Imagine a 10-foot laurel hedge, fairly open and loose. Not carefully groomed. Then imagine a steady, soft breeze blowing a pallet of Styrofoam peanuts through it.
If the breeze changes or stops, a lot of the peanuts fall. If the wind suddenly gusts strongly, the peanuts go right through the hedge. If somebody drives a car through the hedge, a lot of the peanuts go through the big hole.
Well, when a brewer seeks to separate sweet wort (Styrofoam peanuts) from the husks in the mash, he’s creating a dynamic that is really not too different from Styrofoam peanuts and a laurel hedge. A lauter is a matter of balance — or in fact several different balances balanced together. But in essence it is using milled grain from the mash to act as a filter (laurel hedge) for itself.
Lautering, the act of drawing the sweet wort from the oatmeal-like mash after enzyme action has slowed, is simple enough. Like any finesse operation, it gets easier with practice and benefits well from systematic measuring, tweaking, and trial and error.
The grain begins suspended in liquid, the mash water that has by now become sweet wort. The grain is a bit too heavy to float, but the liquid helps support it and keeps it from compacting into a mass that is too dense to allow liquid to flow through it. But watch it: Too much liquid isn’t good because if the grain mass is too loose, it won’t filter well. Also, the slow flow of liquid through the grain is what keeps the filter bed established. Lauter too fast and extract is left behind. Stop the flow and risk the filter bed coming apart. It’s the flow itself that keeps the irregular-shaped chunks together and keeps them acting as a self-filter.
Standard Operating Procedure:
So you milled your malt, not to fine because that would cause a stuck mash and not too coarse, because that would reduce your extract. You mixed it with water in a mash vessel, and you held it at one or more temperatures for a measured time period. You added rice hulls (basically, pure husk) if you had a lot of wheat in the mash, because wheat is shy of husk and is known to compact and not flow. Now you have a goopy sweet mass, kind of like really healthy, grainy oatmeal that smells a lot better than oatmeal. You want to get the liquid part out and into your brew kettle, leaving the husks — “spent grain” — behind for breadmaking or garden mulch.
The routine is to place the mash into a vessel with a false bottom, meaning that some small distance above the bottom of the vessel is a tight-fitting screen or perforated plate. At the lowest level is a drain hole with some kind of flow-regulating device; up top is a way to gently add water. Sometimes, the mash tun (or vessel) itself is set up as the lauter tun, meaning that there is no transfer from one vessel to another.
Here’s how it works. The liquidy mash settles somewhat, and the valve at the bottom is opened very slowly. A gradual migration of the liquid toward the valve begins. At this point the liquid is cloudy and completely full of husk chunks, haze, grasshopper legs, stems, and so forth. But as the liquid moves through the mash, the little moving chunks get hung up in the matrix of grain husks. As the liquid drains out of the valve, the grain is pulled by the liquid flow to the vessel bottom and begins to work as a filter. When the grain was suspended in water, the liquid flowed more easily.
You want to extract as much wort sugar from the spent grains as possible, so gently sprinkle water — heated to a point that will keep
sugars soluble, about 158° to 172° F — on top of the grain bed, at a rate that closely matches the outflow to create equilibrium of the water level. As you add pure water at the top, it moves through the mash, picking up sugars and flavor. The water maintains the filter bed and gets every last drop of goodness out of the grain. Don’t let your sparge water get hotter than 172° F, because it will make soluble some nasty tannic flavor components in the grain husks and your beer will taste astringent later.
It’s critical to pour the sparge water gently on top of the grain. Pouring a stream into the grain will dig a hole, disrupt the filter matrix, and cause more of the water to run straight through the hole, bypassing too much of the grain and leaving too many desirable solubles behind. Professionals and some serious homebrewers have rotating arms or gentle spray patterns to just dribble the sparge water on. Even the most cavalier masher should gently place a saucer on the grain bed and direct the sparge-water stream onto the saucer. This prevents the stream from digging a deep hole.
The first run-off looks cloudy and contains visible chunks of husk, so clever brewers recirculate (a common pro brewers’ term for this is the German word for whirlpool, vorlauf). They gently pump the first runnings back to the top of the mash vessel, where it must pass through the grain matrix again. Less slick but equally clever homebrewers use two pitchers, letting one fill as they gently pour the other back onto the saucer at the top of the mash tun. After 15 percent to 25 percent of the mash volume has been recirculated, the run-off will begin to look noticeably clear.
Remember that a mash is susceptible to hot-side aeration — atmospheric oxygen bonding to the non-water portion of the mash — and that this may lead to off-flavors developing later in the beer. As you mix the mash in the vessel, and especially if you transfer from a mash vessel to a separate lauter vessel, do it gently and smoothly, mixing in as little air as possible.
Tools of the Trade:
Mash vessels are sometimes insulated, so a single temperature can be maintained for a long period without the addition of heat. Many homebrewers use a picnic cooler or ice chest for mashing. Even outdoors in cool weather, a mash consisting of 10 pounds of grain and the corresponding three gallons or 3.25 gallons of water will hold within five degrees over a 90-minute mash, as long as the cooler insulation is decent. Other brewers mash in a metal kettle or converted steel keg, which offer brewers the advantage of being able to apply heat for multi-temperature mashes.
You can easily build a false-bottomed lautering vessel. There are many ways to do this, ranging from simple to as fancy as you want. The easiest and probably least costly is to drill hundreds of 3/16-inch holes in the bottom of one five- to seven-gallon food-grade polyurethane bucket, then nest that inside a second polyurethane bucket that has one hole in the side just above the base. The drain hose comes out of that hole, and the inline regulating clamp fits in here outside the bucket. Sometimes brewers wrap the device in insulating foam to help keep the mash from cooling too much.
To use this “Zapap” lauter tun (named by early proponent Charlie Papazian), start by adding “foundation water” with the valve closed. This is mash-temperature water (around 160° F) that fills the space below the false bottom. Then, gently ladle the mash into the vessel and open the valve on the hose (open it just a bit for a slow flow!) while directing the flow into one of your recirculation pitchers. The runnings will be hot, so don’t use a non-tempered glass pitcher that could crack when it touches hot liquid.
There are variations on vessels and false bottoms: Listermann Mfg. makes the Phil’s Phalse Bottom, an arched plastic false bottom with sizes designed to fit standard polyurethane buckets, five-gallon insulated water coolers, and 10-gallon water coolers. They work well and require less foundation water than a double-bucket lauter because the space under the false bottom is much smaller.
Brewers who mash in a rectangular cooler sometimes make a trident shape out of copper or plastic tubing (regular PVC is not rated for temperatures that occur in mashing; use the high-temperature-rated CPVC), then cut dozens of grooves in the arms with a hacksaw. The “handle” of the “trident” is plumbed through the drain hole in the cooler, and the wort flows out there. Copper “theta” shapes or circles are often built by brewers who mash in a metal kettle or converted keg. See “Build This Mash Tun for Under $50,” page 38, for a mash/lauter tun that uses pizza screens as the false bottom.
A simple enhancement to your lauter system is a sparge sprinkler, a step up from a saucer on the grain bed. Easiest is probably a yogurt container suspended over the grain bed by a stick through the rim. If you punch dozens of small holes in the container, a pitcherful of sparge water poured in there will dribble out slowly without disrupting the grain bed. You can also spiral a piece of copper tubing and punch regularly spaced holes in it, then run sparge water right out of a separate sparge-water vessel (usually called the HLT, for hot liquor tank).
When you first start to sparge, examine the output that is slowly filling your pitcher. It should have deep color and a sweet taste. You also should note haze as well as little chunks of husk suspended in there. After your first pitcher is more than half full, switch the hose to the
second pitcher and gently pour the run-off back onto the saucer that sits on top of your grain bed. (Remember, avoid aeration as much as possible at this point.) The liquid will join the slow downward flow through the matrix of husks, leaving chunks and eventually haze behind. When the run-off looks clear and bright, direct the outflow into your brew kettle.
As your wort comes out and sparge water goes in, resist the urge to open the valve wider to speed things up. The quest for speed can lead to a stuck mash — where the flow stops because the grain bed got too compact — and it will lead to reduced extract, meaning that some sugar was left behind in the grain husks. Expect your run-off to take more than half an hour for a five-gallon batch, and continue to run off until you have achieved your desired pre-boil volume. Take a gravity reading of your final runnings. (Careful advanced brewers constantly monitor the run-off gravity and stop when it gets too low, desired volume or not.) Take a reading of your wort before you boil, remembering that the boil will concentrate it and raise the gravity. Make notes about the process and how much you recirculated. Drink your hydrometer samples.
At some point, many brewers feel that they are bonding with their grain bed, but remember: Don’t climb into the grain bed. That would certainly disrupt the filter matrix.