Possibly Stuck Imperial Stout

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JMSetzler

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I brewed an all-grain imperial stout recently that had an OG of 1.097. I racked it to secondary today (spent 19 days in primary) and when I took my gravity reading, I am getting 1.042, which is an apparent attenuation of about 54%. I used a 1.5L starter of Safale S-05. The starter spent 2.5 days on a stir plate prior to pitching. My wort was sufficiently aerated prior to pitching, and the yeast was pitched at 68 degrees. I was expecting to ferment down to somewhere between 1.025 and 1.030.

I racked this beer to secondary today. I moved it into a room where the temperature is a little warmer. The first 19 days in primary was at a temperature of between 61 and 63 degrees. Today, I moved it upstairs into a room where the temperature hovers around 70 degrees. Hopefully the agitation of racking and the warmer temperature will kick start the yeast and give me a little more fermentation. I will check the gravity again in about a week to see if any additional fermentation has happened.

If, after a week, I haven't seen any additional fermentation, should I try to pitch more yeast? In my previous experience, I have never seen any useful benefit of pitching more yeast to a wort that hasn't fermented out completely. I can't really come up with any ideas as to why this beer hasn't fermented out completely. I paid close attention to details with my yeast starter, aeration, and pitching temperature. What have I missed?
 
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JMSetzler

JMSetzler

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Could be... I hope it ferments down a little more. This entire process with this particular beer has been a learning experience. It's my 11th all-grain batch, but the first with such a large grain bill...
 

pkeeler

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Getting oxygen into high gravity worts is tough. It is also possible your yeast was a little old, which would mean more oxygen demand. I believe you that you aerated well, but it is just hard. I would only pitch more yeast if I thought the alcohol content was too high for the original yeast. But the numbers you give should be ok for an ale yeast.

It is possible that the yeast were using trub lipids in place of oxygen in your primary. When you moved it to the secondary, off the trub, this source of energy was lost. If this was the case, moving it was not a mistake, as lots of off flavors can result from trub lipid utilization. There should be some hardy yeast in suspension still that will finish your beer more. Keep us posted.
 

JetSmooth

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At the very least, it's a great name.

"Hey! Pour me pint o' dat ol' Poss'bly Stuck!"
 

whatsleftofyou

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I suppose it could be an aeration issue, but even shaking the carboy will yield up to 8ppm. Also according to The Crabtree Effect, if the wort is >0.4% glucose (more likely with a big beer) then you don't really need oxygen for fermentation. You could be right but I still lean toward the temp. I'm sure it will drop a fair amount yet either way, just have to exercise a bit of patience.
 
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JMSetzler

JMSetzler

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No additional fermentation after raising the temp to 70 degrees. It's still at 1.042. I pitched another pack of S05 yeast two days ago and there are no signs that it is doing anything. I'll check it again in a few more days, but I think it's done. Maybe I'll pitch some stronger yeast to it and see what happens...
 

dcp27

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if you happened to use lots of dark malts and mashed hot it might account for some of the high FG, but I'd guess that second pitch will get you down more cuz thats just way too high. Probably not what you're going for, but some bretts will get you lower too.
 

archiefl98

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+1 to amylase enzyme. My RIS stuck at 1.044 from 1.090 -- added amylase and seven days later I'm down to 1.026. Figure I got a bad batch of Golden Promise as everything I've made with it has under-attenuated.
 
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JMSetzler

JMSetzler

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Ok... I will give the amylase enzyme a try and see what happens from there. I really hope something will get this stout where it needs to be :) I have never used it before and don't know what's involved. Any tips on that would be appreciated... I'll see if the LHBS has some tomorrow.. if not I'll order some. The good thing about this beer is that time in the fermenter isn't going to hurt it... it's already racked to secondary... It may end up in tertiary before long...
 

archiefl98

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After reading around here on HBT, the common advice is to just sprinkle 1 Tsp of enzyme over the top of the beer. That's what I did and it worked great. I got a container of enzyme from my LHBS for $1.95 -- looks like it'll be enough for about 10-15 batches.
 
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JMSetzler

JMSetzler

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My LHBS didn't have amylase enzyme, so I ordered some, along with some miscellaneous items I need for some upcoming brews. With any luck, I'll get the amylase enzyme in my beer on Friday or Saturday and see what happens from there... After reading the responses here and doing a little outside reading, I'm hoping this will help.
 
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JMSetzler

JMSetzler

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I sprinkled a teaspoon of amylase enzyme in the fermenter about 24 hours ago. There haven't been any visible signs of additional fermentation at this point, but I'll let it sit for a week before I pop the top and take another gravity reading. The centerpiece of my 3-piece airlock is still resting on the center post. No apparent positive pressure from within the fermenter.
 

archiefl98

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Along with the amylase, gently swirl some yeast back up into suspension. Warm the carboy up to 68-70F if you can too. The amylase will break down the chains, the yeast need to be warmed up and in suspension in order to eat them and give you alcohol.
 
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JMSetzler

JMSetzler

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Along with the amylase, gently swirl some yeast back up into suspension. Warm the carboy up to 68-70F if you can too. The amylase will break down the chains, the yeast need to be warmed up and in suspension in order to eat them and give you alcohol.
I did that, even though there should be plenty of yeast still in suspension. It was already warmed up to 70 degrees. I'll check the gravity of this beer again in a few days. If it's still at 1.042, I'm probably going to dump it and try it again.
 
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I had a RIS starting at 1.132 stick at 1.038. I tried everything except amylase enzyme and ended up pitching a new starter of 1500ml WLP099. It got warmer in my house also so long story short I went from 1.038 down to 1.018 right at the low end of the standard. Of course that is estimating with my refrac I will do a hydrometer test when I bottle in a hour or so.
 

dcp27

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so no idea if it would work, but instead of dumping it, what about using it as your mash water if you end up re-doing it? then you wouldn't be wasting it, would already account for some of your ingredients, and have the potential of the new enzyme activity allowing it to break down and become more fermentable
 
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JMSetzler

JMSetzler

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I was planning to dump this beer tonight. I went to check on it and the airlock was bubbling away. One bubble about ever 3 seconds or so. I guess I'll let it sit for another week and check the gravity again...
 
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JMSetzler

JMSetzler

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I cracked open the fermenter on this Imperial Stout today and took a gravity reading... It worked its way down to 1.020 after adding the amylase enzyme. Since it started at 1.097, that finishes this one out at just over 10% ABV. I'm happy with that! I bottled it today...
 
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