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Old 10-13-2012, 05:32 AM   #1
mclamb6
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Default Attentuation question...

I've got an oatmeal stout in primary (5 gallon batch) with the following grain bill:

6.5 lbs Marris Otter
1.75 lbs 2 row
.5 lbs medium crystal (C60)
.75 lbs roasted barley
.75 lbs chocolate malt
.25 lbs dark crystal
1.75 lbs flaked oats
.5 lbs DME (left over extract from the starter)

Using WLP002 with a starter (probably slightly underpitched)
Oxygenation = vigorous shaking of fermenter before pitching

Mashed at 151-152 for 60 minutes

OG was 1.070.

According to BeerTools, FG is supposed to be around 1.017. After almost two weeks, gravity is 1.024 (fermenting at 68-70 degrees).

With the amount of unfermentables that I have, can I expect the beer to drop the additional 7 points or will I end up finishing a bit higher? It's dropped about 6 points since Wednesday. Am I just being impatient?



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Old 10-13-2012, 01:11 PM   #2
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Rouse the yeast and see if it will go lower over then next few days

Are you sure your thermometer is calibrated? Many aren't and you may have mashed warmer than you think.



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Old 10-13-2012, 02:32 PM   #3
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It's a digital, instant read thermometer. I certainly haven't noticed that it is off with any other batch. My OG was actually higher than anticipated, so I don't see how I missed my mash temp. Not to mention that I would have had to really misread the strike water temp to overshoot the mash temp very much.

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Old 10-13-2012, 02:55 PM   #4
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WLP002 tends to drop like a rock. Gently rouse it and bump the temp up a degree or two. If you're still at 1.024 a week later, it's likely finished. Instant read digitals can indeed be off. Since 152F is mid range, if you were off by 2 or 3 degrees and actually mashed at 154F-155F you might note the difference in the amount of unfermentables.

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Old 10-13-2012, 06:14 PM   #5
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Quote:
Originally Posted by mclamb6
It's a digital, instant read thermometer. I certainly haven't noticed that it is off with any other batch. My OG was actually higher than anticipated, so I don't see how I missed my mash temp. Not to mention that I would have had to really misread the strike water temp to overshoot the mash temp very much.
Mash temps will not effect the OG but the FG. High mash temps promote a less fermentable wort and fuller bodies beer or higher FG. Lower temps will promote a more fermentable wort and lower FG and less body.

As Stauffbeir mentioned a +\- 2 degree difference can be the difference of a few gravity points
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Old 10-13-2012, 06:21 PM   #6
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You're at ~66% attenuation, which is within the range posted by White Labs for that strain (63-70%). As already mentioned, if it doesn't change in a week, or so, then chances are the yeast has done all it can. Since it's dropped some more since the middle of the week, it could still be fermenting. Give it the time it needs to finish.

At that OG, I'd give the brew [at least] 3-4 weeks in primary before thinking about going to bottle/keg with it.



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