Recipe: Human Robot Polotmavy 12°

Andrew Foss, head brewer at lager-heavy Human Robot in Philadelphia, shares this recipe for their “half-dark” Czech-style lager—now a popular year-rounder for them, born when Foss wanted to brew a tmavý. “But I was short on roasted malt that day,” he says, “and a staple beer in our lineup was created.”

“Decoction brewing gives the brewer excellent control over the beer’s attenuation and overall malt profile,” Foss says. “The method used here is known as ‘enhanced decoction,’ and it gives the brewer maximum control of timing the temperature rises in the main mash.”

ALL-GRAIN

Batch size: 5 gallons (19 liters)
Brewhouse efficiency: 72%
OG: 1.051
FG: 1.012
IBUs: 25
ABV: 5%

[PAYWALL] MALT/GRAIN BILL
7.2 lb (3.3 kg) Czech floor-malted pilsner
2.2 lb (1 kg) Munich
3 oz (85 g) Weyermann Carafa Special III

HOPS SCHEDULE
0.3 oz (9 g) Saaz at first wort [4 IBUs]
0.3 oz (9 g) Magnum at 60 minutes [13 IBUs]
1.6 oz (45 g) Saaz at 15 minutes [8 IBUs]

YEAST
Fermentis SafLager W-34/70, Imperial L13 Global, or similar

DIRECTIONS
Mill the grains and mash at 140°F (60°C) for 20 minutes. Pull half the mash volume to a preheated kettle for a decoction: Raise to 158°F (70°C), hold there 15 minutes, then bring it to a boil for 20 minutes. Fold one-quarter to one-half of the decocted portion back into the main mash, targeting a mash temperature of 154–162°F (68–72°C); avoid stirring vigorously. Meanwhile, continue boiling the rest of the decocted portion for another 20 minutes, then fold that portion back into the main mash, targeting a temperature of 169–172°F (76–78°C). (If you reach that temperature before all the mash is combined, don’t worry—just allow the rest of the decoction to cool a few minutes, then add it to the top, trying not to disturb the mash below.)

Recirculate until the runnings are clear, then run off into the kettle with the first-wort hops. Sparge and top up as necessary to get about 6 gallons (23 liters) of wort, depending on your evaporation rate. Boil for 75 minutes, adding the remaining hops according to the schedule. After the boil, chill to about 43°F (6°C), aerate the wort, and pitch the yeast. Ferment at 43°F (6°C), allowing a rise to 48–51°F (9–10.5°C) as fermentation peaks. If you have a spunding valve, attach it and set to 12–13 psi, conditioning at 39–41°F (4–5°C) for about 3 weeks—by that point, the beer should be fully carbonated and free of diacetyl. Crash to 32°F (0°C) for a few days and transfer to a purged keg for serving.

BREWER’S NOTES
Base malt: We typically use Raven Pilsen, but we’ve also had great results with Weyermann and Sekado. In place of the Munich, we’ve also used Weyermann Floor-Malted Bohemian Dark.

Roast malt: In lieu of the Carafa III, you could use any dark, roasted grain to dial in your color. Note that milling dramatically affects the color; it’s a good idea to have a little extra on hand. If the beer seems too pale at vorlauf, add a few more ounces to darken.

Decoction: A 3:1 water-grain ratio is a good place to start. Target a mash pH of 5.2–5.4; we use lactic acid to adjust. If you need to use American or German pils malt instead of floor-malted, shorten the first mash rest to 10 minutes. If the beer comes out too dry, play with the mash schedule before resorting to caramel/crystal malts. Modern malt—even floor-malted—is very well modified, and your tools to control attenuation are time and temperature.