Mash Tun is a brew house vessel used for mixing the ground malt (grist) with temperature-controlled water. This is called “mashing”and the porridge-like result is called the “mash.” See mash and mashing. The mash is held at a predetermined temperature and time (e.g., at 65°C for 1 h) until the malt starches convert to sugars, and the dissolved malt sugars (wort) are rinsed into the kettle where hops are added. The mash tun is a single vessel where the mashing and wort runoff take place in the same vessel.
It is predominantly used for brewing ales and other top-fermented beers, particularly in the UK, using a single-temperature infusion mash.