Fermenting an Imperial Stout

For my next batch I want to brew an Imperial Stout. This will be the highest gravity beer (Estimated Original Gravity:1.081-85) that I have brewed and I have a few questions.

1) What should my fermentation schedule be? How long in the primary, how long in the secondary?

2) How do I get enough oxygen in my wort for the yeast? I do not have any aeration equipment.

3) My primary is a 6 gallon bucket, will I need a blow off tube?

1. Primary until you hit FG. "Secondary" on this board is often confused with what pro brewers call "bright tanks" which allow for more time for sediment, protein, and yeast to drop out and create a "pretty" beer. A true Secondary ferment is when you add more sugars/fruit/adjuncts after your primary fermentation has completed.

2. Best advice is to invest in an oxygen system. I have the one from Williams Brewing. If not, splash it into the fermentor and shake the bucket a bunch and just deal with a sub-optimal O2 saturation... nothing you can do about it w/o an aeration stone.

3. What is your batch size? Assuming 5 gallons, and your bucket being 6 or 6.5... you'll need a blowoff tube with almost 99% certainty.

4. unsolicited advice: Use Mr. Malty (www.mrmalty.com) to pitch the appropriate amount of yeast. Ferment the beer at the lower end of the range noted by the manufacturer. Invest in an aeration system (O2, sterile pump, etc.). Look into putting together a "swamp cooler", big beers generate lots of internal heat when the yeast gets going, it could be 10F over ambient.

Thank you for the input. I do have temp control so fermentation temp should not be a problem. I don't know if I understood the schedule advice although I appreciate the knowledge. You were recommending keeping in the primary vessel until I hit FG and then transferring to a secondary fermenter, correct? How long should the beer age In total? I'll look into the aeration system. I appreciate the advice.

What moviebrain is saying is that you should let your beer ferment until it is done and then chill it. There is no need for a secondary.

Once you get to your final gravity wait a day (or two) so the yeast can clean up any unwanted byproducts and then chill it. That is assuming that you are not wanting to stop the fermentation early to produce a sweeter beer.

I thought since it was a higher gravity beer it would need to age for a couple of months and thus need to be transferred off the trub but you are saying don't treat it differently. Am I mistaken about the extended aging or should this be done in the bottle rather than a fermenting vessel?

When I do high grav stuff, I aerate it with pure O2 (maybe 30 sec or so) at pitching and then again at about 18 hours after pitching. I bottle after about 4 weeks assuming its at FG, and then forget about it for 6-9 months.

JonM said:

When I do high grav stuff, I aerate it with pure O2 (maybe 30 sec or so) at pitching and then again at about 18 hours after pitching. I bottle after about 4 weeks assuming its at FG, and then forget about it for 6-9 months.

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Thanks guys. There is where my confusion started. I was assuming the 6-9 in the fermenter. Where do you get the o2 tank filled?

Oh and here's a trick if you don't have aeration equipment: the reason we aerate is because the yeast need it to reproduce. We use pure O2 because, for high grav beers, the yeast eed more O2 than there is in room air. So if you try to aerate using splashing, the yeast might not get enough O2 to finish the batch.

Solution? A big-arse starter. Also known as another batch. You can brew a 2.5 gallon (or whatever size you like) of an average grav oatmeal stout, bottle that, and then put your Imperial Stout on the yeast cake. The yeast in the cake will already be at (or probably above) the volume needed to ferment the big beer. In that case, no O2 needed. Cheers!

Amff said:

Thanks guys. There is where my confusion started. I was assuming the 6-9 in the fermenter. Where do you get the o2 tank filled?

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Most of us use the red Bernz-O-Matic tanks you get in the welding/brazing dept at the hardware store.

JonM said:

Oh and here's a trick if you don't have aeration equipment: the reason we aerate is because the yeast need it to reproduce. We use pure O2 because, for high grav beers, the yeast eed more O2 than there is in room air. So if you try to aerate using splashing, the yeast might not get enough O2 to finish the batch.

Solution? A big-arse starter. Also known as another batch. You can brew a 2.5 gallon (or whatever size you like) of an average grav oatmeal stout, bottle that, and then put your Imperial Stout on the yeast cake. The yeast in the cake will already be at (or probably above) the volume needed to ferment the big beer. In that case, no O2 needed. Cheers!

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Great advice. Thanks.

I just bottled a Russian Imperial Stout that turned out very good IMO so I figured I'd chime in. It was the brewers best RIS extract kit. I did not aerate, just splashed it as best I could when transferring into primary, I pitched a 1000 ml starter of White Labs 007. Used a three piece airlock for 24 hours until it started to blow off, then removed the cap and middle piece and attached a blow off hose to the center post. It was a VERY vigorous fermentation and blew off for around three days or so. Had my primary in a swamp cooler the whole time. It stayed in primary for four weeks and was still slowly creeping down to FG. at four weeks transferred to five gallon glass carboy to finish and bulk age for around three months. I bottled it a couple weeks ago and just tried one, it carbed nicely with a four ounce corn sugar prime. At this point the alcohol taste is still quite "hot", but I figure around New Years it will be perfect.

If you have an air compressor you can attach a sterile filter inline and just pump in ambient air. Doing it this way you never fully saturate the wort with too high a degree of oxygen. If you have never added oxygen before I would be careful. YOU CAN OVER OXYGENATE WITH PURE 02 VERY EASILY!!!! Too much oxygen is not only bad for your yeast health (it kills them), you will also be adding to the growth phase and all the yeast will eat more sugar, converting it to cellular components and in turn cut down on the available sugar to be converted to alcohol.

Shaking the **** out of your fermenter never hurt either.

DerekB said:

I just bottled a Russian Imperial Stout that turned out very good IMO so I figured I'd chime in. It was the brewers best RIS extract kit. I did not aerate, just splashed it as best I could when transferring into primary, I pitched a 1000 ml starter of White Labs 007. Used a three piece airlock for 24 hours until it started to blow off, then removed the cap and middle piece and attached a blow off hose to the center post. It was a VERY vigorous fermentation and blew off for around three days or so. Had my primary in a swamp cooler the whole time. It stayed in primary for four weeks and was still slowly creeping down to FG. at four weeks transferred to five gallon glass carboy to finish and bulk age for around three months. I bottled it a couple weeks ago and just tried one, it carbed nicely with a four ounce corn sugar prime. At this point the alcohol taste is still quite "hot", but I figure around New Years it will be perfect.

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DerekB said:

I just bottled a Russian Imperial Stout that turned out very good IMO so I figured I'd chime in. It was the brewers best RIS extract kit. I did not aerate, just splashed it as best I could when transferring into primary, I pitched a 1000 ml starter of White Labs 007. Used a three piece airlock for 24 hours until it started to blow off, then removed the cap and middle piece and attached a blow off hose to the center post. It was a VERY vigorous fermentation and blew off for around three days or so. Had my primary in a swamp cooler the whole time. It stayed in primary for four weeks and was still slowly creeping down to FG. at four weeks transferred to five gallon glass carboy to finish and bulk age for around three months. I bottled it a couple weeks ago and just tried one, it carbed nicely with a four ounce corn sugar prime. At this point the alcohol taste is still quite "hot", but I figure around New Years it will be perfect.

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Good to know. What about the yeast cake Jon mentioned. I am currently fermenting an IPA with WLP090. Kind of goes against the style but would racking onto the cake be a benefit or do you think it would give it a weird taste. If I did rack onto the cake should I pitch a 2L starter and just shake the **** out of it or would the cake be enough and ditch the starter. I don know if I can secure the o2 setup in time and I want this to be ready by march.

Amff said:

Good to know. What about the yeast cake Jon mentioned. I am currently fermenting an IPA with WLP090. Kind of goes against the style but would racking onto the cake be a benefit or do you think it would give it a weird taste. If I did rack onto the cake should I pitch a 2L starter and just shake the **** out of it or would the cake be enough and ditch the starter. I don know if I can secure the o2 setup in time and I want this to be ready by march.

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I'm no expert, but the WLP090 cake from your IPA should do fine with the imperial stout and if I'm not mistaken, you should just be able to rack onto the cake as its more yeast than any starter your likely to make, and I doubt you'd have to worry much about picking up any off flavors in the stout from the IPA. Maybe a bit more hoppiness? Anyone with more experience please feel free to correct me here, the above advice is just based on reading I've done and not actual experience.

You can rack onto the yeast no problem. Just shake the holy hell out of it to oxygenate. I would also let the cake warm up to room temp before you add the wort, that wSy you don't shock the yeast.

Amff said:

Thank you for the input. I do have temp control so fermentation temp should not be a problem. I don't know if I understood the schedule advice although I appreciate the knowledge. You were recommending keeping in the primary vessel until I hit FG and then transferring to a secondary fermenter, correct? How long should the beer age In total? I'll look into the aeration system. I appreciate the advice.

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Regarding Primary until FG: yes. The goal here is to leave the beer in maximum contact with the bulk of the yeast until all those sugars have become beer. Only after that job is done would you rack off the yeast. You can "secondary" your RIS bulk for a few months or just bottle it and open one every 3-4 weeks until it is awesome. Since stouts are so dark, you don't need to age it for cosmetic reasons just flavor reasons. Proper pitch rates, temperature control, and good ingredients will shorten the time from grain to glass significantly.

I don't aerate. If you're lazy and cheap like me, you can get a wine degasser wand, attach it to your cordless drill, and whip the hell out of the wort before adding the yeast. I find this to be easier and more effective than sloshing the fermenter around.

EternalStudent said:

YOU CAN OVER OXYGENATE WITH PURE 02 VERY EASILY!!!! .

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No, you can't.

As for the aeration, I have tried the O2 method on and off for the last few years in conjunction with just running my cooled wort through a screen. I have not really noticed a big difference in flavor, fermentabilty, or time to initial fermentation. I have no scientific evidence, but I brew between 200 and 300 gallons a year, many of the same popular beer over and over. Just what I have noticed.
As for the secondary "clearing vessel" go for it, I brew my RIS in February and bottle in October or November. I add some champagne yeast to the batch some time mid summer, just to eat up any un-fermented sugars if there is any. (Haven't had any the last three years.) It seems to hang around just a bit longer for the long storage in the secondary to have something to ferment the bottling sugar in the fall. Again, no science or proof, just something I have always done and it seems to work well. I really don't want to change anything on this "once a year" beer that is quite expensive.

Good luck and let us know how it works out!

JonM


Yes you can. I'm a pro brewer buddy. Do some research.

'k.

I have been brewing for a little over a year now. I've read the books and magazines but this forum has been the most educational. It really outlines the art in brewing with all the different methods. This thread has given me at least a tentative game plan. A couple more questions, if I choose to age in a secondary vessel for a few months will I need to repitch some yeast at bottling time and after the primary fermentation is complete how important is it to hold the temp? If my ambient temp is in the low to mid 70's should that be ok for the aging process.

Amff said:

I have been brewing for a little over a year now. I've read the books and magazines but this forum has been the most educational. It really outlines the art in brewing with all the different methods. This thread has given me at least a tentative game plan. A couple more questions, if I choose to age in a secondary vessel for a few months will I need to repitch some yeast at bottling time and after the primary fermentation is complete how important is it to hold the temp? If my ambient temp is in the low to mid 70's should that be ok for the aging process.

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I'd say you'd be ok for around 3-4 months in a high gravity brew bulk aging at a steady "cellar" temp of 45-55F without repitching. If the temp drops to near freezing or is above 70 for an extended period of time you may shock what's left between temp, time, and abv% and require a bit of fresh yeast to carb a bottle.

I'm not saying it wouldn't carb, I'm just saying for a 1.080-ish beer that you're putting a bit of money and time into, what's $1 for a pack of dry yeast?

Not trying to thread jack here, just a question I had that might help the OP....

When I brew, I typically end up with 3-4 gallons in my brew pot, and I top off to 5gal in carboy/bucket with water from my faucet. When I do this, I use the faucet sprayer to fill. This seems to aerate the wort pretty well in my opinion, am I wrong? I've never used pure O2, and I've turned out some outstanding high gravity beers. I've done this in both carboys and buckets and seem to end up with the same results. I'm sure there's some science behind this, and which works better and why....

krebs119 said:

Not trying to thread jack here, just a question I had that might help the OP....

When I brew, I typically end up with 3-4 gallons in my brew pot, and I top off to 5gal in carboy/bucket with water from my faucet. When I do this, I use the faucet sprayer to fill. This seems to aerate the wort pretty well in my opinion, am I wrong? I've never used pure O2, and I've turned out some outstanding high gravity beers. I've done this in both carboys and buckets and seem to end up with the same results. I'm sure there's some science behind this, and which works better and why....

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The short answer is, "If it works for you, cool."

The longer answer is, "Adding unboiled/untreated/unpasturized water to your sugary wort is a recipe for sadness and infection."

Faucets aren't generally sanitary, but that's because water is not a nutrient rich environment and the few bugs that aren't killed by the city water treatment plant or the water additives of chlorine and chloramine and whatnot can be easily handled by your immune system.

Wort can wake them up and give them an amusement park to play in.

I'm not saying it happens all the time. I'm not even saying it's likely. I'm saying that what you're suggesting is not "best practice" and when I need to top up I only do so with cooled pre-boiled water or store bought water jugs that've been dipped in starsan.

Yeah, I'm aware of that, that wasn't really answering my question though. I've not yet had an infection from doing this (over 60 brews in now). My question was more regarding how much oxygen I'm adding to the wort by doing this.

Sorry about that. Spraying in water, just like shaking or stirring or sloshing will never get you more than 8ppm O2 (which takes around 5 minutes of shaking or stirring).

Depending on how much yeast you pitch and how high your gravity is that may or may not be sufficient.

Did you make good beer doing that? Put that in the success category. Could it have finished cleaner and/or faster? Maybe. Then again, under/over pitching yeast, fermenting hotter or colder, and other factors may stress your yeast in such a way that it creates the flavor you're looking for, as can under or over oxygenating your wort.

Do what you need to do to make the beer you like drinking =)

Ok so I racked the imperial stout on the yeast cake from my IPA and saw activity within the hour. Thanks for that idea. When putting beer on an existing cake do you try and clean the sediment from the prior fermentation off the sides? I chose to try. Also, moviebrain suggested to wait to I reached fg before I transferred to a secondary. I have only used a secondary once and I transferred while there was still some activity so the co2 could purge the oxygen. If I wait to fg should I just hit the headspace with some co2 and quickly cap it off? Just curious what technique people use to blanket the co2 on top when using a secondary.

When you transfer to a secondary, the best thing to do would be to minimize headspace. If you brewed 5 gallons, put it in a 5 gallon carboy and try to fill it up to the neck. Doing so leaves very little surface area exposed to oxygen (little neck vs bulk of the carboy's space).

Just because the yeast is done munching on the sugar doesn't mean it won't keep offgassing just a little bit. There is a small amount of CO2 in the beer leftover from fermentation that will slowly come out of solution while you're racking it too.

Good luck!