Russian Imperial Stout stopped fermenting 1.050

[MrOdges]

Hi all

I have been trawling around these forums for years, but never registered (yes one of those) but I am in need of some opinions.

So I brewed a RIS a couple of weeks back, which was an interesting experience with that much malt. Based on the Brewdog cocoa psycho, it all went well. Efficiency was around 80%, so hit 1.122. Based on the software estimate, FG was meant to be a quite high 1034. I was using US05 yeast, and it happily bubbled away for about a week (bit less) then settled.

Anyhow, after 'dry hopping' for 3 days with some French oak chips, coffee beans and cocoa nibs - now 2 weeks in - thought it would be good to bottle. However, the gravity is really high. It tastes AMAZING though, not especially sweet at all, and the alcohol is still over 11%.

The catch here is my mash temp was a bit high for what I wanted - didn't know how much temp I would lose with all that grain and its winter (Australia) - as it came in at 72 degrees and held pretty solid. Not ideal I know. But the flavour is what counts, right? 😊

I have tried rousing it, warming it a bit, gently agitating etc but nothing is happening. Has the alcohol got the better of the yeast? But I have read it's done much more than 11% before. Has the higher mash temp just left a whole lot more unfermentable sugars in there? It was meant to be higher FG already of course, so it's not unexpected. I know I haven't posted the recipe (it's on my tablet and I don't have that with me) but any general thoughts? I just don't want to bottle and create 50 or so little bombs. There is enough of that going on already....

Sorry for the long post! Any opinions welcomed.

 

[phendog]

Getting big beers to reach desired attenuation can be frustrating. Your numbers suggest you reached around 57% @9.45%ABV - still a monster beer. Good alcohol, but at that mash temp you definitely ended up with a less fermentable wort leaving a lot of dextrin's behind and will have a stout on the sweeter side. You don't mention fermentation temp, but if you brew this again, try keeping your mash ~65c/150F, aerate well and pitch PLENTY of healthy yeast. Oh, and use a blow off tube.

 

[Rhaop]

I recently brewed an all pale malt barleywine biab, used almost 16lbs of grain and used some light dme to boost the og, anyways i went with a mash rest at 147* then after 45 min lifted the bag heated the wort and did another rest at about 156*, og was 1.110 fg was 1.023 i'm not saying that's the best way but it worked for me having pale malt only helps, darker roast or crystal malts will contribute more unfermentables

 

[MrOdges]

The fermentation temp was 16-17 degrees. Attenuation works out to be 59% based on my numbers. So what's the consensus though? Just proceed and bottle? I may do that if there is still nothing. Been a few days and no visible activity, gravity unchanged. Will just keep an eye on them - if I have to open one and drink it every few days to see if the yeast has woken up...so be it �� If that does happen will just chuck them all in a fridge, but my gut feeling is it's just done.

 

[flars]

Fermentation temperature was fairly cool for US05. It will work at that temperature but with only two weeks in on such a big beer I would be hesitant to bottle so soon. I had a porter that didn't show a drop in SG for a week. Over the next couple of months the SG dropped 7 points in the bottle.

I would warm the beer to about 22°C, rouse the yeast, and give it more time if the flavorings would not become to intense.

SG was taken with a hydrometer?

 

[MrOdges]

Yep SG taken with hydrometer.

I haven't had any issues with those temps before, it is the lower end though.

Will heat it up some more and give it another week.

 

[hottpeper13]

a 72*c (161*f) Mash will denature the beta enzymes,and the alpha will go nuts. So you are most likely done.

 

[MrOdges]

a 72*c (161*f) Mash will denature the beta enzymes,and the alpha will go nuts. So you are most likely done.

Yeah that's what I figure. I don't know why the temps didn't drop as much as normal, and it just held the whole time.

It still tastes amazing though, just the texture is different to 'normal'. But honestly, it doesnt bother me at all!