Big russian imperial stout - stall?

[BrewDrum]

I have a RIS 30 plato (1.129 OG) that i used a new yeast - Fermentis High Gravity HA-18. This yeast was a beast at first and I only pitched 7 days ago. Currently the beer ia sitting at 1.034 and I'm seeing a trend on it that appears to may have stalled. I'm going to give it another week just to make sure, but I want to be prepared in case it doesn't.

Currently fermenting at 84F (in the mid range for this yeast). I am contemplating adding S-04 to get it down a few more points, or wondering if i should oxygenate it...thinking it may be too late for that.

Any ideas or tips on what to do? I would like it to get down to around 1.020...

[Weehe]

Honestly I would be surprised if you got it below 1.03 with that starting gravity. What was your mash temp?

[BrewDrum]

I mashed at 149F. This high gravity yeast was supposed to get up to 21% abv (not that i'm trying to get that high)...just want it to drop a few more points. its still too sweet. i know its only been 7 days but its not moved in a few days..

[jebzter]

grain bill? and did you do a forced ferment on it? you will never know exactly how low you can get without a forced ferment, and if you have a high percentage of caramel, crystal or dextrine malts, you will have a certain percentage of unfermentable sugars regardless of mash temp. Your current apparent attenuation is 71%, that yeast should go to 98% according to the mfr. I would bet that you've got some unfermentables in there, or too low of pitch rate for the beer. Stuff this high of OG usually takes more oxygen dose during the growth phase.

[BrewDrum]

grain bill? and did you do a forced ferment on it? you will never know exactly how low you can get without a forced ferment, and if you have a high percentage of caramel, crystal or dextrine malts, you will have a certain percentage of unfermentable sugars regardless of mash temp. Your current apparent attenuation is 71%, that yeast should go to 98% according to the mfr. I would bet that you've got some unfermentables in there, or too low of pitch rate for the beer. Stuff this high of OG usually takes more oxygen dose during the growth phase.

Yeah that's where the confusion lies. I don't have the grain bill in front of me. Surprisingly it doesn't have a big specialty malt percentage. (going off of the top of my head) C120, Roasted Barley, Chocolate Malt, Black Malt, and a ton on Pilsner...even used some light Pilsen DME. I'll have to check percentages later. I aerated the wort before-hand, but there was such an active krausen for the first 4 days, I couldn't aerate moreso than that.

Adding a fresh pitch of S-04 be pointless at this time?

[jebzter]

You would kept the oxygen going post knock out for a period of hours, then cut it off. The DME may be contributing as well. Malt extracts generally are not 100% fermentable, so it may be contributing to your high end point. You're already above S-04 alcohol tolerance, so I doubt it will even kick off, you're nearly at 15%.

[BrewDrum]

I'm almost at 12.5%. I'm just thinking of ways to get it to drop a few more gravity points to be within style guideline. Some is going in whisky barrels, and the rest is being vanilla'd (not the best grammar). I was thinking adding some S-04 might drop it a few, but like you said, there may not be anything left for the yeast to chew on..

Hmmm... Some champagne yeast to drop it a few then cold crash when I hit fg? I'm thinking of anything..

[soia1138]

It's done. You're at 71% apparent attenuation and it's probably never going to go further. Of course its too sweet that's what a SG of 1.129 gets you. You need to use enzyme in the mash for a beer this big or just don't do a beer this big. How many IBU is the beer? At that SG it better be damn near 100. RIS is a sweet beer anyway you look at it, but it's done. You can't expect anything more from the fermentation, hell 71% is actually pretty good.

[UnFermentable]

Of course its too sweet that's what a SG of 1.129 gets you. You need to use enzyme in the mash for a beer this big or just don't do a beer this big. How many IBU is the beer? At that SG it better be damn near 100. You can't expect anything more from the fermentation, hell 71% is actually pretty good.

While I wouldn't strictly agree with most of this, I think it applies to most people trying to do this type of beer. You need to understand the composition of sugars and how to derive them, as well as the dynamics of fermentation to achieve something close to this.

The fact you don't mention pitch rates, grain percentages or aeration levels tells me it is probably a rough road. Too late to aerate now. You can rouse the yeast, build a large starter and re-pitch, or Krausen but you are not likely to raise more than a few more percent attenuation. A different yeast can sometimes help, but you will need increased cell counts of highly active yeast to combat the environment they will now be entering regardless. You have to watch for more dead cell mass as autolysis is likely to occur. The alcohol is toxic to the yeast, and the lack of simple sugars leads to inactivity. You will get an initial drop after re-pitch as the living active cells do some work, but it will stall again quickly.

To Jebzter's point, all this will only help if the composition of sugars can be metabolized by your micro organism of choice (S-04 in this case). Yeast carry enzymes that break down the sugars it needs to metabolize alcohol (among other things). Each enzyme only works on a specific compound. Barley carry enzymes that help convert starch to sugar (A & B Amylase) for the yeast to continue. Both need to work in conjunction to achieve your desired starting and final gravity. Forced fermentation testing is your friend, especially on beers approaching technical limits.

You should have likely been brewing with significant amounts of Dextrose, Sucrose, or Fructose to keep your FG anywhere close to 5*P. Or use industrial enzymes like soia1138 says. This type of situation often happens when trying to scale an existing recipe up to a very high alcohol content. Basically too many unfermentables are left behind in the wort, or the yeast slacks off and doesn't finish the job. Forced ferment will hep you determine.

As Jebzter stated, you need to add oxygen for a prolonged period into the beginning of fermentation. You are too hot at 84, even if that is the recommended range, and I can tell you why. Because it took off so quickly and aggressively. You want "grow more yeast" and not "make alcohol faster" when brewing beers of this style. Major activity shouldn't really show until about the 12-18 hour mark after pitching, so you have time to build cell counts and strength. Oxygen is essential to the yeast cell development and it tends to leave wort very quickly, hence the need to add more. After about 48 hours from pitching you should no longer aerate. Any left over o2 will be problematic with stability. Knocking out a bit cooler would slow things down, even if you let it free-rise back up to 84. You also need to add zinc, or preferably a multi-nutrient combo like servomyces.

Why not just pitch higher rates? Because it will induce a faster more vigorous fermentation and the cells will basically crap out early and not finish the job. Don't aerate "more", but rather "less" for a much longer period. You need newer younger generations to carry on the work until the end. Hopefully they aren't mutated millennials....anyhow, just my $0.02!

[BrewDrum]

thats an amazing response and thank you!

[Foamtime]

It's done! 1.034 is a great finishing grav for a beer that started at 1.129 now it won't taste so boozy. If you really think it's too sweet, condition it on some coffee and cocao nibs.

[Maddog]

You are probably fine

Just a thought, since you are going to be putting this beer in barrels anyway. It has been my experience that a big beer that appears done in the FV will often kick off vigourously upon transfer into the barrel. I had a big stout that was done for over a week at 1.030 and subsequently dropped to 1.018 in the barrel without additional yeast and not contaminated. Not exactly sure why. I think you got excellent numbers on this beer already.

[Ted Briggs]

Notes from White labs Super High Gravity Yeast:

https://www.whitelabs.com/yeast-bank/wlp099-super-high-gravity-ale-yeast

"Flavors from this yeast vary greatly with the beer produced. The higher the gravity, the more winey the result. Beers over 16% ABV begin to taste less like beer, and more like fortified wines.

With low gravity beers, this yeast produces a nice, subtle English ale-like ester profile. As the gravity increases, some phenolic character is evident, followed by the winey-ness of beers over 16% ABV. Most fermentations will stop between 12-16% ABV unless these high gravity tips are performed:

Aerate very heavily, 4 times as much as with a normal gravity beer. Less oxygen dissolves into solution at high gravity.

Pitch 3-4 times as much yeast as normal.

Consider aerating intermittently during the first 5 days of fermentation. This will help yeast cells during a very difficult fermentation. Aerate with oxygen for 30 seconds or air for 5-10 minutes.

Higher nutrient levels can allow yeast to tolerate higher alcohol levels. Use 2 times the normal nutrient level. This is especially important when using WLP099 to make wine and mead, which have almost no nutrient level, to begin with. Do not start with the entire wort sugar at once.

Begin fermentation with a wort that would produce a 6-8% beer, and add wort (it can be concentrated) each day during the first 5 days. This can be done together with aeration. This is mandatory if the reported 25% ABV is to be achieved."

Id add that if you are going to use simple sugars add them in the FV not kettle. Let the robust yeast tackle the maltose and maltotriose at the start of fermentation. I have achieved 17%+ in a test batch starting with US-04 and followed by this yeast with additions of Brewers Crystals. https://bsgcraftbrewing.com/brewers-crystals-55-lb

[dick murton]

I used to regularly brew a barley wine at 11%, with a start OG of 1104 and end gravity of 1018 though we later reduced both to 1010 and 1014 respectively and it tasted far better for that. Anyway, the point is that we carried out normal wort aeration with air, so circa 8 ppm O2, and then intermittently aerated after 12 hours, until the PG was somewhere around 1040.

I did an 18% special beer following a similar process, but knocked the intermittent air off a bit too early so ended up at about 1023.

Unfortunately I haven't kept records of the exact regime, and anyway, this was 550 hL batches - so probably somewhat larger than you are brewing.

So my point is, I used the same basic process as indicated by unfermentable and Ted. The big problem with one off batches is knowing when to stop aerating as if you over-aerate, the beer is rather bland, and you under-aerate, it stalls early. We had lots of experience with the barley wine - up to ten brews week, but even this knowledge didn't help with the 18% special. You simply can't extrapolate accurately, which is a great shame, but one of the joys of brewing - it can be rather unpredictable and so tests your mettle as a brewer.