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Old 11-12-2012, 04:59 AM   #1
rumham
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Default Stuck fermentation?

Thanks in advance for any advice on this.

So 16 days ago I brewed my first stout (a partial mash, [URL="http://hopville.com/recipe/1654118"]http://hopville.com/recipe/1654118[/URL).
I mashed on the high end, trying to stay around 158-59 ish, and thought that I had done well with that. I calculated about 67% efficiency prior to the boil, and so proceeded as normal. The boil went fine, and OG came out to around 1.060. After chilling I pitched a 1.5 or so liter starter of Rogue Pacman that I had built up from a few bottles of a hazelnut brown clone I had done last fall and a bomber of Dead Guy. Fermentation started within 4 hours, and seemed to go as usual with Pacman (nice and vigorous). I was fermenting at around 68 degrees F. Tonight, I planned on racking to a secondary on top of a couple bourbon soaked vanilla beans and a touch of oak chips. When I checked the gravity, it came in at an astonishing 1.030. I triple checked this just to make sure.

I know that I because I mashed high there would be a fair amount of unfermentable sugar, but I expected the FG to get to at least in the range of 1.015. Any thoughts or advice? I've never had this problem with any of my other beers, but then again, I tend to mash on the lower end with my pales and IPAs. For the time being, I'll let the beer stay in the primary; I'm hoping the move from the floor to the workbench might've roused the yeast a bit and could help, so I'll check again in a few days. The sample tasted pretty good, albeit obviously a bit sweet. I'd love to get this one to ferment out a bit more to continue as planned. I suppose if not, I could try to pitch some brett and bugs and try my hand at a sour stout. Any and all advice is much appreciated.

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Old 11-12-2012, 05:05 AM   #2
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This is definitely not a mash temp problem, which usually only accounts for a couple points. I would venture a guess it is more an issue with the yeast you built from bottle dregs.

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Old 11-12-2012, 05:13 AM   #3
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Thanks for the quick reply. Any advice on what to do from here then? Repitch? Say screw it and just go with it?

Also, what do you suppose would be the issue with the yeast? I built the starter up from under 500ml over the course of a few weeks, and it seemed that I had a nice healthy bunch before I pitched it.

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Old 11-12-2012, 02:40 PM   #4
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Quote:
Originally Posted by rumham
Thanks for the quick reply. Any advice on what to do from here then? Repitch? Say screw it and just go with it?

Also, what do you suppose would be the issue with the yeast? I built the starter up from under 500ml over the course of a few weeks, and it seemed that I had a nice healthy bunch before I pitched it.
I'm not certain what the real issue is, I'm just pretty sure it's not mash temp... unless your thermometer is terribly calibrated and you mashed at 170F or something. I've made the same beer using mash temps at either end of the appropriate spectrum (148-160) and the fluctuation in OG is maybe 1° plato.
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Old 11-12-2012, 02:54 PM   #5
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You could try to warm it up a bit, bring it up to 75 or so for 24hrs and give it a gentle swirl. It may take off! Only draw back is you may pick up some esters.

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Old 11-12-2012, 04:11 PM   #6
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Quote:
Originally Posted by Mainebrew
You could try to warm it up a bit, bring it up to 75 or so for 24hrs and give it a gentle swirl. It may take off! Only draw back is you may pick up some esters.
I don't think eaters are a big concern at this point, could be, but you've attenuated to the point want to be cautious with oxidizing your beer. I agree, warm it up and see if that helps.
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Old 11-13-2012, 07:13 PM   #7
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A gentle swirl will not hurt, Breweries use pumps to bring beer to the Conditioning tanks. Introducing O2 is what will oxidize beer.

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Old 11-14-2012, 12:20 AM   #8
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I used a 158 mash temp on one of my beers recently and it stopped at 1.027 (Although it started at 1.073)

1.060 down to 1.015 is 75% that's pretty middle of the road. Next time if you want to end at 1.015 mash at 151.

Every degree over 152 will drop fermentable sugars 2% so at 158 you are going to be 12% low. For Pacman that puts you at 63% You ended up with 50% attenuation, so there is something else amiss here. How did you aerate and how much yeast did you pitch? If you didn't give the fermenter a shake for 40 seconds and only pitched one tube that could explain the stall.

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Old 11-14-2012, 05:34 AM   #9
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Quote:
Originally Posted by WoodlandBrew View Post
I used a 158 mash temp on one of my beers recently and it stopped at 1.027 (Although it started at 1.073)

1.060 down to 1.015 is 75% that's pretty middle of the road. Next time if you want to end at 1.015 mash at 151.

Every degree over 152 will drop fermentable sugars 2% so at 158 you are going to be 12% low. For Pacman that puts you at 63% You ended up with 50% attenuation, so there is something else amiss here. How did you aerate and how much yeast did you pitch? If you didn't give the fermenter a shake for 40 seconds and only pitched one tube that could explain the stall.
I aerate via the pour from the boil kettle to the fermenter, and, since I also still have to top up about a gallon, I stir vigorously for a solid five minutes. It's always seemed to work fine for me in the past. As for the pitch rate, I don't have a precise calculation, but as I stated, I built up a starter of Pacman over two weeks from several bottles of a previous batch and a bomber of Dead Guy. I started at just under 500 mL, stepping up three times to a 1.5 L starter. Looked like a nice thick white layer before I decanted and pitched.

It's been 48 hours since I moved the fermenter from the floor up to the workbench (thereby gently agitating it) and warmed it up to the neighborhood of 71 degrees F. I just check the gravity again, and it doesn't look like it's budged. Am I left with no other options than repitching?
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Old 11-14-2012, 12:00 PM   #10
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I would repitch at this point. Did you use DME for the starter or corn sugar? It seems like somehow you have selected cells that can't convert larger sugars. Or perhaps the beer that you harvested from was conditioned with a different yeast than was used for the primary fermentation?

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