Whisky Words: Mash Tun

A mash tun is a cylindrical vessel, usually made of stainless steel, used during the whisky-making process to mix the grist (ground grain) with hot water. This step, known as mashing, extracts the fermentable starches from the grain, producing a sweet liquid called wort.

The hot water activates the enzymes in the malted barley, breaking down the starches into fermentable sugars. The process involves adding water to the grain two or three times at increasing temperatures to extract as much sugar as possible. After mashing, the remaining solids are removed and are often used as animal feed or biofuel.

The design of the mash tun is a crucial part of the initial flavor development of whisky.

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In some distilleries, mash tuns are open and made of cast iron or copper; some are them are over a century old and are still in use.

Bottom line: The mash tun is the container in which the mashing takes place. The grist is washed with hot water to obtain a fermentable wort.