Author Topic: Final Gravity Low  (Read 1793 times)

Offline stogies4life

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Final Gravity Low
« on: November 18, 2013, 06:02:09 PM »
I just did an AG Imperial Porter that the FG finished at 1.013 and was supposed to finish at 1.022. The OG was also a bit low 1.066 and supposed to be 1.070. Yes, my hydro is calibrated and my reading were corrected for temp. Have I missed something or done something wrong?


tia,

s4l

Offline morticaixavier

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Re: Final Gravity Low
« Reply #1 on: November 18, 2013, 06:06:40 PM »
I just did an AG Imperial Porter that the FG finished at 1.013 and was supposed to finish at 1.022. The OG was also a bit low 1.066 and supposed to be 1.070. Yes, my hydro is calibrated and my reading were corrected for temp. Have I missed something or done something wrong?


tia,

s4l

details?

Grist, mash temps, and yeast choices all play a major roll in the FG of a beer. I wouldn't worry too much anyway. 1.013 sounds good for an imperial porter to me.
"Creativity is the residue of wasted time"
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Offline stogies4life

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Re: Final Gravity Low
« Reply #2 on: November 18, 2013, 06:35:00 PM »


details?

Grist, mash temps, and yeast choices all play a major roll in the FG of a beer. I wouldn't worry too much anyway. 1.013 sounds good for an imperial porter to me.
[/quote]


Here's the grain bill

13 lbs, 2-Row
.75 lb. Carastan
.5 lb. De-Bittered Black Malt
.25 lb Chocolate Malt

Mashed @ 150 for 60 mins. I do BIAB so no sparge. Boil for 60 mins.
White Labs English Ale 002 that I dbl pitched with one vial and a 2L starter.

I just thought it was odd that it was that low for a FG compared to where it was "supposed" to finish

Offline morticaixavier

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Re: Final Gravity Low
« Reply #3 on: November 18, 2013, 06:46:28 PM »
That is a pretty good fg for that recipe.

when you say 'supposed' do you mean what beersmith is telling you? or was this a kit? I find that beersmith does an okay job or predicting final gravities but yeast attenuation numbers are often off. if you decide you want more body you could up your mash temp a lot, like maybe 155-158ish. Also, I like to include a nice dose of munich (maybe 10%-20%) in my porter because I like the toasty malty richness it lends without the sweetness you can get from too much crystal. Porter, in my mind should be a pretty drinkable dark beer, even imperial versions. So by using some higher kilned base malts and playing with your mash temps you can get a balance between malty and easy drinking.
"Creativity is the residue of wasted time"
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Offline stogies4life

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Re: Final Gravity Low
« Reply #4 on: November 18, 2013, 06:53:04 PM »
This was a kit from Austin Homebrew. And I am still pretty much a noob at this. I have about 10 brews under my belt now

Offline morticaixavier

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Re: Final Gravity Low
« Reply #5 on: November 18, 2013, 07:10:56 PM »
This was a kit from Austin Homebrew. And I am still pretty much a noob at this. I have about 10 brews under my belt now

okay,

kits instructions are getting better but, especially with all grain you can never take the expected targets 100% seriously.
If the instructions had you mashing at 150 and you hit that number, I would also take a moment to calibrate your thermometer. If possible find a NIST certified glass thermo to calibrate against at mash temps. so heat some water till the certified thermo read 150 or so and then check your working thermo against it.

If you do not have access to a certified or other known good thermo you can test it in boiling water (should be ~212, adjusted for your altitude) and ice water (should be ~32) this won't guarantee that it's right at 150 but it might show you if your thermo is way off. and if it's the same amount off at 32 and 212 you can at least try that adjustment next batch and see if you get more accurate results.
"Creativity is the residue of wasted time"
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"errors are [...] the portals of discovery"
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Offline tschmidlin

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Re: Final Gravity Low
« Reply #6 on: November 18, 2013, 07:26:38 PM »
80% attenuation is not unreasonable for a beer that was mashed at 150F, especially if the temp may have dropped or been off by a couple of degrees.  Their predicted FG of 1.022 is a little high for an OG of 1.070 (under 70% attenuation) with that kind of mashing schedule and malt bill.  Plus once you missed the gravity by 4 points you had to expect the FG to be lower as well.

My suggestions are to mash higher to get a higher FG (as mort said), and add some more malt to your recipes from Austin Homebrew to make up for reduced efficiency over what they expect.
Tom Schmidlin

Offline stogies4life

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Re: Final Gravity Low
« Reply #7 on: November 18, 2013, 09:27:59 PM »

[/quote]

okay,

kits instructions are getting better but, especially with all grain you can never take the expected targets 100% seriously.
If the instructions had you mashing at 150 and you hit that number, I would also take a moment to calibrate your thermometer. If possible find a NIST certified glass thermo to calibrate against at mash temps. so heat some water till the certified thermo read 150 or so and then check your working thermo against it.

If you do not have access to a certified or other known good thermo you can test it in boiling water (should be ~212, adjusted for your altitude) and ice water (should be ~32) this won't guarantee that it's right at 150 but it might show you if your thermo is way off. and if it's the same amount off at 32 and 212 you can at least try that adjustment next batch and see if you get more accurate results.
[/quote]


I use a Thermapen to check my temps when I brew and it is spot on. One question for you. When you said earlier that you add 10-20% munich in your porters, is that a percentage of the total grain bill so that I would add somewhere between 1.4 and 2.8 lbs or do you figure it different?

Offline stogies4life

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Re: Final Gravity Low
« Reply #8 on: November 18, 2013, 09:29:44 PM »
80% attenuation is not unreasonable for a beer that was mashed at 150F, especially if the temp may have dropped or been off by a couple of degrees.  Their predicted FG of 1.022 is a little high for an OG of 1.070 (under 70% attenuation) with that kind of mashing schedule and malt bill.  Plus once you missed the gravity by 4 points you had to expect the FG to be lower as well.

My suggestions are to mash higher to get a higher FG (as mort said), and add some more malt to your recipes from Austin Homebrew to make up for reduced efficiency over what they expect.

I figured it would be lower, I just didn't think it would be that much lower. Oh well, I'm learning!

Offline morticaixavier

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Re: Final Gravity Low
« Reply #9 on: November 18, 2013, 09:37:10 PM »


okay,

kits instructions are getting better but, especially with all grain you can never take the expected targets 100% seriously.
If the instructions had you mashing at 150 and you hit that number, I would also take a moment to calibrate your thermometer. If possible find a NIST certified glass thermo to calibrate against at mash temps. so heat some water till the certified thermo read 150 or so and then check your working thermo against it.

If you do not have access to a certified or other known good thermo you can test it in boiling water (should be ~212, adjusted for your altitude) and ice water (should be ~32) this won't guarantee that it's right at 150 but it might show you if your thermo is way off. and if it's the same amount off at 32 and 212 you can at least try that adjustment next batch and see if you get more accurate results.
[/quote]


I use a Thermapen to check my temps when I brew and it is spot on. One question for you. When you said earlier that you add 10-20% munich in your porters, is that a percentage of the total grain bill so that I would add somewhere between 1.4 and 2.8 lbs or do you figure it different?
[/quote]

Yes, a percentage of the grain bill. I would likely add about 3 lbs to that recipe. It would be a good way to bump the total grist up to account for your lower efficiencies as Tom suggested actually.
"Creativity is the residue of wasted time"
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"errors are [...] the portals of discovery"
- J Joyce

Offline ynotbrusum

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Re: Final Gravity Low
« Reply #10 on: November 19, 2013, 11:42:19 AM »
For lighter beers, where I intend to mash at 150F for 90 minutes, I routinely get FG's below 1.010.  Try the same recipe at 154 or above (Mort has said 158 and he has success at that temp - so I did a Scottish 80/- at that temp for 60 minutes and got it to finish at 1.014).  Sometimes, however, the yeast just take it lower than you expect, especially if you are mashing longer.

I followed the advice of some long time homebrewers and repeated the same recipes over and over to get "most" of my system under control, but with healthy repitching, the yeast are one of my biggest variables these days.

Keep on brewing!
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