Lauter Tun
A lauter tun is a vessel that is used to hold the mash in lautering. Mash is a mixture of hot water and crushed grain that is used in making malt drinks such as ale.
A lauter tun usually has a false bottom. This means that the bottom has holes that let the sweet wort run through while leaving the grain husks behind. It also has rotating arms that are used to agitate the mash. Usually, the mash is sprinkled or sprayed with hot water as the wort is being drained. This technique is called �sparging.� The grain husks that are left behind after lautering while devoid of sugars are still rich in nutrients and can be used as cattle feed.
Lautering is the process of extracting the sugars from the grains in the form of a liquid which is called wort (rhymes with �hurt�). �Lauter� is German for �to clarify.�
It is very easy and quite cheap to construct a lauter tun from ordinary picnic beverage coolers. Everything you need can be bought at your favorite hardware store. You can choose to use a rectangular chest type cooler or a cylindrical one. The rectangular coolers usually come in 20, 24, 34, and 48-quart sizes. It is up to you to decide how large a batch of ale you intend to brew.
The size of the cooler is important only in relation to the depth of the grainbed. Typically, the grainbed should not be less than 4 inches deep but not more than one and a half feet deep. As a rule, your grainbed depth should not be less than half of the shortest dimension of the tun floor but no longer than twice its longest dimension. If there is too much grain in your mash, you might run into a �stuck sparge� meaning no fluid is draining out from the mash. This is because your grains are too compact. On the other hand, if your mash is too shallow, it may not clear adequately.
The goal in lautering is to drain out all the sugars from the grainbed, and this can be done effectively by ensuring two things. First, that the grainbed is completely saturated with water. Keeping the water level at least one inch above the grainbed helps you avoid a stuck sparge. The second is that the water drains in a slow and uniform fashion. You can do this by using a ball valve or a stopcock in the outflow.
Cylindrical coolers usually have a spigot that can be removed to give way to an outflow tube. In the case of rectangular coolers (which usually have no spigots), it is useful to have vinyl tubing running over the wall of the cooler to siphon out the wort. A clamp should be used to regulate the flow. The ideal draining rate is about one quart per minute.
The false bottom you will use for lautering can be bought ready-made at the hardware store. As an option, you may also want to construct your own manifold system. Everything you need to make your own lauter tun should cost no more than $40.