Strangely low original gravity & IBU calculation

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amh61

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Just finished up my third brew, the furious IPA kit from Midwest. :mug:

Everything went pretty well this morning but I have a few questions.

First, I took a hydrometer reading and got a reading of about 1.032. I used 9.3lbs of LME - something seems really off here. My guess is that the wort and top off water (4 gallon starting boil, down to 3.5 with 1.5 gallons top off) were not fully mixed. But could there be anything else I'm missing.

Second, when I plug the recipe I use into beer calculus I get a very high IBU reading, like past 100. My understanding and cursory research shows that you really can't get higher than 100 IBUs in a homebrew and that amount will be lowered via dilution with top off water. So given that I'm assuming my IBUs for the wort was 100 (3.5 gallons) and I topped off with 1.5 gallons of water I should end up with about 70 IBUs? Am I off base here?

Thanks for any response. I'm not super concerned about any of these problems, as I'm sure it will turn out great (and it is the first time I'm using temperature control). I'll just RDWAHAB.
 

Kingfish

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You are more than likely correct that your gravity reading not being correct is caused by unmixed in top up water.

As far as IBU...You can most definitely get above 100. Looks like that kit comes with 6 ounces of hops. The IBU calculation should be done on the amount into the fermentor. What was the hoping schedule?
 

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amh61 said:
Just finished up my third brew, the furious IPA kit from Midwest. :mug:

Everything went pretty well this morning but I have a few questions.

First, I took a hydrometer reading and got a reading of about 1.032. I used 9.3lbs of LME - something seems really off here. My guess is that the wort and top off water (4 gallon starting boil, down to 3.5 with 1.5 gallons top off) were not fully mixed. But could there be anything else I'm missing.

Second, when I plug the recipe I use into beer calculus I get a very high IBU reading, like past 100. My understanding and cursory research shows that you really can't get higher than 100 IBUs in a homebrew and that amount will be lowered via dilution with top off water. So given that I'm assuming my IBUs for the wort was 100 (3.5 gallons) and I topped off with 1.5 gallons of water I should end up with about 70 IBUs? Am I off base here?

Thanks for any response. I'm not super concerned about any of these problems, as I'm sure it will turn out great (and it is the first time I'm using temperature control). I'll just RDWAHAB.
1) Yes probably not mixed well. Next time you can pull a sample of the wort from the boil and then just do the math with volumes and that gravity to get to your OG.

2) I am showing, using the standard AA rates for Warrior (15%), Citra (13.2%), and Amirillo (8.5%). Boiling about 4.25 gallons down to 3.5 and topping off with 1.5 to get a final volume of 5 gallons you should be at about 58-59 IBUs. Assuming my app is working correctly.
 

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Kingfish said:
You are more than likely correct that your gravity reading not being correct is caused by unmixed in top up water.

As far as IBU...You can most definitely get above 100. Looks like that kit comes with 6 ounces of hops. The IBU calculation should be done on the amount into the fermentor. What was the hoping schedule?
IBU calc should be done on the average amount during the boil. Then whatever the dilution calc is to account for the top off water. Hops utilization really depends on the average gravity of the wort you are boiling, not how much you have in the fermenter.

Edited for more precise facts
 

billl

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Just toss out the OG number. LME is going to hit the target OG of the recipe with only minor variations for the liquid left in the hops and bottom of the kettle.

For IBU, you might plug that into a different calculator. Then remember, these are only calculators and approximations. The vigor of the boil will have a big impact as will the AA of the specific batch of hops you used (vs the standard) and your boil size. Let your tastebuds be the final judge and don't get too hung up on the calculators.
 
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amh61

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Here is the recipe I used adjusted for the AA on the packages of hops. Getting 130 IBUs! Wow.

malt & fermentables



% LB OZ MALT OR FERMENTABLE PPG °L LATE

35% 3 5 Northern Brewer Amber Malt Syrup 36 10 Y

31% 3 0 Briess GOLD LME 34 5 ~

31% 3 0 Briess GOLD LME 34 5 Y

3% 0 4 American Crystal 60L 34 60 ~

Batch size: 5.0 gallons edit
Original Gravity
1.066 / 16.1° Plato
(1.059 to 1.069)
Final Gravity
1.018 / 4.6° Plato
(1.016 to 1.019)
Color
10° SRM / 19° EBC
(Gold to Copper)
Mash Efficiency ?
75% edit
Late Boil Additions
Show | Hide
hops
USE TIME OZ VARIETY FORM AA

boil 60 mins 1.0 Warrior pellet 20.0

boil 20 mins 0.2 Amarillo Gold pellet 10.7

boil 20 mins 0.2 Simcoe pellet 12.9

boil 15 mins 0.2 Amarillo Gold pellet 10.7

boil 15 mins 0.2 Simcoe pellet 12.9

boil 10 mins 0.2 Amarillo Gold pellet 10.7

boil 10 mins 0.2 Simcoe pellet 12.9

boil 5 mins 0.2 Amarillo Gold pellet 10.7

boil 5 mins 0.2 Simcoe pellet 12.9

post-boil 10 mins 0.2 Amarillo Gold leaf 10.7

post-boil 10 mins 0.2 Simcoe pellet 12.9

Boil: 4.0 avg gallons for 60 minutes edit
Bitterness
130.0 IBU / 20 HBU
ƒ: Tinseth edit
NOTE: IBU results higher due to late boil additions
BU:GU
1.97
yeast

Safale S-04 Dry Yeast
ale yeast in dry form with high flocculation and 73% attenuation edit

Alcohol
6.4% ABV / 5% ABW
Calories
218 per 12 oz.
 

Draken

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I am still getting very different numbers. 90.60 for a full boil and 72 for a partial.
 
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amh61

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I wonder why the discrepancy. I guess I'll just have to wait an see how it turns out.
 

Yooper

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IBU calc should be done on the average amount during the boil. Then whatever the dilution calc is to account for the top off water. Hops utilization really depends on the average gravity of the wort you are boiling, not how much you have in the fermenter.

Edited for more precise facts
Actually, wort gravity has NOTHING to do with hops utilization (Palmer himself says he "got it wrong" in How To Brew). He did say that break material "may" impact utilization, though.

Anyway, there is a limit on the amount of hops oils that can isomerize in wort. Generally, that is thought to be around 100 IBUs, no matter how many ounces of hops you add. Above the saturation point, they just can't isomerize further. That's the reason IPAs can be hard to do with a partial boil. If you could get the theoretical maximum of 100 IBUs in the wort (and that's debatable), and have 2.5 gallons of wort with 100 IBUs and add 2.5 gallons of water, you'd have 50 IBUs. That's it. You just can't get higher with a partial boil. The only fix I know of is to buy hops extract (it comes in a bottle) and add that. Well, that and doing a full boil.

Even though calculated IBUs are often shown to be above 100 (Pliny is like 250+ calculated), the reality via testing shows otherwise and that approximately 100 IBUs is the ceiling.
 

Draken

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Yooper said:
Actually, wort gravity has NOTHING to do with hops utilization (Palmer himself says he "got it wrong" in How To Brew). He did say that break material "may" impact utilization, though.

Anyway, there is a limit on the amount of hops oils that can isomerize in wort. Generally, that is thought to be around 100 IBUs, no matter how many ounces of hops you add. Above the saturation point, they just can't isomerize further. That's the reason IPAs can be hard to do with a partial boil. If you could get the theoretical maximum of 100 IBUs in the wort (and that's debatable), and have 2.5 gallons of wort with 100 IBUs and add 2.5 gallons of water, you'd have 50 IBUs. That's it. You just can't get higher with a partial boil. The only fix I know of is to buy hops extract (it comes in a bottle) and add that. Well, that and doing a full boil.

Even though calculated IBUs are often shown to be above 100 (Pliny is like 250+ calculated), the reality via testing shows otherwise and that approximately 100 IBUs is the ceiling.
The tinseth calculation does in fact take wort gravity into account. Now if that calc is wrong is up for debate.

IBU=alpha acid utilization * mg/l of alpha acids
Alpha acid utilization = utilization reduction factor * boil time factor
Utilization reduction factor = 1.65 * .000125^(Avg Wort Gravity-1)
 

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The tinseth calculation does in fact take wort gravity into account. Now if that calc is wrong is up for debate.

IBU=alpha acid utilization * mg/l of alpha acids
Alpha acid utilization = utilization reduction factor * boil time factor
Utilization reduction factor = 1.65 * .000125^(Avg Wort Gravity-1)
Yes, I know. But Glenn Tinseth did that formula a while back, and the thinking has changed. The impact of wort gravity affecting hops utilization has been disproven since then. I don't have the links right now, but there have been interesting conversations with him concerning this that I"ve read/seen. I haven't asked him in person, though, as I do not know him.

Palmer and I have discussed it in person, though.
 

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Yooper said:
Yes, I know. But Glenn Tinseth did that formula a while back, and the thinking has changed. The impact of wort gravity affecting hops utilization has been disproven since then. I don't have the links right now, but there have been interesting conversations with him concerning this that I"ve read/seen. I haven't asked him in person, though, as I do not know him.

Palmer and I have discussed it in person, though.
Very cool info. Thank you. So are one of the other formulas for IBUs better? Do you have links I?

This is why I love this board.. You always learn.
 

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Very cool info. Thank you. So are one of the other formulas for IBUs better? Do you have links I?

This is why I love this board.. You always learn.
No, actually.

I, er, um, use the Tinseth formula myself. :drunk:

The reason is this- even though it's based on a principle proven false (the gravity affecting hops utilization), the formula works mostly. It may not be right for partial boils (that's why Beersmith will give you a huge difference in IBUs for extract brewing with a partial boil) but for the most part it works well. ALL formulas give you a theoretical higher than 100 IBUs for certain beers, but I think it was Vinnie Cilurzo himself that said Pliny was tested as having less than 75 actual IBUs (even though it calculates out to over 200).

That'd be worth a read, if you want to try to find it via Google.
 

Draken

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Yooper said:
No, actually.

I, er, um, use the Tinseth formula myself. :drunk:

The reason is this- even though it's based on a principle proven false (the gravity affecting hops utilization), the formula works mostly. It may not be right for partial boils (that's why Beersmith will give you a huge difference in IBUs for extract brewing with a partial boil) but for the most part it works well. ALL formulas give you a theoretical higher than 100 IBUs for certain beers, but I think it was Vinnie Cilurzo himself that said Pliny was tested as having less than 75 actual IBUs (even though it calculates out to over 200).

That'd be worth a read, if you want to try to find it via Google.
Lol, but after doing some reason I see why it still works. I would think moreso for AG though. The actual utilization has to do with how much break material is in the wort. Since higher gravity brews tend to have more break... The formula holds.
 
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amh61

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Agree. Thanks for the great information Yooper. And thanks again for the second time in one day.
 

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