A 2-gallon and a 3-gallon beverage cooler. The 2-gallon (~8-L) cooler can be used to mash 4.0 lbs. (1.8 kg) of grain. The 3-gallon (11-L) cooler can be used to mash 6.0 lbs. (2.7 kg) of grain.

There are many different ways to approach a partial mash. In two previous articles, I discussed the rationale for partial mashing and one method of performing a partial mash — “steeping” the grains in a grain bag, then placing them in a colander over the brewpot and rinsing them. This works well for partial mashes with amounts of grain up to about 4 lbs. (~2 kg). Above that amount, the colander method becomes more difficult. Unless you have an enormous colander, the bag will overflow it and you’re more likely to drip wort everywhere. For larger partial mashes, I like to use what I call countertop partial mashing. Countertop partial mashing uses either a 2-gallon (~ 8-L) or 3-gallon (~11-L) beverage cooler as the lauter tun, the vessel that holds the mash while the sweet wort is separated from the spent grains.

An insulated beverage cooler — the type with a spigot at the bottom, for holding cold or hot drinks at outdoor events — can be used as either just the lauter tun or as both the mash and lauter tun. For coolers up to 5 gallons (~20 L), simply lining them with a large steeping bag is sufficient to separate the wort from the spent grains. (If you want to get fancy, you could install a manifold, as with a full-sized cooler-based lauter tun.) This method delivers between 3 and 4 gallons (~10–15 L) of wort, to which malt extract can be added. This wort can be boiled on a stovetop, the chilled, transferred to a fermenter and diluted with cool water to 5 gallons (19 L) of wort.

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