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Old 08-28-2011, 10:39 PM   #1
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Default 2 stuck fermentations, the only link is oat malt, does this make sense?

Hi all,

I made a huge imp stout and I was getting ready to bottle (after having washed all of them no less) and I took a fg reading and it came out to be 40. The OG was 90.... the recipe is here:

10# 2row
2# chocolate
1# carapils
2# oat malt
2# roasted barley

I hit and maintained 150 for the whole 60 mins as a single infusion. I did not do an iodine test since I have only recently discovered those. I sparged and hit an OG of 90.

I did another stout which was a repeat of a recipe I used before. The only difference was the addition of oat malt and flaked barley. I added amalase enzyme to the beer and it fermented out to 15 which was great. I just added amazlise now and I hope for similar results. I have never had a stuck mash (I have at least 40 batches under my belt by now and been doing all grain for at least 2 years) but I have never used oat malt. Both of the recipes used oat malt quite heavily (2# in this one, 4# in the other). I have not used oat malt in any other recipe, I have hit all of my temps and come out with outstanding beer... really I can't think of any other thing that could cause 2 stuck fermentations. The other recipe is here:

8# pale 2row
4# oat malt
1# black patent
2# flaked barley

which again, had a stuck ferment at 40. Does this sound right? Should I dough in next time at 122 and let it sit for and hour or something? I can't imagine it was anything else, unless too many adjuncts, but 2-row can convert a lot, esp in an hour.

Thanks so much.

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Old 08-29-2011, 12:32 AM   #2
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I always had a lot of trouble making stouts and porters when I first started out. It seemed they would always get stuck around 1.020 or more. Several things have helped me. First is making sure to pitch enough yeast, which means a starter. Second was to oxygenate the hell of them. Shaking wasn't cutting it for me. Third was to make sure my thermometers were accurate. I discovered my 'ole reliable' was actually 5 degrees off. So I thought I was mashing at, say... 153. But was really 158. That alone will cause the FG to be high. Just some thoughts...
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Old 08-29-2011, 12:34 AM   #3
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That is a heck of a lot of oat malt. Why so much?
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