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petec
06/18/08 12:32 PM  
terminal gravity on imperial stouts
I've never had great luck with driving down the terminal gravity on my imperial stouts. My OG tend to be around 1.100 and they tend to finish in the 1.028 to 1.036 range. I pitch a pint of recent slurry in them and use pure O2 at pitching. Yeast is usually 1056 but occasionally 1968. mash temp is 144-148F.

I've read some tech literature showing higher FG in darker beers including ones made with large components of roasted and munich type grains.

Anyone have luck driving their RIS down to the 1.020 to 1.024 level without using sugar as part of the fermentables?

petec

tankdeer
06/18/08 12:48 PM  
Re: terminal gravity on imperial stouts
I've on done a couple of them, but yeah, mine finish in the 1.020-1.022 range usually. I think you're under pitching. I usually will rack a 1.100+ RIS wort onto roughly 3/4 of a yeast cake from a previous fermentation.
mtc
06/18/08 01:17 PM  
Re: terminal gravity on imperial stouts
If you want a lower FG, I agree with tankdeer that you should use a larger pitch rate. Maybe even letting the temp rise a bit towards the very end of primary would also help.

Most of the recipe/tech literature I've come across suggests a much higher FG than what you are after. I know Jamil, for example, suggests 1.030 for his. The general argument is that one wants a balance of sweetness and roastiness from the malts, and too dry a finish leads to the possibility of astringency. That said, I too, prefer a dry beer.

There are so many unfermentables in this style, plus the huge SG that it may be asking too much, especially of 1968, to get down that low.

tankdeer
06/18/08 02:12 PM  
Re: terminal gravity on imperial stouts
I agree that one generally wants a higher FG to balance everything out. But personally I find that in the low 1.020's I get a great balance of sweetness and roastiness without making it too thick. I like my big beers to sneak up on you, and a lower FG helps with that. ;-)
Mike T
06/18/08 02:18 PM  
Re: terminal gravity on imperial stouts
Are you treating your mash water? Any chance that all that dark malt is driving your pH lower than the enzymes like it?

Why not use a pound of a flavorful sugar? Iíve used dark candi syrup, heather honey, and unrefined sugars, all with good results in big dark beers.

mtc
06/18/08 02:51 PM  
Re: terminal gravity on imperial stouts
I've yet to meet an Imperial Stout that could sneak up on me, they are just too robust and outgoing in terms of flavor to hide what they are capable of.

How long are you aging your Imperial Stouts before serving, folks?

petec
06/18/08 03:56 PM  
Re: terminal gravity on imperial stouts
So I don't do any water adjustments but have made them using water over the years from several different locations. Current location uses San Francisco city water from hetchhetchy.

My latest RIS from several weeks ago does use upwards of 11% darker grains in it between choc and roasted barley along with a decent amount of specialB and crystal malts.

Using a entire yeast cake is a bit tough to do just in terms of wort/beer loss due to massive blowoff. 16 oz of thick slurry from a prior batch has been my current practice. I guess I should calculate out the appropriate amount sometime just to see how far off I am if at all.

I could go the sugar route but am just interested in how folks might drive them lower with allgrain and no sugar or if its just not that possible.

thanks,petec

petec
06/18/08 03:58 PM  
Re: terminal gravity on imperial stouts
I also batch sparge and concentrate the wort from 25 lbs of grain to yield 6 gallons of final wort postboil. This could possibly also be a source of tougher to ferment sugars I guess.

petec

Mike T
06/18/08 04:21 PM  
Re: terminal gravity on imperial stouts
There arenít many places in America that have enough carbonate in the water to counter that much dark malt. I also find that water adjustments take the harsh/acrid bite that sometimes accompanies highly roasted beers. I also enjoy a little extra sodium and chloride in the water, makes for a very smooth/malty beer (great unless, you are brewing a super hoppy RIS).

It could also certainly be the grain bill, that sounds like a good chunk of specialty malts, but mashing in the mid-140s should get you more than 70% AA with 1056.

Failing mash/recipe fixes you might try adding some US-05, that stuff can chew through just about anything. It recently took a barleywine I made from 1.115 to 1.018 (~7% crystal, mashed at 151).

tankdeer
06/18/08 04:52 PM  
Re: terminal gravity on imperial stouts
I find that a RIS can definitely sneak up on you. Not in the sense that you don't realize it's high in alcohol, but more in the sense that the alcohol presence is hidden, and the taste is such that you want to and can drink a couple of them. Deschutes The Abyss is a great example of that. It's rich and tasty, and you know it's strong, but it's drinkable enough to where you could have a couple and not be full. You'd be feeling it though. ;-)

For the record, my last RIS was 1.104 to 1.022. All grain, no sugar, mashed around 148 or so, and pitched onto 3/4 of a cake of WLP001. This was a 5.5 gallon batch and has been in the bottles about 14 months. I have only drank maybe 10 or less bottles. I've been wanting to brew another soon.

Brewing water was not treated; but my next one likely will be. At very least to ensure proper mash pH.

petec
06/18/08 05:04 PM  
Re: terminal gravity on imperial stouts
Good details on prior successes - thanks!

I've had barleywines go to 1.020 level but never RIS. The barleywines I've also added pure O2 at 12 hrs post pitch which is something I didn't do on the RIS since it was already rocking by then.

maybe I'll up the yeast amount next time on the RIS. thanks.petec

Seanywonton (Sean White)
06/19/08 12:43 PM  
Re: terminal gravity on imperial stouts
I think the real culprit here is probably a combination of the large total amount of specialty grains and your mashing temperature. You didn't post malt percentages or mash temp, but it would seem to be the reason why you can get a drier barleywine, but not a drier RIS.

Depending on your OG, amount of roasted grains, and IBU's, I think 1.022 - 1.030 would be a good target FG.

petec
06/19/08 02:10 PM  
Re: terminal gravity on imperial stouts
for the recent RIS that I'm referring to....... 2% crystal 40, 2% crystal 150, 4% specialB were the caramel malts. Mash temp was 147F. yeast was 16 fl oz of 1056 thick slurry. 2min pure O2 thru a siltered stone at pitching.

per the yeast calcs, I'm anywhere from proper pitch rate to underpitching by 50% if you go by 1-2 million/mL degP.

thanks. petec

ErikH
06/19/08 03:45 PM  
Re: terminal gravity on imperial stouts
Just to add a data point - my first IS was this year with WY1028 - OG: 1.091 / FG: 1.018. I was surprised by this apparent 80% attenuation, but then ferm temps were high at 71-72, plus we mashed a little low with an average temp of 147.

I would go with WY 1056 next time as the London yeast did add some fruitiness that, while not unpleasant, skews it from the target and does not show off the hops as well.

We did treat the water with 2 tsp of baking soda to address pH. All grain, modeled on the GD Oak-Aged Yeti, no sugars added.

petec
06/20/08 01:27 PM  
Re: terminal gravity on imperial stouts
For my recent RIS, I added 1 oz med toast american oak cubes and 1 oz med toast french oak cubes to the secondary carboy last night. Probably let it sit with them for maybe 2 weeks and then off into the keg it'll go. Steamed the cubes for 15 minutes prior to use to santize but not lose the oaky character.

I think it'll balance nicely with the FG numbers I was posting.

petec

tankdeer
06/20/08 02:24 PM  
Re: terminal gravity on imperial stouts
Good idea pete. In addition to adding a nice flavor, the tannins in the oak will help to give the impression of dryness. Which can work really well in a big beer like an RIS.
petec
07/11/08 04:59 PM  
Re: terminal gravity on imperial stouts
My RIS sat on the 2 oz med toast oak cubes (1 french and 1 american) for 3 weeks. FG was still 1.032 going into the keg.

No massive tannic oak notes so that is good. We'll see how it tastes in a few weeks all carb'd up.

petec

tankdeer
07/11/08 06:58 PM  
Re: terminal gravity on imperial stouts
Odd. That is a little on the high end.

I am actually brewing up an RIS tomorrow, so I'll chime in on the TG in a few weeks. I'm shooting for the 1.110 range for OG. (We'll see how my sometimes sporadic efficiency treats me tomorrow)

Seanywonton (Sean White)
07/12/08 10:22 AM  
Re: terminal gravity on imperial stouts
petec: Don't forget your roasted grains are also going to effect your F.G., not just crystal. The combination of these 2 could be the reason you are a little high in terminal gravity. But 1.032 down from 1.100 is not bad. It depends on the balance of the other factors of the beer. If your hopping rates and quantity of roasted grain are on the high side, it may be a very well-balanced beer.
BPotts
07/12/08 10:36 AM  
Re: terminal gravity on imperial stouts
That's what I was thinking, 1.032 down from 1.100 doesn't sound bad... There was an imperial stout recipe in zymurgy not too long ago that had a FG of 1.040 or something crazy like that. The beer I blended not too long ago, from 1/3 high grav flemish red and 2/3 imperial stout, has an FG of 1.035 or 1.038 or something. It's a little malty but that's supported by a lot of acid and oak flavors, and it works well for the beer. I enjoy my really strong stouts a little maltier anyway, If it gets too dry the roastiness can easily get over bearing.
tankdeer
07/14/08 11:23 AM  
Re: terminal gravity on imperial stouts
Brewed my stout on saturday. OG was 1.119. This thing is going to be a monster. It's chugging away real nice now though. I'll report back on the TG when I have it.
petec
07/14/08 01:58 PM  
Re: terminal gravity on imperial stouts
My roasted grains were about 11% and the IBUs were somewhere in the 70-80 range. On tasting sending the batch to keg, its not sweet. Balanced could be the right word. we'll see at carbonation in a few weeks.

cheers pete

petec
07/25/08 12:56 PM  
Re: terminal gravity on imperial stouts
While its not a real perfect comparison, I brewed a 1.100 all maris otter barleywine (racked yesetrday after 2 week primary) with similar mash temp and dough-in ratio to the RIS. It did have a lb of sugar in it though....... but anyways, it fermented down to 1.016 using US-05 pitched from a prior pale ale.

I'll have to try US-05 in my next RIS, but I think the heavy roasted grain use makes it a lot harder to get the ferment to go super dry in a RIS.

The US-05 used was a full cake so maybe that was it also. Its the lowest gravity I've ever gotten in a barleywine actually. Mine tend to hover around 1.020 FG.

Tank, how is your monster RIS doing? what yeast did you use?

petec

tankdeer
07/25/08 04:20 PM  
Re: terminal gravity on imperial stouts
<<Tank, how is your monster RIS doing? what yeast did you use?>>

I actually wrote myself a note to take a reading tonight. I'll let ya know what it's at. I used an entire cake of WLP001 although the fermentation wasn't as violent as I expected (Not necessarily a bad thing). I'm hoping for something in the 1.020-1.025 range myself.

tankdeer
07/25/08 11:41 PM  
Re: terminal gravity on imperial stouts
Well, I just checked it. It's only at 1.054 right now. It's still chugging, but fairly slowly. I had feared this as the yeast was of questionable viability. It was one of my first uses of a frozen aliquot of yeast. I pitched some US05 just in case. Hopefully it'll help it chug along. I am also going to warm it up a little. I've been keeping it around 66-68 so far. I'll post back when it's done-done.
tankdeer
08/13/08 10:49 PM  
Re: terminal gravity on imperial stouts
Well, I just racked it to a keg for long term aging. It's down to 1.043. Better, but still pretty crappy. Taste good, just too sweet. Probably will brew this again within the next couple months if this doesn't attenuate further. Might pitch some brett or do some blending to get it down a little.
 
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