Partial mashing is a method of wort production in which the brewer produces some of his wort from a mash — as an all-grain brewer would do — but supplements it with malt extract. In practice, it is usually used in conjunction with a partial wort boil, so that it is similar to the common malt-extract-plus-steeping-grains method. For extract brewers who don’t have the space for a full all-grain set-up, or outdoor all-grain brewers who occasionally wish to come in from the heat or cold, it is method of brewing that is more flexible — and I would argue produces higher quality beer — than the normal malt-extract-plus-steeping-grains methods.
There are numerous different ways a homebrewer can employ partial mashing. I have written about one method that involves mashing in your brewpot and another that I devised called countertop partial mashing. No matter how you partial mash, there are options that you may be able to take. When I partial mash, I like to use as much grains and as little extract as possible. (Malt extract is more expensive than malted grains; additionally, I think wort produced from grains is more aromatic.)
One way to get as much grain in your formulation as possible is to mash the grains that need to be mashed, and steep those that do not. In my countertop partial mash method, the cooler used to mash the grains will only hold so much malt. In recipes with a substantial amount of steep-able grains, I like to fill the cooler mash tun with the base grains, and steep the other grains, such as crystal malts or roasted grains. Here’s an example of that method, using my Firefly ESB as an example. (I took the same approach with my T-34 Stout recipe.)
In this recipe, you get a lot of flavor and aroma from the English pale ale malt — and the enzymes from the partial mash will work on the starches in the flaked maize. The caramel flavor in the brew will come from crystal malts that are steeped in your brewpot while the base grain and maize are mashing.
Firefly ESB
by Chris Colby
Partial mash; English units
DESCRIPTION
A slightly hoppier rendition of a homebrew Fullers ESB clone. The beer has a malty character, with some caramel flavor, balanced by 40 IBUs of hop bitterness. The aroma of Goldings hops completes the beer.
INGREDIENTS (for 5 gallons)
Malts and Grain (for an OG of 1.060 at 70% extract efficiency and 15 SRM)
2 lb. 14 oz. English 2-row pale ale malt
1.25 lb. flaked maize
1 lb. 2 oz. crystal malt (60 °L)
3 lb. 10 oz. light dried malt extract
Hops (for 40 IBU total)
Target hops (35 IBU)
(0.93 oz. at 10% alpha acids, boiled for 60 mins)
Goldings hops (5 IBU)
(0.75 oz. at 5% alpha acids, boiled for 15 mins)
Goldings hops (0 IBU)
(0.75 oz., dry hop)
Yeast (for an FG of 1.014 and 5.9% ABV)
Wyeast 1968 (London ESB) or White Labs WLP002 (English Ale) yeast
(2-qt. yeast starter)
Other
1 tsp. Irish moss (boiled for 15 mins)
PROCEDURES
Mash the pale ale malt and flaked maize at 153 °F in 5.5 qts. of water. Put the crystal malt in a steeping bag and place it in your brewpot. Add a gallon of water to your brewpot and steep the crystal malt at around 153 °F. Let the mash rest for 60 minutes. Recirculate and collect about 2.5 gallons wort. Collect the wort slowly so that it takes about an hour. The partial mash wort and “grain tea” from steeping the crystal malt should equal roughly 3.5 gallons. When wort collection is finished, remove the steeping bag from the brewpot, add roughly one third of the malt extract, and bring the wort to a boil. Boil the wort for 60 minutes, adding hops and Irish moss at times indicated. Stir in remaining malt extract with 10 minutes left in the boil. Chill wort and transfer to fermenter. Top up to 5.0 gallons with cool water. Aerate wort and pitch yeast. Ferment at 68 °F.
Firefly ESB
by Chris Colby
Partial mash; metric units
INGREDIENTS (for 19 L)
Malts and Grain (for an OG of 1.060 at 70% extract efficiency and 15 SRM)
1.3 kg English 2-row pale ale malt
0.57 kg flaked maize
0.51 kg crystal malt (60 °L)
1.6 kg light dried malt extract
Hops (for 40 IBU total)
Target hops (35 IBU)
(26 g at 10% alpha acids, boiled for 60 mins)
Goldings hops (5 IBU)
(21 g at 5% alpha acids, boiled for 15 mins)
Goldings hops (0 IBU)
(21 g, dry hop)
Yeast (for an FG of 1.014 and 5.9% ABV)
Wyeast 1968 (London ESB) or White Labs WLP002 (English Ale) yeast
(2-L yeast starter)
Other
1 tsp. Irish moss (boiled for 15 mins)
PROCEDURES
Mash the pale ale malt and flaked maize at 67 °C in 5.2 L of water. Put the crystal malt in a steeping bag and place it in your brewpot. Add 4 L of water to your brewpot and steep the crystal malt at around 67 °C. Let the mash rest for 60 minutes. Recirculate and collect about 9.5 L wort. Collect the wort slowly so that it takes about an hour. The partial mash wort and “grain tea” from steeping the crystal malt should equal roughly 13 L. When wort collection is finished, remove the steeping bag from the brewpot, add roughly one third of the malt extract, and bring the wort to a boil. Boil the wort for 60 minutes, adding hops and Irish moss at times indicated. Stir in remaining malt extract with 10 minutes left in the boil. Chill wort and transfer to fermenter. Top up to 19 L with cool water. Aerate wort and pitch yeast. Ferment at 20 °C.
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