Mash/Lauter Tun: Projects

Time has a way of revealing flaws in our efforts, mine included. This is true of the RIMS mash tun that was built in the December 2001 issue. I’ve used that prototype for two years and discovered a need for change. Our new version should benefit every home brewer contemplating the switch to all grain brewing.

English brewers and most US microbrewers use what is called a “single infusion mash.” In practice, a heap of skillfully malted barley is crushed, placed into the mash tun and warm water is stirred in. After a brief wait while natural enzymes convert starches to simple sugars, the miracle is complete and you have wort! Next, the mashed barley malt heads for a lauter tun to separate liquid from solids and the resulting wort goes into the boil kettle. This wort is boiled, hops are added and you know the rest of
the story.

Many smaller micro-breweries operating on a limited budget use a combined mash/lauter vessel to save space and equipment costs. Once the basic mash/lauter tun is built you may decide your needs don’t include anything more. For those who want greater control over the brewing processes, we’ll describe ways of adding a different filtering method (called a false bottom) and a way to add heat to your mash tun.

Project One: The mash/lauter tun

Insulated coolers make ideal mash tuns. They are inexpensive and made from food-safe plastics. To convert a cooler to a mash tun you need a way for the wort to be removed, leaving solids behind. If you have never mashed, milled grain includes large particles, flour-sized bits and various sizes.

Step One: Coolers come equipped with a drain hole. Unscrew the original self-closing tap. This leaves a 1/2” hole ready to accept a bulkhead fitting.

Step Two: Make a bulkhead fitting from a close nipple (1/2” x 1/2”), two O-rings, 1/2” ball valve, and 1/2” x 1/2” compression fitting. This will create a leak resistant pathway from inside the cooler to outside.

Step Three: Cover threads at each end of the close nipple with 2–3 wraps of Teflon tape (or food safe pipe dope) and screw everything together a bit more than finger tight. You may have to make a plastic washer to add enough thickness to create a seal. Over tightening will compress the O-rings too tightly and damage them.

Making a filter is simple (most brewing texts refer to a device called a manifold made of slotted pipes. Our filtration device replaces this.) It requires copper tubing (3/8” in our example) extending from the 1/2” x 1/2” compression fitting that leads downward to a length of stainless steel flexible tubing below. Wondering how the tube is 3/8” and the compression fitting is 1/2”? Me too. I’ll guess that tube is measured by I.D. or inside diameter, the compression fitting by O.D. or — you guessed it — outside diameter.

Step Four: Cut the original fittings from a 12-24” x 1/2” length of stainless steel flex covered water supply line — longer is better. Be sure you purchase 1/2” tubing or it will be difficult to expand to wrap over a 3/8” T fitting.

Step Five: Cut a 4-6” (100-150 mm) length of 3/8”copper tube and solder on a 3/8” T fitting. Be sure the flux and solder are rated for food use and do not contain lead. Using a tubing bender, gently curve the copper tube to the bottom of your cooler/tun. Using stainless steel ring or clamp fittings, copper or stainless steel wire (ordinary “stainless” hose clamps contain iron parts, which are very bad for beer) secure the mesh tube over the open ends of the T. Insert the tube into the compression fitting and tighten.

That’s it. You have a functional mash tun. It is ready to use after you thoroughly clean anything that has been handled or soldered. Use a strong cleaner like TSP or PBW to remove all traces of oil and soldering flux.

If you find that you get bits of grain in the runoff — I haven’t — a circle of copper window screen or several stainless steel scrub pads laid atop the flex should help create a dense and free-flowing compacted-grain filter bed even quicker. If you like this filter for your mash tun, it works wonderfully in a boil kettle.

Project Two: Adding a false bottom

If you are familiar with lauter tun descriptions, most mention a false bottom. The false bottom — whether a layer of spruce needles used in ancient brewing, or the slotted stainless steel sheet used at your local microbrewery — supports the grain bed, which serves to filter the wort.

In the mash tun (or mash/lauter tun) crushed grains are added to warm water. The result is thin barley porridge. If you were to drain the thin part, the desirable wort, it would include chunks of grain. Fortunately, this porridge will act as its own filter as it compacts and compresses.

Recirculation is a process of draining freshly produced wort from the mash tun. It will initially contain many tiny particles. Collected wort is added back to the mash tun and drains through an increasingly compacted layer of grains. The false bottom encourages the formation of a thick bed of large grain particles — a natural filter.

Most experts suggest that a smaller grain particle is easier to convert into wort. However, you may have to adjust the crush of your grain mill to a coarser grind, or risk a stuck mash. That’s what happened to me on my first use of the new mash tun with stainless steel false bottom. A coarser setting on my grain mill solved
the problem.

The cooler I purchased is 10.25” in diameter at the top and tapers to less than 10”. The false bottom is 10”, perfect for kettles and mash tuns made from 15-gallon stainless steel kegs. You must cut the screen to fit.

Step One: Cut a cardboard circle 10” in diameter.

Step Two: Measure upwards from the bottom of the mash tun 2–21/4”. This depth allows for insertion of a heating element in project three. If you are doing all of this in one project, read all of project three before proceeding.

Step Three: Fit the circle into the mash tun and adjust the size until your cardboard template precisely reaches the depth mark. It is very easy to cut undersized and the fit must be tight; the mash tun will expand as it heats. Then cut the stainless steel false bottom to size.

Step Four: Though your false bottom is friction fit to the mash tun, heat will expand the vessel by 1–3 mm in diameter. The false bottom could tilt or fall. You need a support device built of bent brass or CPVC pipe. I’ve used both and prefer the bent and welded brass.

Project Three: Adding heat — RIMS

The third addition to the basic mash tun provides an internal heat source to the mash tun.

There are two common methods of adding heat to your mash tun. The RIMS (recirculating infusion mash system) has become a standard in home brewing. The HERMS or Heat Exchange Recirculating Mash systems are gaining popularity.

HERMS systems recirculate liquid between two vessels, a hot liquor tank and the mash tun. A coil of metal tubing is placed into one (or both) vessels and heated liquid is pumped through the coil. This moves heat to the cooler vessel. HERMS has some attractive features. Maybe we’ll build one next year.

Traditional RIMS systems place the heat source outside the mash tun. Our system puts the heating element into the mash/lauter tun and moves liquid (wort) past the heat source.

Systems similar to ours are very common in the UK, where the mash tun, lauter tun, and boiler are all one vessel (don’t try boiling in a cooler, the plastic is not as heat resistant as the British polyethylene tubs.)

Several styles of heating elements are available. You can use elements like those in British BruHeat, Electrim and similar systems, or purchase Chromalox water heater elements. Every element is designed to run on 220/240 Volt current; driving them with US voltages, 120V, results in less heat
output, which is preferable. The less heat produced per inch means less opportunity to scorch your precious wort. Double or quadruple folded elements are best as burnt wort is not palatable.

We used a doubly folded element that fits the diameter of our mash tun. It’s a Chromalox SGW 2207 (2000 Watts) and is made of nickel alloy. It produces 500 Watts of heat.

Any heating element requires control. UK homebrewers have access to the previously mentioned systems that include a controller. We Colonials must use one of their systems, or build our own controller. You could make a simple controller (Build a simple RIMS: Projects (BYO Dec, 2001) but why not use a sophisticated controller? See “Lager Climate Control” in May–June 2004 BYO. The Ranco ETC 111,000-based controller will be equally happy controlling a heating element as a heating pad! Stay within its capabilities: 120VAC, 16A, or 208/240VAC, 8A.

Interior RIMS-style Heating

Step One: Drill a hole in your cooler. Measure the interior depth and mark the exterior to reflect the interior bottom. Depending on the heating element used (1”–1 1/2” diameter or 25–37 mm), measure up at approximately 1/2” above the center of the hole to allow for the curvature of the interior bottom.

Step Two: Drill (or cut) through the exterior wall of the cooler with an appropriate sized hole saw (large enough for a 1–2” PVC protective plastic cap.)

Step Three: Remove the foam insulation carefully and then cut a smaller hole (using a 1”–1 1 2” hole saw) for the heating element.

Step Four: Place an appropriate-sized O-ring around the threads of your heating element, insert through the cooler wall, and secure with a brass or stainless steel hex nut of matching size. (Water heater elements will have the nut on the inside of the mash tun, and a securing nut will be on the outside.)

Step Five: Drill a hole through a PVC cap and insert a power cord. Wire the cord to the heater element and be sure to include a ground connection. Push the cap into the large hole after you have completed leak testing. An installation using a BruHeat controller will require a larger exterior opening to accommodate the controller box.

Project Four: Building A Thermowell

To best control either heating element, we need to place the controller’s heat sensor inside the mash tun. It’s not waterproof so we need a device called a thermowell. It is a closed-end copper tube inserted into the mash tun. If you have access to stainless steel tube, it’s even better.

The thermowell could be loosely placed into the mash, but vigorous stirring would dislodge it. We need a method of holding the tube upright. You might devise a more clever restraint device; I used semi-circles of flattened copper tube, soldered to the upright thermowell.

Step One: Measure from the top of the mash tun to your false bottom. Cut a length of copper tube to similar length. Solder a cap to one end, forming a waterproof thermowell tube.

Step Two: Cut two lengths of copper pipe that are larger than half the circumference of your cooler, approximately 17” or 432 mm. Flatten the tube and solder each hoop to the upright. One should be near the bottom, the other near the top.

Step Three: Thread a 90° L onto the thermistor, then dry fit to the thermowell. Your temperature probe may not pass through the right angle. If so, use a 45° fitting or just ignore it. The purpose is to prevent the thermowell from filling with liquid or debris.

The Final Piece — A pump

The recirculating mash system is driven by a pump. A wort pump must be capable of moving boiling hot liquid against the force of gravity and resist injury from grains. Your local homebrew shop can advise you in the purchase of a new pump and how to use it.