A Craft Beer & Brewing Magazine reader recently asked us the following question:
I’ve heard of a process where you mill your grain while wet? How would you do this, and what is the purpose?
Wet-grain milling, also known by the more formal term “conditioned milling,” is a method that can improve the condition of the crushed grain and reduce the chance of a stuck sparge. Done properly, it produces larger pieces of intact grain husk with less grain powder, resulting in good mash efficiency and a better filter bed for the sparge. It is primarily used for beers with a large portion of non-barley adjuncts.
The goal in wet milling is to raise the moisture content of the grain about 20–30 percent using steam or hot water spray before milling the grains wet. You should not attempt this unless you have a dual-roller grain mill because other grain mills, such as the “Corona”-style mills, will get gummed up with the wet grains.
The commercial method for conditioned milling is to steam the malt before milling. Hombrewers have two options: a steam method and another using hot water to hydrate the malt.
You can simulate the commercial “steam” method using some boiling water with a false bottom or a pot designed to steam vegetables. It’s generally easiest to get the water to a boil and bag the grains in batches if needed. Steam the grain for about 90 seconds, stir it gently, and then quickly mill it while it is still hot.
The other alternative is to spray hot water over the grains to hydrate them. I recommend using a small amount of grain at a time spread somewhat thinly over a false bottom. Spray water heated to 158°F (70°C) over the grain bed for about 60 seconds, allowing the excess to drain through the false bottom. Let the grain sit for 1–2 minutes to absorb some of the water and then quickly mill it.
If the grain doesn’t mill cleanly or the mill gets gummed, then the grain is too wet. Reduce the moisture level by reducing the steam time or hot spray exposure on the next batch of grain.
I will mention that wet milling is really not needed for most malted barley beers. If your grain mill is set properly, you can mill dry malt and brew with it without going through the extra steps of wet milling. Wet milling is most appropriate on beers that have a higher proportion of sticky non-barley adjuncts such as flaked barley or wheat that could lead to a stuck sparge.
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