Attenuation?'s

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Mainebrew

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I have had my last 2 brews not getting to their projected final gravity #'s. My oatmeal stout finished off high by about 15, it sat in the primary for 3 weeks. These have been all grain beers the oatmeal was pitched a s-33 dry. Now the fat-sam I brewed has been in the primary 9 days and had a s-04 starter and went crazy for 18-24 hrs and had a original of 1.059 and I pulled a sample last night and it was at 1.024 which is about 10 off. I am nervous that something in my routine is not right. Both of those batches went well mashed around 154 both 5 gal batches and both mashed for 60 min. I had good full 60 min boils and had good sanitary practices. Basement temps 66-68 degrees f, and both beers took off good.

Any Ideas on what might cause this? :confused:
 

brewmasterpa

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1.024 is on the high side of the spectrum of final for your particular style. 1.059 is pretty light starting gravity for a stout. well, my stouts usually start at 1.065-1.070. thats cuz, well, i like to get drunk with very little pee. but i think you might be ok. you might try going to a secondary for 10 days and see what you get. if youre at 60F and you drop to 1.020, you might be just fine, but all honesty, i think youre just fine with 1.024. you also said that its only been 9 days. give it 5 more, then go to a secondary for 10 and see what happens.
 

jacksonbrown

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First off, a stout can start pretty much wherever you want it. It all depends on what you're looking for out of the brew.
Am I mistaken, or did you make a starter from dry yeast? If that's the case, that might be your problem. I know you're not supposed to make starters with dry yeast, and I believe it might actually harm the yeast and it's ability to properly attenuate your beer. If that's only the case with one of the brew, well then I don't know. It could be old yeast. Did you check the dates on them? That's all I got. Good luck.
 
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Mainebrew

Mainebrew

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My stout was @ 1.062 and ended around1.028 and the fat sam was @ 1.058 and after 9 days is 1.024. I will let this one go 14 days in the primary and check it again. Projected for the stout was 1.016, and the fat sam is 1.014. I was off my final on the stout by 12.
 
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Mainebrew

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And yes one of the dry yeas the s-04 for the fat sam I made a starter with. But the s-33 for the oatmeal I did not.
 

illinibrew04

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Also, have you checked all your thermometers? A lower fermentation temp could stall the yeast out on you before you wanted...or a high mash temp could contribute to a less fermentable wort. Also, what are your grain bills? The amount of specialty malt might have something to do with it.

cheers,
Nick
 

Yooper

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I wonder about your mash temps- are you 100% sure that your mash temp was 154? If your thermometer was off by 4-6 degrees, then you may have mashed much higher, which would explain the high FGs.
 

Grinder12000

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Not an answer but I'll repeat Yoops answer. HOWEVER - Stouts are really forgiving and even if you do not hit your numbers the brew will tast pretty darn good.

I've missed a few times and I'm the only one to know the flaw - others LOVE the beer.

So yea - numbers are off and it's something to work on but the beer will be great anyway.
 
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Mainebrew

Mainebrew

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My stout tastes pretty darn good even though, and my samples of the fat sam have been good too! I will have to double check the temps with second and third thermometers to verify the control's reading. Thanks guys for the help, I am still in the learning process. So lower mash temps make a more fermentable beer, and higher is drier?
 

Yooper

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My stout tastes pretty darn good even though, and my samples of the fat sam have been good too! I will have to double check the temps with second and third thermometers to verify the control's reading. Thanks guys for the help, I am still in the learning process. So lower mash temps make a more fermentable beer, and higher is drier?
Well, not exactly! Lower mash temps make a more fermentable wort, which makes the beer "drier", finishing with a lower FG. A higher mash temp makes a less fermentable wort, with more long-chain sugars, leaving the beer with a higher FG, and more body and residual sugars.

That's why thermometers are so important- if you mashed at 160 (that's a bit too high anyway but follow my example!) but your thermometer is off by 4 degrees, that would be 164, for example. I don't think you'd get any fermentable sugars out of that. That could explain the high FG, maybe.

For the best "general" mashing in a PM, I'd suggest mashing at 153. You'll be right in the middle of recommended mash temps, but if you actually mashed at 154, that's fine for those recipes.

You can try gently swirling the fermenter to rouse the yeast, and keep it in the middle of the yeast's recommended temperature range and maybe you'll coax a few more gravity points out of it.
 

SpanishCastleAle

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Not much help but the Oatmeal Stout in my sig started at 1.054 and finished at 1.018 which at the time I thought was too high. It was due to a miscal'd thermometer. And going into the keg it was pretty sweet. But after a few weeks in the keg it is damn tasty...just not a beer you pound 4 or 5 of.:) Had I actually hit my FG it might have been a bit too dry for the style.
 

Saccharomyces

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I'm gonna pile on the thermometer theory. Thermo's made for kitchen use are quite often off by 4* or more since most folks don't care about complete accuracy. I calibrate my thermometers before using them and cross check them periodically to make sure one of them hasn't drifted too far off the mark.
 

Bob

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That's a very good question; I'd like to know that, too, before chiming in with anything definitive.

Other than +1 to the thermometer advice. Start with a calibrated instrument, and periodically recalibrate for best results. :mug:

Bob
 

SpanishCastleAle

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Start with a calibrated instrument, and periodically recalibrate for best results.
And def if you happen to drop it. I cal'd my thermometer before my Stout brew session but then noticed it was off after I finished the brew. I'm pretty sure I dropped the thermometer at some point.
 

fixie

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First off, a stout can start pretty much wherever you want it. It all depends on what you're looking for out of the brew.
Am I mistaken, or did you make a starter from dry yeast? If that's the case, that might be your problem. I know you're not supposed to make starters with dry yeast, and I believe it might actually harm the yeast and it's ability to properly attenuate your beer. If that's only the case with one of the brew, well then I don't know. It could be old yeast. Did you check the dates on them? That's all I got. Good luck.
I never knew this. I always make a starter and most of the time it is with dry yeast and I never seem to have a problem. Weird?
 

IowaHarry

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How about moving your fermenter to a warmer location? Maybe it just needs to warm up a bit to finish.
 

Yooper

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I have no idea what is in the oatmeal stout (well, besides oatmeal and "stout stuff") but I'm reasonably sure the "Fat Sam" recipe is mine. SO4 should have brought that down better than it did- that's why I was questioning the themometer.
 

QueenCityALER

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I wonder about your mash temps- are you 100% sure that your mash temp was 154? If your thermometer was off by 4-6 degrees, then you may have mashed much higher, which would explain the high FGs.

+1 Calibrate your therm. If you want a brew with lighter body, do a longer mash at lower temps around 147-149 F. Mash temp. is extremely important to the body- the final gravity- attenuation.
 
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Mainebrew

Mainebrew

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Well back to this post, I did a calibration on the thermo and all was well.
 

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