The industrial trick of moistening malt just before milling can allow finer grinds—and thus greater efficiency—without stuck mashes. Here’s how to do it at home.
Published: May 30, 2020
Many things in brewing are a trade-off. For example, you can collect more wort from your grain bed to get more sugars, but then you have to boil longer to evaporate the excess water.
Another familiar trade-off is seen in milling. Generally, the finer the grist, the smaller the pieces of endosperm. Smaller endosperm pieces result in a higher extract efficiency. However, finer grinds also tend to cause problems when lautering because the pieces of husk are too small to form an efficient filter bed. As such, there is an optimal degree of fineness to a grist—fine enough to achieve a reasonable extract efficiency but not so fine that the brewer has trouble lautering.
Malt conditioning, or conditioned milling, is a way to cheat that trade-off. The technique allows the brewer to mill the endosperm of the malt more finely, yet still produce adequately sized pieces of husk for a filter bed.
When malted barley is dried during the malting process, its husk becomes very brittle; when milled, it shatters. The tighter the mill gap, the tinier the husk pieces. However, if the husk is wet, it becomes somewhat leathery and pliable. When run through a mill, the husk will break into only a few pieces. Or, it may pass through the mill split, but still intact. Unfortunately, if the endosperm of the malt is also wet, a roller mill will not crush it. It will simply extrude a starchy mush that fouls the rollers.
So, for conditioned milling to work, the brewer needs to wet the outside of the malt but not the inside.
The key to malt conditioning, then, is to quickly wet the husk, then crush the malt before the endosperm starts absorbing water. Commercially, this is most often done by steaming the malt as it is augured from grain storage to the mill. This works well because every bit of the grist is exposed briefly to steam, quickly penetrating the husk. But because the time of exposure is short—and because the malt is milled immediately after steaming—the moisture has no chance to soak far into the kernel.
Of course, few homebrewers auger their grain into their mills (and for good reasons). There are a couple ways, however, that homebrewers can condition their malt at home.
The simplest way to condition malt at home is to pour it into a bucket (or similar container), spray it with water, and mix it around with your hands. Use a spray bottle that can produce a fine mist. The weight of the water should equal 2 percent of the weight of the malt. If you weigh your malt in kilograms, this is easy to calculate. Because a liter of water weighs 1 kg, simply multiply the weight of the malt by 0.02. That will be how many liters of water you’ll need to spray.
Immediately before milling, spray the malt a few times, mix it with your hands, and repeat until the grist has been treated. Then, mill.
This method has the advantage of being very simple. However, it has the disadvantage that the water will not be evenly dispersed unless you mix well every time you spray the malt. However, the longer you take mixing the malt, the more time the water has to soak into the endosperm. It’s another trade-off. In the worst-case scenario, you’re left with some overly wet grain, which can gum up your mill, and some completely dry grain. The challenge grows greater as the amount of malt increases, although you can partially compensate for this by dividing the entire grist into portions and processing the portions separately.
A slightly more complex approach is to put your grist in a large nylon steaming bag and steam it immediately before milling. To do this, put a lid on your hot liquor tank (HLT) to trap the steam it is giving off. Place the bag in the HLT—above the water line—and close the lid. Steam the malt for 30 seconds. (Seriously, just 30 seconds. Longer is not better.) Then, mill.
This works well, but there’s a trade-off here, too. Steam will quickly and evenly penetrate the husks of the exposed grain. If you expose the grain to the steam for only 30 seconds, you can’t overdo it. However, the grain in the center of the bag will not be conditioned because the grain around it will shield it from the steam. As before, you can get better results by processing smaller amounts of malt at a time. The smaller the amount of grain in the bag, the less grain will be “hidden” from the steam. The other obvious drawback is that you risk dunking the entire bag into water if you’re not careful. Also, if your HLT is nearly full, the amount of malt you can process at one time is limited.
Despite these trade-offs, I prefer this method because—other than dunking the bag in the water or steaming it too long—you can’t really make a mistake. At worst, some of the malt is conditioned and some isn’t. You can’t overly wet any of the kernels.
If you are thinking of trying either method, it will benefit you to conduct a dry run (if you’ll pardon the pun) to fine-tune your crush. First, crush some malt—of a type you use frequently—in your usual manner at your usual mill-gap setting. Crush just enough to get a feeling of the quality of the crush. Then, condition that same amount of malt and crush it. Next, tighten the mill gap slightly, condition another sample of malt, and mill again. Examine the milled samples.
As long as the husk sizes in the conditioned malt are larger or at least as large as in your regular, dry grind, keep narrowing the mill gap and crushing. When you reach a point where the husk sizes are comparable, note the size of the mill gap. (You can measure the gap with a spark-plug gap tool.) Also, look at the range of sizes of endosperm pieces in the conditioned malt vs. your usual grind. If there is a distinct difference, the procedure worked.
Now, here’s the big question: As a homebrewer, should you condition your malt? I would start answering the question by asking whether you are happy with the results you achieve with dry milling. The old adage, “if it ain’t broke, don’t fix it,” may apply. Also, think back to your dry run. Did conditioning the malt allow you to tighten the mill gap significantly and produce a finer crush of the endosperm? If it didn’t make much of a difference—with your favorite malt on your usual mill—then it won’t make much of a difference in your brewery.
However, if the dry run looked promising, give it a shot. It only takes a few minutes to condition your malt. Once conditioned, you don’t need to make any further adjustments to your brew day.
Finally, if you obsess about your extract efficiency, you definitely should try this. It’s a no-brainer. Performed correctly, conditioned milling allows you to crush more finely—and therefore get more extract from your grain—without causing problems during lautering. It’s a way to have your cake and eat it, too.
Photo: Matt Graves/www.mgravesphoto.com