Low Pre-boil & Original Gravity, but High Final Gravity

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Iowa Brewer

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Hey all,

Just finished fermenting an English bitter that had a low pre-boil gravity (Est: 1.049 vs. Actual: 1.042) and a low OG (Est: 1.06 vs. Actual: 1.053), but finished with a higher final gravity than expected: (Est: 1.012 vs. 1.096).

Anyone have insights into how this happens? It's not the first time I've encountered this.

I followed the recommended mash temp (150F with a 168F mash out), and fermentation (67F with a 3-day 71F diacetyl rest).

Cheers!
 

IslandLizard

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Is this unusual, compared to other brews?

Your mash/lauter efficiency may have been was lower than the recipe's estimate. Is this someone else's recipe? Using different malts or crush? Do you crush your own?

You were 7 points low at preboil and also 7 points low in OG. So your boil off was as predicted in the recipe. All good there. ;)

but finished with a higher final gravity than expected: (Est: 1.012 vs. 1.096).
1.096? (my emphasis^) Did you mean to write the estimated recipe's FG was to be 0.996?
If 0.996, that's not a normal FG for English Bitters, 1.008-1.012 being common. It's even too low for many beers, even borderline low for Saisons and Glucoamylase ("Brut") beers.

What yeast did you use? That determines much of the expected attenuation.
 
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Iowa Brewer

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Good questions and thanks for the help on this!
I did type the FG wrong.

Beer Smith estimated 1.060 OG and 1.020 FG.
1.0096 was measured FG, down a 1.053 OG (ABV is 5.70%).
  1. I milled the malts quite fine due to a previous efficiency issue
  2. Recipe is Lou's Best ESB, which I augmented a little bit
  3. Yeast was #OYL-016, for which I made a 1-liter starter, pitched at high krausen
Came out delicious.
Here's a screenshot of my recipe:
 

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Iowa Brewer

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lower actual OG leads to lower FG, assuming same attenuation. so don't expect 1.020 but someting lower like 1.015.
also, at 1.0096 is a lower FG than expected.
Yeah, I completely ballsed-up my initial post.

The central question is, how do I end up with lower OG, and still end up with a higher than expected ABV? It seems counter-intuitive to me that despite having fewer sugars with which to work, I end up with ABV above what I expected.

Sorry for all the confusion 😬
 

marc1

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smccollu

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Yeah, I completely ballsed-up my initial post.

The central question is, how do I end up with lower OG, and still end up with a higher than expected ABV? It seems counter-intuitive to me that despite having fewer sugars with which to work, I end up with ABV above what I expected.

Sorry for all the confusion 😬
your expected ABV would have been (1.060-1.020)*131.25=5.2%. Actual ABV is (1.053-1.0096)*131.25=5.7%.

There is more difference between the actual OG and FG (1.06-1.02=.04) than the estimated numbers (1.053-1.0096=.0434), which means more sugar was eaten and more alcohol produced.
 
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mashpaddled

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It looks like you might have an issue with the way your equipment profile set up. I put the same recipe into beersmith with the stock BIAB profile and got the same estimated OG of 1.060 but an estimated FG of 1.013. It also assumes just 81.7% mash efficiency versus your 91.6%.
 
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Iowa Brewer

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Looks like a sweet set!
It doesn't list the extra decimal on the measurement in the description, is the last digit a guess?
Can you take a picture of the scale on the final gravity hydrometer? I'm curious about how it reads.
Sorry about the delayed reply. Here's a pic of the final gravity hydrometer
IMG_0726.jpeg
 
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Iowa Brewer

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It looks like you might have an issue with the way your equipment profile set up. I put the same recipe into beersmith with the stock BIAB profile and got the same estimated OG of 1.060 but an estimated FG of 1.013. It also assumes just 81.7% mash efficiency versus your 91.6%.
Thanks, mashpaddled! I really should know this, but how did you come to 91.6%?
 
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Iowa Brewer

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your expected ABV would have been (1.060-1.020)*131.25=5.2%. Actual ABV is (1.053-1.0096)*131.25=5.7%.

There is more difference between the actual OG and FG (1.06-1.02=.04) than the estimated numbers (1.053-1.0096=.0434), which means more sugar was eaten and more alcohol produced.
That makes sense. Thanks!
 

bracconiere

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1663273578692.png


not sure if means anything...but i count 20 graduations between 1.000 & 1.010?

and off topic, i bet that thing is fragile! :mug:

edit: i get it now, i'm slow, and never seen a hydro that accurate!
 
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bracconiere

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@Iowa Brewer i bet that thing could be jerry rigged as a kind good mg scale for some stuff!

edit: or cross purpossed for brewing salts or something? just refernce the SG and add to a set amount of water in the cyclinder to get the right gravity....should be acurate to like .5 mg?
 

bracconiere

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Very cool!


maybe, just tried it with 1g magnesium sulfate with a density of 2.66g/cc....should have bumped my 'normal hydro' to 1.008, figuring the 301cc of water (301g's)...only got 1.002... @McMullan would have to smash my dreams of mg scales again on this :(

just thought it should be put on record for my off-topic twist....
 
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Iowa Brewer

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maybe, just tried it with 1g magnesium sulfate with a density of 2.66g/cc....should have bumped my 'normal hydro' to 1.008, figuring the 301cc of water (301g's)...only got 1.002... @McMullan would have to smash my dreams of mg scales again on this :(

just thought it should be put on record for my off-topic twist....
Nobel effort!
 

bracconiere

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Nobel effort!


🤣 i love playing smart stuff like that! it was a hell of a lot of fun! i'm not sure if i just did something wrong or not, should have worked, i think? :mug:

i'll do my best to leave your thread alone now! (just don't forget that reading SG to 0.0005, could be really cool for some reason you don't know yet beside FG!)
 
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