American Imperial Stout
All-Grain Recipe
(5 gallons/19 L, all-grain)
OG = 1.130 FG = 1.040
IBU = 60 SRM = 86 ABV = 12%
Our imperial oatmeal stout takes big and bold to the next level. This is a double mashed stout using an intricate malt bill with a lower percentage of base malt and the addition of rye malt as well as de-husked and debittered black malt. This helps to prevent introducing any ashy, smoke, or tannic character to the beer. The resulting beer is a massive imperial stout that will last for years in your cellar.
Ingredients
14.5 lbs. (6.6 kg) 2-row malted barley (55%)
2.6 lbs. (1.2 kg) flaked oats (10%)
1 lb. (0.45 kg) Munich dark malt (3.5%)
1.7 lbs. (0.77 kg) Carafa® Special III malt (6.5%)
1.7 lbs. (0.77 kg) chocolate rye malt (6.5%)
13 oz. (370 g) roasted barley (3%)
1.7 lbs. (0.77 kg) crystal rye malt (75 °L) (6.5%)
2.4 lbs. (1.1 kg) brown sugar (9%)
19 AAU Warrior hops (90 min.) (1.25 oz./35 g at 15% alpha acids)
1 tsp. yeast nutrient (10 min.)
1⁄2 Whirlfloc tablet (10 min.)
White Labs WLP090 (San Diego Super Strain), Wyeast 1728 (Scottish Ale), or SafAle US-05 yeast
2⁄3 cup corn sugar (if priming)
Step by Step
If starting with soft or reverse osmosis water, add 4 g calcium carbonate per 5 gallons (19 L) of strike water.
This beer is double mashed, meaning you will be mashing twice to get your kettle up to volume. If your mash tun is oversized and can handle it as a single mash, then go that route. Also, the wort will be boiled for 3–4 hours, so whether you double mash or not, be prepared for a long brew day. Knowing your system’s average boil-off rate is helpful to know how much wort to collect in the kettle prior to boiling.
We are essentially looking for just the first runnings to create a monster of a beer. If you are double mashing, mash half the grains in 6 gallons (23 L) of strike water to achieve a mash temperature of 148 °F (64 °C). After the mash is complete, run off to the kettle to about half the total volume required, sparging only if the volume is short. Repeat with the second round of grains to reach full pre-boil kettle volume. An extended boil along with the addition of brown sugar will help boost your gravity to 1.130. It is a good idea to take wort gravity readings over the course of the boil on the hour to monitor how close the wort is to hitting the 1.130 gravity. Add the hops and brown sugar during the final 90 minutes of the boil. Make sure to add more yeast nutrient than normal during the boil.
Your yeast pitch should be 5–6 times the normal pitch rate and be sure to aerate the wort if using a liquid strain or re-pitching yeast. Ferment at 66 °F (19 °C). Note that fermentation temperature can run quite high if not controlled. Keep the beer several degrees below recommended fermentation temperature if using ambient air temperature as the control. Warm up to 72 °F (21 °C) once fermentation begins to show noticeable signs of slowing. Fermentation will take 10–14 days total. Allow at least one month to condition at 55–60 °F (13–16 °C) after either racking off the yeast or dropping yeast from the bottom of the cone.
Transfer to a serving keg or bottle and prime with sugar targeting 2.3 volumes CO2.
Partial Mash Recipe
With this much specialty grain, brew-in-a-bag is the way to go. Swap out 12 lbs. (5.4 kg) of the 2-row pale malt for 6.25 lbs. (2.8 kg) extra light dried malt extract. Mash the crushed pale and dark Munich malts and flaked oats in a large brewing bag in 6 gallons (23 L) of water at 148 °F (64 °C). Hold at this temperature for 45 minutes. Add the remaining crushed grains and steep an additional 15 minutes. Remove grains. Top up the kettle to 6.5 gallons (25 L) with water. Off heat add the dried malt extract. Once fully dissolved, bring wort to a boil and boil for 75 minutes adding hops at the beginning of the boil. Follow the all-grain recipe for fermentation and packaging instructions.
