Mashing Variables
In this article, I’ll discuss the refinements you can make once you’ve got your first few mashes under your belt. I’ll describe the variables that have the biggest impact on your finished beer and also touch on some of the practical aspects of being an all-grain brewer.
Buying and storing grain
One benefit of all-grain brewing is that your per-batch cost is lower than in extract brewing. (Of course, this is partially offset by the one-time cost of new equipment.) You can save even more money if you buy some of your grains by the sack. A sack of grain usually weighs either 50 or 55 lbs. (23 or 25 kg) and your cost per pound is less than a buck. Many all-grain homebrewers buy a sack of base grains, then buy the specialty grains for each batch as they go. Keep in mind, though, that malt is a food product and does go stale over time.
Also remember that rodents and insect pests would love to get into your grain, and they will if you don’t store it properly. Many homebrewers buy a 55-gallon (208 L) plastic garbage can with a sealable lid to store their grains in. This will keep pests out and — if located in a cool, dry place — your (uncrushed) grains should keep for about a year.
The crush
One thing you can do that greatly affects your brewing is to get a good crush. The degree your malt is crushed affects many aspects of your mash, and the wort you yield from it.
The fineness of a crush varies from the grain kernels barely being disturbed to the grain kernels being ground into a uniformly fine powder. The optimal crush, as you no doubt suspect, lies between these two extremes. The finer you crush, the higher your extract yield. However, with finer crushes, it is harder to collect your wort as the grain husks are too small to act as an efficient filter. In addition, the more pieces the grain husks are broken up into, the more tannins and other unwanted husk components will end up in your wort. Ideally, you want to crush finely enough that you get a good extraction efficiency, but coarsely enough that you can lauter with ease and minimize off flavors and astringency. So how do you do that?
The biggest variable affecting your crush is your mill gap — the space between the rollers in your grain mill. It would be nice if there was an optimal mill gap, but the best gap size depends on the grains you are milling and — to a lesser extent — the speed at which the rollers on your mill rotate. In general, however, a mill gap between 0.035 and 0.050 inches (0.89 and 1.3 mm) is thought to be a good, all-purpose setting for barley malt.
A second variable affecting your crush is the speed that the rollers rotate. The rollers on hand cranked mills rotate much slower than the rollers of commercial mills. (Their average speed is 400 RPM, for the optimal 9.8 inch (250 mm) diameter rollers). As such, hand cranked mills crush more coarsely when set to the same gap size. In contrast, home malt mills powered by a portable drill greatly exceed the proper speed and may crush too finely. To get the proper grain mill speed, you need to get a motor and control the speed with “pulleys,” more properly called sheaves. (See the October 2003 issue of BYO for more.)
Most homebrew malt mills are suboptimal in one or more respects when compared to full-size commercial mills. Most are either hand cranked or drill powered (i.e. rolling too slowly or too quickly). The diameter of the rollers on homebrew mills is frequently smaller than on commercial mills. And, many mills have a fixed gap, so the mill cannot be adjusted for different grains. Still, most all-grain homebrewers manage to get crushes that yield extract efficiencies in the same ballpark as most brewpubs or microbreweries. How is this?
You can judge the quality of your crush by examining the grain discharged from the mill or by brewing with it. What you want to see is few or no uncrushed kernels, plenty of kernels broken into two to four pieces and a minimal amount of flour. If you think your grain looks like it is crushed too finely — or you get high efficiencies, but stuck mashes and astringent beers — you have a couple options. You can switch to a larger gap setting, if your mill is adjustable, or start hand cranking, if you were using a drill to power your mill.
Conversely, if your grain looks undercrushed — or you get low efficiencies, but have no problems lautering (even when you run the wort off quickly) — you can set a smaller gap or motorize your mill.
In the case of undercrushed malt, you can also mill the grain twice. Even if you have a non-adjustable, hand-cranked mill, a second run through the mill will break up the kernels a bit further. Of course, the second crush can be a bit of a pain, as the grain won’t flow as easily in the hopper as it did when it was whole. So, the second crush may take considerably longer than the first. But, it can be worth it if you are brewing a big beer (and need all the extract efficiency you can get) or if your efficiency is very low.
The point is, although we homebrewers typically use mills that commercial brewers would deem sub-standard, there are workarounds we can use to get a decent crush. These operations would be impractical for commercial brewers who crush much larger amounts of grains and, for economic reasons, need to do so quickly (thus ruling out hand cranking or milling the grain twice). But, when milling less than 20 lbs. (9.1 kg) on Saturday morning, it’s usually not that much of a hassle.
Temperature differences
Everyone knows that temperature is important in mashing. However, one temperature-related aspect of mashing is usually left for the homebrewer to figure out on his own — temperature consistency and stability.
It’s fairly easy to end up with temperature differences in your mash. Variables that increase the potential for temperature differences include: direct heating of the mash, thicker mashes, less stirring of the mash, large initial temperature differences between your grains and strike water and large temperature differences between your target mash temperature and your mash tun.
If you have a mash tun that you can heat, be sure to stir well when doing so. You may even want to stir for a minute or so after you turn off your burner as heat can continue to flow into the mash through the metal near the burner.
Most homebrewers mash fairly thickly, with mash thicknesses around 1.25 quarts of water per pound of grain (2.6 L/kg or a 2.6:1 ratio) being popular. However, if you are going to be heating the mash, you may want to go with a bit thinner mash. For example, if you were doing a heated step mash, a mash with a thickness around 1.9 qts./lb. (4 L/kg, or 4:1) would be easier to even out than a thicker mash. (This is because water conducts heat better than grain solids.)
When mashing in, your crushed grains are going to be much cooler than your strike water. Ideally, mixing the two should yield a mash right at your target temperature. For grains stored at around room temperature, heating your brewing liquor 10–11 °F (5.5–6 °C) over your target temperature will get you in the right range (assuming a roughly average mash thickness). Some software packages will calculate your ideal strike water temperature based on temperature and weight of your grain and target mash thickness. You can also determine the correct temperature by trial and error. Note your strike water temperature and initial mash temperature for two or three brewing sessions and you’ll quickly get a good feel for what your strike water temperature needs to be. The closer your strike water is to the correct temperature, the quicker your mash in will be. Also, a little stirring should quickly even out any temperature differences in the mash.
The temperature of your newly mixed mash can potentially be affected by the temperature of your mash tun. Ideally, you want to heat the mash tun to right around your target mash temperature prior to mashing in. Filling your mash tun with brewing liquor heated to a few degrees above your target mash temperature should do the trick. Let the water sit for a couple minutes, then return it to your hot liquor tank to be used later as sparge water. If you mash in a non-heated mash tun, the sides of your mash will quickly become cooler than the middle of your mash.
Temperature stability
Once you are mashed in, your grain bed will start losing heat. The better insulated your mash tun is, the less heat loss you’ll suffer. Temperature losses will be greatest near the edges of your vessel. You can insulate your mash tun simply, for example with towels, with a fitted “jacket” that goes over the vessel or by wrapping it in fiberglass insulation. Even if your mash vessel is fairly well insulated to begin with — for example, if you mash in a converted picnic cooler — adding a little extra insulation will help you retain more heat.
So essentially, differences in mash temperature may exist initially within the mash and can form during mashing due to heating or cooling. In all cases, stirring thoroughly will even out the mash temperatures.
However, as you need to open your mash tun to stir, you’ll also lose heat each time you do. As such, you’ll want to add some heat each time you stir. If you are mashing in your kettle (or have a heatable mash tun), just heat the mash as you stir. If you can’t apply direct heat, you’ll have to add near-boiling water. In the latter case, you should only open the mash vessel and stir if you suspect significant temperature differences exist. The only way you’ll have any idea if this the case is to take good notes the first few times you mash. Take the temperature at several places once you are mashed in. Stir until the temperature differences even out and seal the mash tun. After 15 minutes, open up your mash vessel and take the temperature near the middle and near the edges, then add some boiling water and stir to bring the temperature back to your original target. If the temperature changed little and showed little differences from the middle to the edge over 15 minutes, next time let the mash rest longer before opening it up. If you’re losing significant heat in under 15 minutes, you’ll definitely want to insulate your mash vessel to a greater degree.
On a 5-gallon (19 L) scale, I try to keep my mash within 3 °F (1.5 °C) of my target temperature and keep temperature differences under 2 °F (~1 °C). I mash in my kettle and have a fitted “sleeve” I throw over it for insulation. To keep within my 3 °F (1.5 °C) target, I need to open up, heat and stir every 20 minutes. You’ll have to decide for yourself what amount of temperature deviance you are willing to put up with. The tighter the control you seek, the more you are going to have to monitor, stir and heat your mash. Also, if you are adding hot water to keep your temperature up, you may end up thinning the mash too much or running out of room in your mash vessel.
Wort collection
Once the mash is over, the mash out has taken place and the wort is recirculated, wort collection begins. One factor that greatly affects the quality of your beer is how much wort you collect. The first bit of wort you run into your kettle is high in gravity (up to SG 1.100, depending on your mash thickness) and contains no undesirable elements extracted from the husks. As you continue to run off wort and rinse the grain bed with hot water (sparge), the gravity of the runnings drops and, at some point, the extraction of unwanted husk materials begins. Thus, for every unit of grain you mash, there is a volume of wort you can collect that yields the maximum amount of extract before wort quality suffers.
To find your proper volume of wort to collect per weight of grains mashed, you need either a hydrometer or a pH meter. Measure the specific gravity or pH of the runnings as you collect the wort. When the specific gravity drops to 1.010 or the pH rises to 5.8, stop collecting wort and make note of the volume of wort in your kettle. Divide this volume by the amount of grains you mashed. For example, let’s say you mashed 12 lbs. (5.4 kg) of grains and collected 6.5 gallons (25 L) of wort before stopping. This means that you collected 0.54 gallons of wort per pound of grain (4.5 L/kg). Finding this ratio on your system will allow you to plan ahead of time how much wort to collect from any grain bill by multiplying the weight of your grains by this number. From this, you can figure if you’ll need to add water to your wort, based on your expected boil time. This may be necessary when brewing low-gravity beers from small grain bills. On the other hand, with strong beers — brewed from correspondingly large grain bills — you can use this calculation to predict how long you will need to boil to reduce your wort volume.
