU is X

Option 2 - Then start with 5 gallons, add hops, boil for an hour my IBU should be lower than X

That's what should happen. I'm thinking that is what is happening which is correct.


Cheers!

The only thing I can think of is that now with it changed to 180min your boil off is greater and you have less volume at 90min with the same hop addition that might get you a higher IBU. You are essentially hoping less wort at the 90 min mark with a 180 min boil then with a 90 min boil. right?

Yeah, I think that is right. Not sure why I was thinking the hop utilization would be worse with the lower volume.

 

[divrguy]

Yeah, I think that is right. Not sure why I was thinking the hop utilization would be worse with the lower volume.

It took me a minute too... Not enough coffee yet..lol


Cheers!

 

[LLBeanJ]

Option 1- So, if I start off with 5 gallons, boil for an hour, then have 4 gallons, add hops, boil for an hour... My IBU is X

Option 2 - Then start with 5 gallons, add hops, boil for an hour my IBU should be lower than X

I could be misreading the OP, but I think what he is describing is this:

Option 1- So, if I start off with 6.5 gallons, add hops and boil for 90 minutes. Final volume is 5.0 gallons... My IBU is X.

Option 2- Start with 8.0 gallons, boil for 90 minutes (volume reduced to 6.5 gallons), add hops and boil for another 90 minutes. Final volume is 5.0 gallons... My IBU is NOT X. Why not?

 

[divrguy]

I could be misreading the OP, but I think what he is describing is this:



Option 1- So, if I start off with 6.5 gallons, add hops and boil for 90 minutes. Final volume is 5.0 gallons... My IBU is X.



Option 2- Start with 8.0 gallons, boil for 90 minutes (volume reduced to 6.5 gallons), add hops and boil for another 90 minutes. Final volume is 5.0 gallons... My IBU is NOT X. Why not?

LLBeanJ, you may be on to something. If that's what the OP is saying... That would be weird because that is essentially the same boil. Might be a good question for Brad Smith if that's whats going on.


Cheers!

 

[geoffm33]

I can't replicate the issue. The theory above makes sense, but in beersmith I can't replicate.

Create new recipe, 60 minute boil, 1oz Amarillo at 60 minutes. Total Mash Water Needed 7.59gal (BIAB). IBU is 44.8

Change boil time to 180 minutes, addition still at 60, Total Mash Water Needed is 9.59gal. IBU still at 44.8.

Beersmith adds water to compensate for the boil off and keeps the IBU's and batch size intact.

 

[divrguy]

I can't replicate the issue. The theory above makes sense, but in beersmith I can't replicate.

Create new recipe, 60 minute boil, 1oz Amarillo at 60 minutes. Total Mash Water Needed 7.59gal (BIAB). IBU is 44.8

Change boil time to 180 minutes, addition still at 60, Total Mash Water Needed is 9.59gal. IBU still at 44.8.

Beersmith adds water to compensate for the boil off and keeps the IBU's and batch size intact.

Who knew we could accomplish so much in so little time...lol. Great test... I would think and hope that's what Beersmith should be doing so that's a good thing. love Beersmith! Thanks for the test Geoffm33


Cheers!

 

[geoffm33]

Who knew we could accomplish so much in so little time...lol. Great test... I would think and hope that's what Beersmith should be doing so that's a good thing. love Beersmith! Thanks for the test Geoffm33


Cheers!

I'm on the east coast, more time to get coffee coursing through the veins.

 

[LLBeanJ]

I can't replicate the issue. The theory above makes sense, but in beersmith I can't replicate.

Create new recipe, 60 minute boil, 1oz Amarillo at 60 minutes. Total Mash Water Needed 7.59gal (BIAB). IBU is 44.8

Change boil time to 180 minutes, addition still at 60, Total Mash Water Needed is 9.59gal. IBU still at 44.8.

Beersmith adds water to compensate for the boil off and keeps the IBU's and batch size intact.

Perhaps there is a checkbox in BS that is/is not checked. I can replicate what the OP is describing. I took one of my recipes with 26.4 IBUs after a 60 min boil and did nothing else except change the boil time to 120 min. IBUs went to 28.0. I made no changes to the hops quantity or times of the additions.

 

[divrguy]

Dang it I'm not in front of my computer so I can't check..lol


Cheers!

 

[geoffm33]

Perhaps there is a checkbox in BS that is/is not checked. I can replicate what the OP is describing. I took one of my recipes with 26.4 IBUs after a 60 min boil and did nothing else except change the boil time to 120 min. IBUs went to 28.0. I made no changes to the hops quantity or times of the additions.

Must be. I opened one of the BS sample recipes and did the same and the IBU's changed.

 

[geoffm33]

You know what it is. I created a new recipe and ONLY added the hops. The IBU's remained the same regardless of boil time with the addition time static. BUT when I added grain, the behavior mimicked the OP (and the rest of the tests).

 

[divrguy]

So more is going on with the wort than I know of then. I wouldn't have that it would change but I'm not a brewmaster. At that high of an IBU it may not be noticeable but if it does the same at a very low IBU (like 20-40) it may be very noticeable.

So whats really happening with the wort? Now is a good time for Yooper to chime in.. Lol


Cheers!

 

[divrguy]

I'm trying to plan for my first "big" beer. A 1.135 OG Imperial Stout. While planing i noticed something that I thought was weird with Beersmith. I am planning on boiling my hops for 90 minutes. To see where I should be when I add my hops and start the 90 minute timer I set boil time to 90 minutes. The IBU's were calculated at 121. Realistically I think the total boil time will be 3 hours or 180 minutes. I changed the boil time accordingly and the IBU's jumped to 137.2. Why is this? The hops are still boiling for the same 90 minutes and the wort should be at the same gravity.

Maybe the key is in the last sentence. Will the wort ACTUALLY be at the same gravity at that point in time? Maybe not and maybe that's why the utilization changes?


Cheers!

 

[geoffm33]

Maybe the key is in the last sentence. Will the wort ACTUALLY be at the same gravity at that point in time? Maybe not and maybe that's why the utilization changes?


Cheers!

Could be....brewmeister, would you mind posting your recipe as a .bsmx file so we can load into BeerSmith?

 

[judsonp]

Re: volumes: Beersmith appears to do boil-off as gallons per hour (rather than percentage). If you have it compute boil volume from your desired (fixed) end volume (the default way), then at 90 minutes, you will have the same volume, regardless of whether the wort had already been boiling for 90 minutes. You can confirm this by just changing the boil time and looking at the volumes. If you set up equipment with a 5 gal batch volume and 1 gph boil-off, a 60-minute boil starts with 6.2 gal and a 120-minute boil starts with 7.2 gal. (The 0.2 gal is cooling shrinkage.)

Re: change in IBUs:

It looks like what Beersmith is doing is only using the initial (pre-boil) wort gravity to compute IBUs.

I made a test recipe with 5 gal batch volume and 1 gph boiloff (no losses anywhere else), 70% efficiency, 10# of 2-row pale malt, and 1 oz of 14% CTZ hops added at 60 minutes. With a 60-min boil, that's a preboil volume of 6.2 gal, a preboil gravity of 1.041, and an IBU of 57.5. If I increase the boil time to 120 min (preboil volume 7.2 gal), I get a preboil gravity of 1.035 and an IBU of 60.5. If I then increase the amount of 2-row to get a preboil gravity of 1.041 (so, multiply by 7.2/6.2, which is 11.6 lb), I get back an IBU of 57.5.

So I think that's your answer. Wort gravity factors into the IBU computation, and Beersmith simply uses the batch's pre-boil gravity for computing this, even if the gravity at the time of the addition is different.

 

[divrguy]

Re: volumes: Beersmith appears to do boil-off as gallons per hour (rather than percentage). If you have it compute boil volume from your desired (fixed) end volume (the default way), then at 90 minutes, you will have the same volume, regardless of whether the wort had already been boiling for 90 minutes. You can confirm this by just changing the boil time and looking at the volumes. If you set up equipment with a 5 gal batch volume and 1 gph boil-off, a 60-minute boil starts with 6.2 gal and a 120-minute boil starts with 7.2 gal. (The 0.2 gal is cooling shrinkage.)

Re: change in IBUs:

It looks like what Beersmith is doing is only using the initial (pre-boil) wort gravity to compute IBUs.

I made a test recipe with 5 gal batch volume and 1 gph boiloff (no losses anywhere else), 70% efficiency, 10# of 2-row pale malt, and 1 oz of 14% CTZ hops added at 60 minutes. With a 60-min boil, that's a preboil volume of 6.2 gal, a preboil gravity of 1.041, and an IBU of 57.5. If I increase the boil time to 120 min (preboil volume 7.2 gal), I get a preboil gravity of 1.035 and an IBU of 60.5. If I then increase the amount of 2-row to get a preboil gravity of 1.041 (so, multiply by 7.2/6.2, which is 11.6 lb), I get back an IBU of 57.5.

So I think that's your answer. Wort gravity factors into the IBU computation, and Beersmith simply uses the batch's pre-boil gravity for computing this, even if the gravity at the time of the addition is different.

Makes sense to me. Learned something new again! Thanks


Cheers!

 

[brewmeister13]

Re: volumes: Beersmith appears to do boil-off as gallons per hour (rather than percentage). If you have it compute boil volume from your desired (fixed) end volume (the default way), then at 90 minutes, you will have the same volume, regardless of whether the wort had already been boiling for 90 minutes. You can confirm this by just changing the boil time and looking at the volumes. If you set up equipment with a 5 gal batch volume and 1 gph boil-off, a 60-minute boil starts with 6.2 gal and a 120-minute boil starts with 7.2 gal. (The 0.2 gal is cooling shrinkage.)

Re: change in IBUs:

It looks like what Beersmith is doing is only using the initial (pre-boil) wort gravity to compute IBUs.

I made a test recipe with 5 gal batch volume and 1 gph boiloff (no losses anywhere else), 70% efficiency, 10# of 2-row pale malt, and 1 oz of 14% CTZ hops added at 60 minutes. With a 60-min boil, that's a preboil volume of 6.2 gal, a preboil gravity of 1.041, and an IBU of 57.5. If I increase the boil time to 120 min (preboil volume 7.2 gal), I get a preboil gravity of 1.035 and an IBU of 60.5. If I then increase the amount of 2-row to get a preboil gravity of 1.041 (so, multiply by 7.2/6.2, which is 11.6 lb), I get back an IBU of 57.5.

So I think that's your answer. Wort gravity factors into the IBU computation, and Beersmith simply uses the batch's pre-boil gravity for computing this, even if the gravity at the time of the addition is different.

Awesome!:rockin: Thanks for all of the help and to everyone else who helped. That's why I love this site. Looks like I'm using the 90 minute statistics. This is a very helpful/interesting glitch to know about BrewSmith.

Could be....brewmeister, would you mind posting your recipe as a .bsmx file so we can load into BeerSmith?

I'm not even sure how to do that. Though the problem seems solved is it possible to save as a .bsmx file on a mac?

 

[geoffm33]

I'm not even sure how to do that. Though the problem seems solved is it possible to save as a .bsmx file on a mac?

You can export from the Mac version by Control-Clicking the recipe from the recipes list and choosing "Export Selected".