Steeping some crushed grains in your brewing water is a common way for extract brewers to add flavors and colors to their brews. However, not every grain found at your local homebrew shop can be steeped. Some must be mashed. Steeping and mashing are similar processes if a homebrewer performs a partial mash. (A partial mash is a mash that supplies only a portion of a beer's fermentables. The rest is supplied by malt extract.) Steeping and partial mashing are not, however, identical processes and knowing which grains to steep and which need to be mashed will lead you to produce better malt extract-based beers.
What's the Difference?
Steeping is the process of soaking crushed grains in hot water to extract flavor and color components. Mashing is the process of soaking crushed grains in hot water to activate enzymes within them. The enzymes catalyze the conversion of starches into sugars. In the process, flavor and color components are also extracted. In both cases we soak the grains in hot water. The difference is whether or not we are activating starch-converting enzymes.
It's All About the Grains
Whether or not a grain can be steeped depends on how it was malted. Grains that have been stewed during malting can be steeped. Likewise, grains that have been kilned at high temperatures can also be steeped.
The most commonly steeped malts are the crystal malts (also called caramel malts). These grains are stewed during malting, then kilned to colors ranging from 10–180 °L. They lend a reddish color and sweet caramel-like flavor to your beer. Most of the starch in these grains is converted to sugar during stewing.
Grains that are kilned at higher temperatures or for longer periods — such as chocolate malt — can also be steeped. Roasted malts tend to be darker than crystal malts and give a darker color and sharper flavor.
Malts that are not stewed or highly-kilned must be mashed. These malts are called base malts. Base malts require mashing to convert their starches to simpler sugars. If these grains are not mashed, unconverted starches are released into the wort and eventually wind up in your beer. The result is excessive haze and the potential for a "starchy" flavor. Starch can also serve as a potential carbon source for contaminating bacteria or wild yeast strains.
When steeping, the temperature of the water is not critical — we are simply soaking the grains to get the color and flavor compounds out. Recipes typically recommend steeping temperatures between 130 °F (54 °C) and 170 °F (77 °C). Anywhere in this range will work, so don't worry about the precise temperature recommended.
The amount of water used is also not critical. As long as there is enough to completely immerse the grains, it doesn't matter if you use a little more or less than recommended. Steeping in larger amounts of water extracts more of the flavor and color from the grains. However, it can also extract tannins and result in an astringent taste in your beer. If you steep your grains in lots of water and taste some astringency in your beers, cut down on the amount of steeping water.
Alternatively, you can steep in the same volume of water if you adjust the pH of the "grain tea" to below 5.8, but not below 5.2, as you steep. Thicker "grain teas" have a better chance of falling into this pH range without any adjustment.
My normal process for steeping grains is this: Heat 3–4 quarts of water per pound of grain (6.3–8.3 L per kg) to 150 °F (65 °C) in your brewpot. Put the grain in a muslin or nylon bag. Soak the grain in the hot water for 15–45 minutes. Remove the bag and place in a large colander. Rinse the bag with 150–170 ºF (65–77 ºC) brewing water, allowing the runoff to fill the brewpot to the correct amount for boiling. Bring the wort in the kettle to near boiling, add malt extract and proceed boiling.
Cold steeping is a variant of the usual homebrew steeping procedure. In cold steeping, specialty grains are steeped between 40–55 °F (4.4–13 °C) for several hours to overnight. Cold steeping is most often used on dark grains and supposedly results in a less aggressive flavor from these grains. The "grain tea" from a cold steep can be added at any time during the boil, including late in the boil.
Performing a full mash requires equipment beyond that used in normal extract-with-grains brewing. (See "Infusion Mashing" in the March-April 2003 issue for an introduction to full-scale mashing.) However, you can partial mash in your brewpot with just a grain bag.
When you steep grains, the temperature is not that important. In mashing it is critical. A few degrees variation can cause a noticeable difference in the beer. Most mashes rest between 150–158 °F (66–70 °C). (In a single infusion mash, this will be the only rest.) As such, follow the rest temperatures in the recipe exactly, or be sure you understand how to choose your own rest temperatures. Either way, you must carefully control the temperature of the mash.
The volume of water is also more critical when mashing. Recipes typically recommend 1–2 quarts of water per pound of grain (2–4 L per kg). More water results in a mash that converts slower, but produces a more fermentable wort. Less water results in a mash that converts faster but produces less fermentable wort. Again, follow the recipe or be sure you understand the consequences of changes.
When partial mashing, I usually heat 1.5 quarts of water per pound of grain (3.1 L per kg) to about 12 °F
(6.7 °C) above the intended rest temperature. As with steeping, I put the crushed grain in a muslin bag and immerse it in the hot water in my brewpot. Unlike with steeping, I monitor the temperature to keep it within a couple degrees of the target. If it is off, I adjust up or down by adding small amounts of boiling water or cold water. You can also heat your brewpot. To do so, add heat for 15–45 seconds then stir the mash and check its temperature in two or three places.
Let the partial mash rest for 45–60 minutes, then lift the grain bag out and rinse with hot (170 °F/77 °C) water. Use approximately as much water for rinsing the grains as you did for mashing them. (The process of rinsing the grains in a mash is called sparging.)
If your partial mash consists of more than a few pounds of grain per 5-gallon (19-L) batch, it will be worth your while to check the pH. You can do so with pH papers or a pH meter. A cooled sample of your wort should register a pH between 5.2 and 5.6.
If the recipe calls for both grains that require mashing and grains that can be steeped, mix all the grains together in the mash. There's no need to steep some of the grains and mash others separately, although you can if you wish.