This is the seventh article in this series on Russian imperial stouts.
Whenever you brew a big beer, there are several options for wort collection. One of them is to only collect the first wort, or the first wort and a limited amount of sparged wort. That way, you have high-gravity wort that does not need to be boiled for an extended period to hit your target OG and volume. In order to utilize this method of wort production, however, you must add more grain to your mash tun to compensate for the loss in extract efficiency.
Many times, there are enough sugars left over in the grain bed that you can brew a second beer. Brewing a second beer from a Russian imperial stout grist poses two types of challenges – the usual challenges associated with brewing a second beer, and those challenges specific to brewing a second beer from a partially-spent Russian imperial stout grist.
Challenges
The usual challenges are that the remaining wort in the grain bed is higher in pH, and lower in protein and sugar. Also, much of the malt character has been rinsed from the grain husks. If you brew a beer only from second runnings, or wort collected late in the sparge, it tends to make non-malty, and possibly astringent, beer.
The usual solutions to this are to add malt extract to the wort, blend some strong wort in with the weaker wort, or add fresh malt to the mash. (Or, some combination of these.) Adding malt extract fixes the pH problem, but does little to improve the malt aroma. Blending some first wort in with your second runnings works great, but lowers the yield on your big beer. Likewise, adding fresh malt to the mash works great, but it requires more space in your mash tun. (See my article, “Brewing a Second Beer,” for general information on second beers.)
One challenge specific to making a second beer from a partially-spent Russian imperial stout grist is that you were limited in the type of beer you can make. It has to be a fairly dark, roast-y beer. In addition, the large percentage of dark malt increases the risk of astringency, which is already a common problem in second beers.
One Solution
Here, I will present one solution for making a second beer from a Russian imperial stout grist. Basically, the partially-spent grain bed will be refreshed by adding some fresh malt, and malt extract will be used to boost the gravity of the second wort a bit. The second beer will be similar to a dry stout. This will assume that the homebrewer has a fairly common set up for making 5.0-gallon (19-L) batches — a 10-gallon (38-L) mash tun and 10-gallon (38-L) kettle. You can easily scale this idea to other sized vessels.
Start with a 5.0-gallon (19-L) Russian imperial stout recipe formulated to be brewed from a fully-sparged grain bed. For example, my T-34 Stout recipe will work. Add pale malt to the recipe such that your mash tun will be full, or nearly so. If you have a 10-gallon (38-L) mash tun with a false bottom, you should be able to mash at least 24 lb. (11 kg) of grain at a mash thickness of 1.25 qt./lb. (2.6 L/kg).
Mash in, but withhold 1.5 lb. (0.68 kg) of dark grains until end of mash. Stir them into the top layer of the mash for the last 15 minutes. Recirculate briefly, but don’t mash out. Keep the grain bed at mash temperature. Run off the first wort, which should be approximately 4 gallons (15 L) at around SG 1.096, then collect 2.0–2.5 gallons (7.6–9.5 L) of sparged wort. This way you will have enough wort volume for a 60–90 minute boil. You can collect the wort either by batch sparging (with a small, single addition of sparge water) or by simply collecting the first 6.0–6.5 gallons (23–25 L) of wort if you fly sparge. (If you batch sparge, rehydrate the grain bed before proceeding.) Proceed with brewing the Russian imperial stout as you normally would.
Now you have a partially-spent grain bed and a full mash tun at mash temperature. Scoop out the top layer of dark grains — roughly the equivalent of the 1.5 lb. (0.68 kg) of dark grains you capped the mash with. Replace this with roughly a pound of (fresh, crushed) English pale malt and roughly 0.50 lb. (0.23 kg) of roasted barley (500 °L). This will “freshen up” the grain bed a bit, adding some malt aroma and dark grain character. Stir the fresh grains into the top layers of the grain bed and let them mash while you conduct the Russian imperial stout boil.
Once the Russian imperial stout wort is boiled, cooled, and trasnferred to the fermenter, quickly clean the kettle and begin running off the wort for the second beer. Given that this is going to be a long brew day, you might want to rush wort collection a bit if you fly sparge.
Collect 6.0–6.5 gallons (23–25 L) of wort. This is less than you could collect, but it will allow you to only spend 60–90 minutes boiling. In addition, you will avoid collecting the final runnings, which would be the most astringent. From this point forward, boil the wort and proceed as if you were brewing a dry stout. Use a hop schedule appropriate for a dry stout. Near the end of the boil, check the wort density and add malt extract as needed to hit a reasonable specific gravity. You should need at most 2.0 lb. (0.91 kg) of dried light malt extract to reach the target range for a dry stout.
When you’re done, enjoy a well-earned homebrew. You’ve extended your brew day by at least a couple hours, but you’ve got a Russian imperial stout fermenting as well as a very respectable dry stout.
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When I brewed my Black Friday RIS, I used the partigyle method. My second beer was a sweet stout by adding a pound of lactose. I had late hopped my RIS, so I used those spent hops (in a bag) for bittering the sweet stout. It worked out perfectly.
Sweet!