Malting converts starch in grains to sugars and enables a Maillard reaction, the process responsible for caramelization. Caramelization of barley corresponds to the drying time and drying temperature during malting; the higher the temperature at which the grains dry, the darker the malt and therefore the beer. Conversely, the lower the temperature that the grains dry at, the lighter the malt and color of the beer. Malt a 1-pound test batch before you malt everything you have if you're new at malting your own barley. Record the drying times and reference them when drying a large batch.
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Check the barley for broken and discolored grains and discard any you find. Transfer the barley to a sink or container and cover it with several inches of water. If testing the barley before malting the whole batch, weigh and soak only 1 pound of it.
Agitate the barley in the water for a few minutes and let it settle; skim the chaff off the water surface with a small mesh strainer. Strain the grains in a colander and rinse them under cool running water.
Pour the grains in a food container and cover them with 2 inches of cold water. Steep the grains for 8 hours and drain them; stir the grains in the container.
Set the grains aside for 8 hours; then cover them again with 2 inches of water. Soak the grains again for 8 hours and drain them for 15 minutes in a colander.
Line a baking sheet with a few layers of paper towels and spread the barley grains on them in an even layer. Slide the baking sheet in a black plastic bag and tie it off.
Place the bagged barley in a 60-degree-Fahrenheit room for five days or until the main white shoot, or acrospire, measures about 3/4 the length of the barley grain. The 1-pound test batch should weigh 24 ounces after it germinates.
Transfer the germinated barley, now known as green malt, to a baking sheet and set it on the middle rack of the oven. Turn on the oven light and dry the green malt for about 24 hours.
If testing, the 1-pound test batch should weigh 18 ounces. Record the exact amount of time it took for the test batch to reach 18 ounces so you know how long to dry a full batch.
Use chemical- and pesticide-free barley.
To make crystal malt, dry the grains for 1 hour at 212 F instead of 24 hours with the oven light.
To make Munich malt, toast the grains at 350 F until dark brown, or about 10 minutes if malting less than 1 pound, and for 20 to 30 minutes if malting 1 pound or more.
If you want the grain very dark, or nearly black, wrap it in aluminum foil and cook it on an outdoor grill until it turns the desired color. Making dark malt creates too much smoke to do indoors.