Decoction mashing is a traditional technique in central European brewing which produces the deliciously malty flavors for which German beers are best known. (It can also get lovely results in other malt-forward styles such as Scottish ales.) While many German breweries have been moving away from using it, especially for their palest beers, on a homebrew scale it is an easy way to impart this flavor into your beer. The essence of decoction mashing is to boil some of your mash, grains and all, and then combine it with the rest (which has not been boiled) to reach desired rest temperatures. It's common to repeat this process two or three times to reach several desired temperature ranges.
Unfortunately, most homebrewers are put off by decoction mashing, and for good reason - traditional decoction mash methods are challenging and very time-consuming, and abbreviated ones don't cook quite as much of that delicious melanoidin flavor into the beer, effectively compromising between a decoction mash and a more typical infusion mash.
The Schmitz process is a relatively modern variant on the decoction mash that develops a very full flavor while being faster and easier than a classic double or triple decoction mash. As long as you are willing to stand by the stove stirring for a while, this is your path to classic German styles.
Step 1: Assemble Supplies
- Your brewing kettle.
- Another decently large pot (I'm using the three-gallon one I brew extract beers in; if you are doing this as the mashed part of a partial-mash beer, you could make do with a large saucepan).
- A cooking thermometer, ideally one with a probe.
- A mash tun. I actually don't have a dedicated mash tun even though I brew almost entirely all-grain beer; you don't need this to be as insulated as some people's, and I find a bottling bucket with a spigot, a steamer insert that fits inside and keeps things off the spigot hole, and a large pillowcase do the job nicely.
- A long-handled spoon that can reach all the way to the bottom of your kettle.
- Something (I like a large Pyrex measuring cup) to transfer hot liquid from one pot to the other.
- Your ingredients.
Step 2: Start Cooking Grains
Add hot water (ideally hot enough to hit about 120 degrees, but frankly I've never had a problem using hot tap water at this stage) to cover them, up to a depth of an inch or two. Put the thermometer probe in and set the alarm (if it has one) to 140. Then, turn on the stove.
Any time you aren't stirring the mash, you're going to want it to be covered, but you should stir it frequently. Make sure you stir all the way to the bottom of the kettle or some of your grains will probably stick and burn. (You'll also get a more accurate sense of the temperature as you stir.)
Step 3: Separate Liquid
Classically you would try to hold this liquid at just under a conversion temperature, but I don't bother. It does have to stay hot, which frankly it'll do just fine on its own.
Step 4: Boil Grains
Take it off the heat, and stick the thermometer probe in. Keep stirring periodically to get good temperature readings.
Step 5: Conversion Rest
I typically let my mash rest at 155 for 20 minutes to convert the starches into sugars. You want it no hotter than 158 (which will denature the amylase enzyme) and if it's colder you will want it to sit a bit longer. (If it's below about 145, add boiling water to bring the temperature up.)
I know I'm being far more imprecise here than any German brewery would be comfortable with, but this is supposed to be the easy version and the truth is as long as you get the grains (which have most of the thermal mass) down to 160 and the liquid is still hot, you're going to get good results out of a 20-minute rest.
Step 6: Brew Your Beer!
(For the curious, the recipe being made in the photographs is first-wort hopped with one ounce of Aramis hops, a recently-developed European strain that is about 8% alpha acid. At the boil, I added a touch of Irish moss as well, for clarity.)