Stuck fermentation help needed - Northern Brewer Imperial Stout

So I did Northern Brewer's Partial Mash Kit for Imperial Stout using Wyeast 1728 Scottish Ale. I made and stepped up a starter (twice) and should have had more than enough yeast to get through this bad boy.

Well I started with an OG of 1.086 which was right on target for what the recipe called for. That was on 9.7.12 at 1:30 am. I checked it on 9.11.12 and it was down to 1.032. I checked again just now (9.14.12) and the exact same thing 1.032. I see no visible signs of activity I know this doesn't mean much but the gravity staying the same worries me.

A couple things to note. The temperature of the fermenting beer is 67.5 degrees. It is recommended for this yeast to have a temp of 55-70. The first couple of days it was over 70 (74ish) so I put it in a swamp cooler and got it down to between 64-68. Would this drop in temperature after having a higher temperature mess with the yeast and cause it to slow down or stop? Secondly the attenuation for this yeast is 69-73% and based on my OG I should have a final gravity somewhere between 1.026, and 1.023. As it stands right now I have a ABV of 7.07. It should be higher.

So what should I do? Buy some more yeast, make a starter, and re-pitch? Any help would be greatly appreciated. Thanks

On a positive note - my bavarian hefeweizen, arrogant bastard clone, and dead ringer IPA are doing awesome with no problems whatsoever (as well as my blueberry wine and blueberry skeeter pee wine (I call it skeeter blood)

A list of ingredients would help as then we can see what types and amounts of fermentables are there. If the grains were mashed too high you may have a less fermentable wort. In addition, it is possible the extract is less fermentable as well. It really depends.

Yes, depending on where the yeast was when you dropped the temperature, it may have shocked and dropped sooner than it should have. You can gently agitate the primary and try and rouse the yeast back into suspension and allow the temperature to self rise to ambient temperatures to try and help it along as well. I would do these things first before re-pitching. You can also taste your next sample to get a handle on how sweet it still is, it might possibly just be done.

duboman said:

A list of ingredients would help as then we can see what types and amounts of fermentables are there. If the grains were mashed too high you may have a less fermentable wort. In addition, it is possible the extract is less fermentable as well. It really depends.

Yes, depending on where the yeast was when you dropped the temperature, it may have shocked and dropped sooner than it should have. You can gently agitate the primary and try and rouse the yeast back into suspension and allow the temperature to self rise to ambient temperatures to try and help it along as well. I would do these things first before re-pitching. You can also taste your next sample to get a handle on how sweet it still is, it might possibly just be done.

Click to expand...

Duboman thanks for your help. Here are the ingredients:
Grain
.5 lbs English Roasted Barley
.5 lbs English Black Malt
.5 lbs English Chocolate Malt
Fermentables
12 lbs Dark Malt Syrup

I mashed 165 and less as it lost heat. Directions said to do at 170. I am going to leave it for tonight and maybe give it a gentle stir tomorrow. You are recommending taking it out of the swamp cooler? The temp will be about 69 degrees if I do that which shouldn't be a problem.

Using attenuation percentages I'm figuring the lowest gravity possible is 1.023 which would give me an alcohol percentage of 8.25. Right now I'm sitting at 7.07. I'm only low by 1.18 which isn't really that much. I was just hoping for around 9 or 9.5 for a nice warming alcohol note on a cold winter night but now that I'm running the numbers I guess this isn't possible. Also the taste is really good, not too sweet, just about perfect. I do think that it might be done fermenting. Thanks again for the response.

>.I mashed 165 and less as it lost heat. Directions said to do at 170. I am going to leave it for tonight and maybe give it a gentle stir tomorrow. You are recommending taking it out of the swamp cooler? The temp will be about 69 degrees if I do that which shouldn't be a problem.

You mashed out at 165, or conducted the mash at 165?

If you mashed at 165, thats your problem, thats way too high

ArcLight said:

>.I mashed 165 and less as it lost heat. Directions said to do at 170. I am going to leave it for tonight and maybe give it a gentle stir tomorrow. You are recommending taking it out of the swamp cooler? The temp will be about 69 degrees if I do that which shouldn't be a problem.

You mashed out at 165, or conducted the mash at 165?

If you mashed at 165, thats your problem, thats way too high

Click to expand...

Well that's what it was when I put the grains in then it lost heat after I put them in. But I didn't think it was a problem since the directions said to do it at 170. Also aren't those grains being used for flavor and color and not for fermentables?

Edit: Could you explain the difference between mashing out and conducting the mash?
I'm not sure that these grains need to be mashed - more so steeped. But I'm not sure.. I'm new at this and lovin it!

DaBills said:

Well that's what it was when I put the grains in then it lost heat after I put them in. But I didn't think it was a problem since the directions said to do it at 170. Also aren't those grains being used for flavor and color and not for fermentables?

Edit: Could you explain the difference between mashing out and conducting the mash?
I'm not sure that these grains need to be mashed - more so steeped. But I'm not sure.. I'm new at this and lovin it!

Click to expand...

The malts you listed don't need to be mashed; so you're good with steeping them in the 170F-ish range - IMO that's not the root of your problem. More likely that the dark malt was less fermentable than the recipe anticipated.

Mashing is the conversion of starch to sugar by enzymes at a certain temp, and mashing out is done after the conversion is complete - it's adding a bunch of hot water to the mash to bring it up to about 170F to cease any enzymatic activity.

Frodo said:

The malts you listed don't need to be mashed; so you're good with steeping them in the 170F-ish range - IMO that's not the root of your problem. More likely that the dark malt was less fermentable than the recipe anticipated.

Mashing is the conversion of starch to sugar by enzymes at a certain temp, and mashing out is done after the conversion is complete - it's adding a bunch of hot water to the mash to bring it up to about 170F to cease any enzymatic activity.

Click to expand...

I'm curious, so mashing out stops enzymatic activity that could potentially produce off flavors? How do you know when conversion is complete? Thanks for helping out I'm learning all I can so I can attempt AG.

So if the dark malt was less fermentable is there anything I can do? In hindsight what could I have done. Lowered the amount of dark malt and replaced it with a more fermentable malt? But then that would change flavor. Ugh. And how can you anticipate the fermantableness (yes it's a real word) of a specific malt?

The beer tastes good so I guess I shouldn't be discouraged but like I said I was just aiming for some higher alcohol for those cold winter nights.

Try tossing in a champagne yeast and see if that'll drive the gravity down. It's possible your yeast aren't comfortable in the 8% range.

More likely though, is that the malt extract was higher in non-fermentables than the recipe expected. With only 1.5 lbs of steeped grains, and hitting your target gravity, it's unlikely the grains played a role.

kylevester said:

Try tossing in a champagne yeast and see if that'll drive the gravity down. It's possible your yeast aren't comfortable in the 8% range.

More likely though, is that the malt extract was higher in non-fermentables than the recipe expected. With only 1.5 lbs of steeped grains, and hitting your target gravity, it's unlikely the grains played a role.

Click to expand...

Do you think that would adversely affect the flavors of an already tasty beer? Don't get me wrong I do want more alcohol but not if it will ruin the flavor. Thanks for input.

DaBills said:

Do you think that would adversely affect the flavors of an already tasty beer? Don't get me wrong I do want more alcohol but not if it will ruin the flavor. Thanks for input.

Click to expand...

It shouldn't. The champagne yeast won't have all that much to eat, if anything, and won't impact the flavor noticeably. Had you used only champagne yeast, yeah, it'd be much drier. Also, it will ensure you have live yeast for bottling.

The champagne yeast advice was given to me by a brewer at Sun King in Indy, so I trust his judgment.

Does it taste good? Can somebody write a script which posts this automatically whenever "stuck fermentation" is written in a thread. A high gravity reading doesn't mean it will be cloyingly sweet, only your taste buds will tell you that.

From your description, I'd say its done fermenting. Dropping the temperature may have stopped it a few points early but since its all the fermentables are from extract it probably wasn't going to get down super low. Realistically 1.025 may have been possible and 1.032 isn't that far away.

If I were you, I'd leave it sit for a few weeks more. You can probably let it warm back up to ~70F. Its a high ABV beer at this point so it probably needs the extra time to just sit there anyway. Maybe you'll lose a couple gravity points over that time. If you don't, its probably still gonna be good.

kylevester said:

It shouldn't. The champagne yeast won't have all that much to eat, if anything, and won't impact the flavor noticeably. Had you used only champagne yeast, yeah, it'd be much drier. Also, it will ensure you have live yeast for bottling.

The champagne yeast advice was given to me by a brewer at Sun King in Indy, so I trust his judgment.

Click to expand...

Cool, thanks

DrHop said:

Does it taste good? Can somebody write a script which posts this automatically whenever "stuck fermentation" is written in a thread. A high gravity reading doesn't mean it will be cloyingly sweet, only your taste buds will tell you that.

From your description, I'd say its done fermenting. Dropping the temperature may have stopped it a few points early but since its all the fermentables are from extract it probably wasn't going to get down super low. Realistically 1.025 may have been possible and 1.032 isn't that far away.

If I were you, I'd leave it sit for a few weeks more. You can probably let it warm back up to ~70F. Its a high ABV beer at this point so it probably needs the extra time to just sit there anyway. Maybe you'll lose a couple gravity points over that time. If you don't, its probably still gonna be good.

Click to expand...

It tastes good. It may very well be done, as you say. I will let it sit though .

i can't find a partial mash imperial stout at northern brewer, just an extract with specialty grains kit.
12 lbs of dark extract
1/2lb chocolate
1/2lb black
1/2lb roasted
(i cant think of a worse imperial stout recipe)
I don't care what NB lists as a FG, thats going to finish high, really high.
you said you brewed it on 9/7, check it in november

Sorry if that came off as me being a jerk but if it tastes good then I don't see a problem. I'd rather have my RIS a little sweet anyway compared to something with no body and too dry.

amandabab said:

i can't find a partial mash imperial stout at northern brewer, just an extract with specialty grains kit.
12 lbs of dark extract
1/2lb chocolate
1/2lb black
1/2lb roasted
(i cant think of a worse imperial stout recipe)
I don't care what NB lists as a FG, thats going to finish high, really high.
you said you brewed it on 9/7, check it in november

Click to expand...

"Northern Brewer Dark malt syrup is a blend of pale malt with some caramel 60, Munich, and black malt." The LME is only 30L so all those dark malts are needed but probably a little overboard. I think its a pretty basic RIS recipe. I do agree that the FG is probably higher because of all the extract.

DrHop said:

I do agree that the FG is probably higher because of all the extract.

Click to expand...

because of all the dark extract
the 1.5lbs of grains aren't the problem

amandabab said:

i can't find a partial mash imperial stout at northern brewer, just an extract with specialty grains kit.
12 lbs of dark extract
1/2lb chocolate
1/2lb black
1/2lb roasted
(i cant think of a worse imperial stout recipe)
I don't care what NB lists as a FG, thats going to finish high, really high.
you said you brewed it on 9/7, check it in november

Click to expand...

Ohh ok it is the specialty grains kit, I thought it qualified as partial mash. Now I get it. Could you point me in the direction of a good imperial stout recipe that you would recommend?

DrHop said:

Sorry if that came off as me being a jerk but if it tastes good then I don't see a problem. I'd rather have my RIS a little sweet anyway compared to something with no body and too dry.

Click to expand...

Right on. I'm just gonna leave it for awhile. It tastes good and I don't want to mess with a good thing.

I would rack it to a secondary and try to pick up a little yeast and let that sit 3 weeks at 70 to see if you drop a few points, then decide if you want to let it bulk age longer, re-pitch, or go ahead and bottle. It is a RIS so it is going to have more body than most beers, so you may not be that far off, but you don't want a little extra sugar if you bottle them and let them age for 6 months, a sure way to have bottle bombs.

The temperature of the fermenting beer is 67.5 degrees. It is recommended for this yeast to have a temp of 55-70. The first couple of days it was over 70 (74ish) so I put it in a swamp cooler and got it down to between 64-68. Would this drop in temperature after having a higher temperature mess with the yeast and cause it to slow down or stop?

Click to expand...

Yes, it quite possibly could have, but most likely it is the extract as others have said.

1.032 isn't that bad of a FG for a RIS. I just did an AG one that finished at 1.030 with a OG of 1.100. Surly Brewing Darkness finishes at 1.039 if you calculate from information on their website.

DaBills said:

Ohh ok it is the specialty grains kit, I thought it qualified as partial mash. Now I get it. Could you point me in the direction of a good imperial stout recipe that you would recommend?

Click to expand...

for 5 gallon extract recipe
10lbs light/ex-light DME (if you prefer LME it would be a good time to try 12lbs Norther brewers marris otter since its a converted AG recipe)
1.25 lb Roasted Barley
.75 lb Special B Malt
.75 lb Chocolate Malt
.50 lb Cara-Pils/Dextrine malt (sub 10L crystal if you have too)
4oz challenger 60minutes
2oz kent goldings 30 minutes

s-04 dry
it works best pitching on a cake from a prior batch

1 month primary
6 months secondary
4-6 months bottle conditioning

amandabab said:

for 5 gallon extract recipe
10lbs light/ex-light DME (if you prefer LME it would be a good time to try 12lbs Norther brewers marris otter since its a converted AG recipe)
1.25 lb Roasted Barley
.75 lb Special B Malt
.75 lb Chocolate Malt
.50 lb Cara-Pils/Dextrine malt (sub 10L crystal if you have too)
4oz challenger 60minutes
2oz kent goldings 30 minutes

s-04 dry
it works best pitching on a cake from a prior batch

1 month primary
6 months secondary
4-6 months bottle conditioning

Click to expand...

Nice, thanks.

DaBills said:

Right on. I'm just gonna leave it for awhile. It tastes good and I don't want to mess with a good thing.

Click to expand...

It'll very likely turn out really good. 1.032ish is fine with an RIS in my opinion. Don't let the naysayers let you think otherwise. If the FG has stabilized for a couple/few days at a stable temp, it's done and can be bottled - age won't hurt it though.

Frodo said:

It'll very likely turn out really good. 1.032ish is fine with an RIS in my opinion. Don't let the naysayers let you think otherwise. If the FG has stabilized for a couple/few days at a stable temp, it's done and can be bottled - age won't hurt it though.

Click to expand...

Thanks, I tasted it again today when I was checking gravity (unchanged) and it tastes awesome so I'm not worried. I do want to let it sit in primary for a little longer. Unsure as to whether I should do secondary or not. Directions that came with kit say to put it in secondary for 2-3 months. Can I just leave it in primary instead with no negative effects? I was thinking of bottling after Thanksgiving and drinking around Christmas.

Today I took it out of the swamp cooler so it should be at about 70 degrees now. I also gently stirred as per duboman's advice earlier in the thread. I'm not too concerned about lowering gravity now but if it works, it works.

DaBills said:

Thanks, I tasted it again today when I was checking gravity (unchanged) and it tastes awesome so I'm not worried. I do want to let it sit in primary for a little longer. Unsure as to whether I should do secondary or not. Directions that came with kit say to put it in secondary for 2-3 months. Can I just leave it in primary instead with no negative effects? I was thinking of bottling after Thanksgiving and drinking around Christmas.

Today I took it out of the swamp cooler so it should be at about 70 degrees now. I also gently stirred as per duboman's advice earlier in the thread. I'm not too concerned about lowering gravity now but if it works, it works.

Click to expand...

If you let it go 2-3 months, you should probably secondary it. That's a long time.