Crystal malts are a staple in almost every beer recipe. Light crystal malt, like C-20, is used in pale ales, the darker C-120 can be used in stouts, and every recipe in between calls for some variety of crystal. Since crystal malts are among the few styles that do not need to be mashed, they are ideal for extract and partial-mash brewers to use as steeping malts.
Anyone can make this fabulously versatile malt at home. All it takes is any standard pale malt, some water and a few hours in the oven.
Crystal is a convenient brewer's malt because the carbohydrates in the grain are converted to sugars prior to roasting. This process not only makes it possible to use it as a steeping malt, but it also creates proteins that improve body and head retention. The sugars produced are not easily consumed by yeast, so they remain in the beer after it's fermented which increases sweetness, flavor and mouthfeel.
When you make crystal malt at home, you're not going to end up with a grain identical to what you buy in the store. The flavor ends up being a little more toasty and a little less sweet. The color is a bit harder to predict. Also, it's not a time-saving or a money-saving project. Instead, what you gain is flexibility and flavors that you won't be able to find in your local homebrew store. There are few varieties of Belgian crystal malt or crystal Marris Otter, and there is no commercial version of crystal Pilsner malt, as far as I know. So if you want the unique flavors provided by these base malts in crystal form, you'll have to make it yourself.
The process takes about a day, but it requires very little supervision. Newly made crystal malt tends to be a bit astringent, so it will need to age for a few weeks before you use it in a homebrew recipe. Commercial versions are typically aged about six weeks before distribution. For the home made version, plan on waiting two weeks for light crystal and six weeks for darker versions.
Soak the grain:
Before any cooking takes place, the grains need to be saturated in water to facilitate the conversion process. Start with 1 to 2 pounds of any variety of pale malt, place it in a large bowl and add just enough water to cover the surface. The grain can soak for anywhere from 3 to 12 hours.
Convert the grain:
Preheat your oven to the lowest setting it will go. Ovens that go as low as 170°F or 180°F are ideal, but it will work fine if you are at 200°F and leave the door slightly cracked open. Heap the wet grains on a baking pan so that they're about 2 inches deep. Don't spread them too thin yet, since the moisture in the center gives the enzymes a place to work. If you have a food thermometer, the goal is to keep the center of the grain pile between 145°F and 165°F.
This step is equivalent to making a mash. It's is the step that converts the starches inside the kernels into sugar, and so moisture and temperature are important. The grain should stay at this temperature for 1 to 2 hours. The longer end of that scale will allow the grain to get just slightly sweeter.
Dry the malt:
After the malt has been converted, it needs to be heated and dried. Turn the oven to 250°F, spread the malt around the pan so it's less than 1 inch thick and set the timer to 2 hours. Stir the malt around a couple times to prevent kernels from scorching and to ensure they dry evenly. Not only does this stage dry the malt to prepare for roasting, but it stops the enzymatic activity that was taking place during conversion.
Roast the malt:
When the grain is dry, turn the oven up to 350°F. This temperature will caramelize the sugar in the grain that was produced during conversion. Ten minutes at this temperature will produce a nice light crystal malt that can be substituted for C-10 or C-20, 30 minutes makes an amber colored grain close to C60, and a hour will make a dark brown crystal that's at least C-100. While the grain is roasting, check on it from time to time and stir in the kernels on the side of the pan that may be getting a more charred than the ones in the middle.
Once the roasting is done, remove the malt from the heat and let it cool. Store in a cool, dry place for 2 to 6 weeks, and then substitute the grain in for the appropriate colored crystal malt in any recipe.