Mashing

Germinated and dried malt can only be stored for a limited time. Its shelf life depends heavily on the time of year and the respective humidity. In dry summer months, malt remains stable for much longer than in a cold, damp Scottish winter. Although it is considered "dry", it still contains residual moisture and the cracked grain provides ideal conditions for mould. Although the malt silos in a distillery are largely sealed airtight, malt can only be stored for around 4 to 12 weeks, depending on the humidity of the environment. Regardless of whether a distillery produces its own malt or purchases it from a large malting plant, the silos are filled using scraper conveyors, modern screw conveyors or blower systems. Each silo is filled from the top and emptied from the bottom - gravity supports a gentle material flow and prevents overlapping. The only decisive factor is to adhere to the sequence of the individual silos when filling and emptying so that no malt remains outside its optimum storage period.

Before the malt enters the mill, it passes through a mechanical sieving machine. It is amazing how many small stones the combine harvester does not remove - the sieving machine ensures that the malt can be processed cleanly and free of foreign bodies. It works with vibrations and gravity.

After cleaning in the sieving machine, the malt is ground. Grain mills are used for this, which are surprisingly similar in design and function to the classic domestic mills. The red colour is also reminiscent of traditional German mills - there has obviously been a standardisation of construction here for centuries.

Different types of mills are used in whisky production:

• Hammer mills: Mostly used for corn, wheat or rye. Rectangular, hardened steel plates rotate at high speed around an axis. The hammers throw the grain against the plates, crushing it.
  
• Roller mills: Standard for malted barley. The grain is pressed between stacked pairs of rollers and crushed by pressure. The rollers can run at different speeds to generate thrust without heating the grain or losing moisture. Well-known models include the Porteus Mill (Craigellachie) and the Bobby Mill (Ardbeg).

The roller mills are set with larger gaps for grinding the malt. The aim is not fine flour, but a coarse grist:
Fine enough to break the grain completely Coarse enough so that the subsequent sieves and equipment do not stick together
The resulting grist contains mainly starch. The enzymes formed during the malting process, in particular amylase, begin to break down the starch into various sugars during mashing. This creates the basis for subsequent fermentation.

The mash tun is used to convert the starch contained in the malt into sugar, which is then dissolved out with water. In the early days of whisky production in the 18th century, the mash tuns were filled with grist and boiling water was poured over them. Stirring was still done manually with shovels to speed up the sugar splitting process.
Originally, the mash tuns were made of wood, similar to fermenters. However, the hot water and constant stirring caused the vats to wear out quickly. With mechanisation, the mash tuns were later made from cast iron segments that were bolted together at the edges. A mechanical, centralised agitator made stirring much easier, increased efficiency and reduced sugar loss in the husks of the grain.
For an optimal sugar solution, the mash must be stirred continuously for several minutes. In the past, the evaporation of large quantities of water during stirring led to a drop in temperature in the mash tun, which made the dissolving process more difficult. It was only in the last century that almost all mash tuns were fitted with a lid made of sheet metal or copper to minimise energy loss and increase the efficiency of the process.

The now more effective form of mash tun is the Lauter Tun!
Modern Lauter Tuns are designed for speed and efficiency: their low height and the sieves at the bottom allow the sugar water to be drained into the underback much faster than with traditional, high mash tuns.
In older systems, a resting phase must be observed after stirring so that the husks float on the sugar water. Only then can the clarified Wort be slowly pumped out. Modern Lauter Tuns not only improve the speed, but also the yield: large, rotating arms with knives mix the grist effectively with hot water and thus dissolve more sugar.

The shape of the base also plays an important role: a curved base makes it easier to dispose of the non-soluble grain residue after the final filling. These design improvements make the separation of liquid and solids more efficient and optimise the quality of the extracted word.

After mashing, the solid residue of the malt remains, which the Scots call draff. These husks contain plenty of protein, minerals and trace elements and are ideal as concentrated feed in animal husbandry. However, due to its high water content, draff is difficult and costly to transport. This is why water is extracted from it in large evaporation plants. One example is the town of Rothes, which operates a central evaporation plant for all local distilleries.
Some distilleries, such as Glenfarclas or Mannochmore/Glenlossie, have their own evaporation plants. This allows the draff to be delivered directly to neighbouring farmers in sacks. This co-operation between distilleries and farmers has a long tradition and was documented by Alfred Barnard for 35 Scottish distilleries as early as 1887.
After the sugar has been dissolved out of the malt, the extracted Wort goes into the wash backs where fermentation begins. The alcohol is then distilled from the resulting "beer". You can find out more about the conversion of sugar into alcohol in the article on distilling.