Slightly Stuck Fermentation...

[smata67]

Doing NB Imperial Stout. Estimated OG is 1.091 and FG is 1.023 in Beersmith (looking for 9% ABV). Fermented S04 (pitched one packet dry into wort) at 66F for 5 days then went to 72 for the last 9. So two weeks in primary, I'm getting FG of 1.036. I will definitely rouse the yeast and give it another week, is this going to be effective? I also have some S-05 which I can pitch directly or make a starter. I'm concerned about pitching the yeast straight into a 7.2% ABV beer. If I need a starter (would prefer to only rouse yeast, but will pitch if I have to), do I take some of this beer and add it to the starter to acclimate the yeast to its future home?

 

[MalFet]

Fast fermentation test, man. Everything else is just guessing.

 

[Bjornbrewer]

you pitched one packet of S04 into a 1.091 beer? dry? Yeah, bad idea. You should have had two packets rehydrated and even then that's a very floculant, low attenuating yeast. I would maybe think about rehydrating the packet of US05 and add that.

Word of wisdom: Never make a starter with dry yeast, but always rehydrate it.

 

[smata67]

The S04 is the dry alternate on that recipe and yes I should have known better. I think I calculated I needed 180 billion, and the packet is a 100 billion, but I've had such good luck with S04 I thought I'd chance it...Anyways, first high gravity beer, lesson learned.

I rehydrated a packet of S05 and pitched yesterday. I also stirred things up. I'll re-check in a week when I transfer to secondary. Worse comes to worse, I'll get some champagne yeast in my next order or throw in some Scottish Ale yeast in two weeks if I get to boiling my next batch, NB's Wee Heavy. I will be doing a starter on this one.

 

[MalFet]

The S04 is the dry alternate on that recipe and yes I should have known better. I think I calculated I needed 180 billion, and the packet is a 100 billion, but I've had such good luck with S04 I thought I'd chance it...Anyways, first high gravity beer, lesson learned.

I rehydrated a packet of S05 and pitched yesterday. I also stirred things up. I'll re-check in a week when I transfer to secondary. Worse comes to worse, I'll get some champagne yeast in my next order or throw in some Scottish Ale yeast in two weeks if I get to boiling my next batch, NB's Wee Heavy. I will be doing a starter on this one.

180 billion cells for 5 gallons of 1.091 beer? Definitely not. You want about twice that.

 

[Bjornbrewer]

750,000 cells x 21,000mL x 23P = 358 Billion cells.

Well lesson learned...hopefully the US05 helps.

Good luck!

 

[smata67]

Well, its been 4 days since I pitched a rehydrated packet of S05 and no drop in gravity at all, nada. I'm going to move on to a Scotch Strong Ale (Wyeast 1728) this weekend and pitch a liter of it in mid-krausen and see if that does the trick. If not, wait another two weeks and dump it onto the trub from the Scotch ale. If all fail, I've picked up a packet of champagne yeast which will go into a starter beforehand. I am now thoroughly convinced of the benefits of doing a starter with beers over 1.070...

 

[smata67]

Actually, rather than fool around pitching another beer yeast, I'm going to make a 1/2 gallon starter with Lalvin EC-1118 and pitch at peak krausen. From what I've read, the stuck fermentation should be removed off the dormant yeast first so as to not affect the new yeast. If this doesn't do it, I don't know what will. I guess one concern, if it works, is overattenuation (or maybe I'm just deluding myself), in which case I will monitor the FG, cold crash and rack it again f it looks like this is happening. Sound like a plan?

 

[MalFet]

Actually, rather than fool around pitching another beer yeast, I'm going to make a 1/2 gallon starter with Lalvin EC-1118 and pitch at peak krausen. From what I've read, the stuck fermentation should be removed off the dormant yeast first so as to not affect the new yeast. If this doesn't do it, I don't know what will. I guess one concern, if it works, is overattenuation (or maybe I'm just deluding myself), in which case I will monitor the FG, cold crash and rack it again f it looks like this is happening. Sound like a plan?

You're not going to get over-attenuation just by pitching new yeast. Maxiumum degree of fermentation is a function of the wort, not the yeast. All that's why you should really do a fast fermentation test to figure out what you're looking at before pitching more yeast.

 

[smata67]

I have some instant bread yeast I could use for this test, maybe I will give it a try. But, I'm pretty sure that 1.036 is way too high a FG, so what does the test do for me? It has to attenuate further, doesn't it?

Doesn't certain yeast attenuate the same wort more than others? Won't a highly attenuating champagne yeast overshoot the FG that would be expected with S-04? What my intent was to "freeze" the yeast out when it hit the expected FG with S-04 too avoid ending up with the beer over dry.

 

[MalFet]

I have some instant bread yeast I could use for this test, maybe I will give it a try. But, I'm pretty sure that 1.036 is way too high a FG, so what does the test do for me? It has to attenuate further, doesn't it?

Not necessarily. A significant portion of "stuck" fermentations are actually caused by wort fermentability problems, particularly those landing in the 60%-70% range. And, of course, it's also possible that this is a yeast problem, and a fast ferment will tell you how far down you can expect to go. If you have a strong reason not to do the diagnostic work you can certainly just dump in another pile of yeast, but you'd be shooting blind.

Doesn't certain yeast attenuate the same wort more than others? Won't a highly attenuating champagne yeast overshoot the FG that would be expected with S-04? What my intent was to "freeze" the yeast out when it hit the expected FG with S-04 too avoid ending up with the beer over dry.

I just reread your post and realize that I didn't understand before that you were planning to pitch champagne yeast. I certainly wouldn't do that if I were in your shoes, but perhaps others will disagree. If there's still fermentation to be done, a proper pitch of s-04/05 should be able to handle it. The fact that the 05 didn't do anything is what makes me think you might have under-fermentable wort. But, of course, I'm just guessing here too. The diagnostics will tell you what the situation is.

 

[smata67]

What would make my particular batch less fermentable? I'm following the recipe as published for the Northern Brewer Imperial Stout:

http://www.northernbrewer.com/documentation/beerkits/ImperialStout.pdf

I don't have my beersmith output handy, but the FG was way lower than 1.036.

 

[MalFet]

What would make my particular batch less fermentable? I'm following the recipe as published for the Northern Brewer Imperial Stout:

http://www.northernbrewer.com/documentation/beerkits/ImperialStout.pdf

I don't have my beersmith output handy, but the FG was way lower than 1.036.

Ah, I assumed (incorrectly) that this was an all grain beer. Still, beer smith won't really be able to tell you what this recipes FG should be, since none of the calculators take recipe formulation into account when predicting attenuation. You're at about 60% right now, which is low but not impossibly so.

 

[smata67]

Well, three days ago on saturday, I pulled two 1/2 cup samples and pitched Red Star Active Yeast in one and EC-1118 Champagne yeast in the other. Three days later, I'm seeing basically no change from the batch, a FG of around 1.032 for all. I did measure 1.036 11 days ago, so there has been some progress in the batch. The champagne yeast maybe 1 point lower, but still pretty much there. I guess fermentation is complete on this one. I currently have some Wyeast 1728 bubbling away on a wee heavy, is there any point in dropping a pint of this into my batch or have I pretty much determined the FG isn't moving from 1.032? I'm approaching 4 weeks in primary. I'm going to transfer to secondary and store for 2 more months.

 

[Bjornbrewer]

I think it's done. maybe you got a bad batch of extract or you boiled to long and vigerous, but there's sugars there that yeast will not break down. you could try adding enzymes (the beno trick), but that could just ruin the beer altogether.

 

[smata67]

I went ahead and dropped about 3 cups of fermenting beer (the NB Wee Heavy I pitched about 18 hours ago--Scotch Ale 1728) and a cup or so of the krausen into the batch. So far today, it is bubbling through the airlock at about once every 20 seconds. Hopefully it continues to eat sugar after finishing the Wee Heavy in it. I'm going to take another reading when I transfer to secondary this weekend.

Between week 3 and 4 it moved from 1.036 to 1.032 after I pitched a pack of S-05. If I can get another 4 points or so, I'm happy. BS says I should land at 1.023, but I think that's a bit aggressive. Tastes fine, if not a bit syrupy and sweet. I'm at 8% alcohol with a target of 9%.

 

[Bjornbrewer]

Beersmith's FG is just a number based on 75% attenuation. It does not take into account the yeast type, fermentation temp, mash temp, malt type, etc. etc. etc. etc. that really determines final gravity. I never use Beersmith's FG number as a number to shoot for.

 

[smata67]

BS does adjust for attenuation depending on yeast selected. Usually, the high end value. I did do a google search on NB Imperial Stout and a high FG seems to happen. I'll post my FG at 4 weeks in primary and again at 2 months in secondary for the record. The airlock is still bubbling every 30 s after I added some high krausen wee heavy 48 hours ago.