Mash Tun Fun

An Intro to Making a Mash Tun

In beer brewing, mashing is the process of combining a mix of milled/crushed grain (typically malted barley with supplementary grains such as corn or wheat), known as the "grain bill", and hot water, known as "liquor".

Mashing allows the enzymes in the malt to break down the starch in the grain into sugars, typically maltose, to create malt liquid called wort.

There are two main methods - decoction mashing, in which a proportion of the grains are heated and then returned to the mash and the temperature then raised; and infusion mashing, in which the grains are heated in one vessel. Infusion mashing is perhaps the easiest method, and that's what this article is all about.

Mashing takes place in a mash tun - an insulated brewing vessel. The end product of mashing is called a "mash".

Making Your Own Mash Tun

The following is a basic guide to making your own mash tun using an ordinary chilly bin.

There are many variations of this design, but this method is a simple way you can make a mash tun using ordinary household items you can find at any decent hardware or plumbing store. 

If you are using a smaller (or larger) chilly bin you can adapt this advice to suit your own equipment and available supplies.

To build this mash tun you will need:

  • A 55-litre chilly bin or thereabouts
  • 16-guage galvanized wire
  • Two 15mm conduit lock nuts
  • Two stainless-steel non corrosive hose clamps
  • Approximately 1-metre of 20mm stainless-steel washing machine (dishwasher) mesh hose
  • Three 15-mm barb to 15mm MP adaptors
  • One 15-mm brass nipple
  • One 15mm brass pipe tee
  • Teflon plumbing tape
  • 15-mm ball valve

A 55-litre chilly bin mash tun will typically be used to brew around 23 litres of beer.

  1. Start by removing the spout that comes with the bin. It should be easy enough to unscrew but you may need to use pliers.
  2. Save the vinyl sealing washer and place about half way down the brass nipple.
  3. Screw on the conduit lock nut to the inside half which helps fasten it to the cooler.
  4. Place in the hole at the bottom of your bin and attach the other lock nut to the outside.
  5. Spin some plumbing tape around the threading of the brass nipple so you have a nice tight seal when you screw on the tee piece.
  6. Screw in the 15mm brass tee.
  7. Use a 20mm stainless steel mesh connecter tube used for washing machines and dishwashers. You may need to get this from a specialist plumbing supplier as most hardware stores stock 15mm steel mesh tubing. Alternatively you can simply flare out the ends of 15mm tubing.
  8. Cut off the ends of the mesh connector tube with metal sheers and remove the vinyl tubing from inside. Once you have the ends cut off, don’t pull the tube, just push the metal down.
  9. After you have the tubing removed from your steel mesh connector you’ll have a lot of stray ends. It is easier to bend these pieces in now so they don’t stab your fingers later.
  10. Once your mesh connector ends are folded in, place your stainless steel non-corrosive hose clamps on.
  11. Next, take your 16-gauge galvanized steel wire and wrap it around a pencil or piece of dowel to create a long spring you can insert into the mesh tubing.
  12. Feed the spring you made into the hose. This will help prevent the weight of the mash and water from crushing the stainless tubing.
  13. Place the stainless mesh hose connector with the spring inside in the bottom of the bin and gently shape the hose.
  14. Wrap tape around the rest of your connectors and slide up clamps but don’t tighten them yet. You want to screw in the connectors before you start clamping so you don’t twist the stainless mesh tubing.
  15. Tighten connectors and hose clamps.
  16. Attach the ball valve and barbed hose adaptor.
  17. Once everything is put together, fill the bin with water to check it is water tight. Test your ball valve by draining the water.

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