Malting is the process of converting barley or other cereal grains into malt, for use in brewing, distilling, or in foods and takes place in a maltings, sometimes called a malthouse, or a malting floor. The malting process starts with drying the grains to a moisture content below 14%, and then storing for around six weeks to overcome seed dormancy. When ready, the grain is immersed or steeped in water two or three times over two or three days to allow the grain to absorb moisture and to start to sprout. When the grain has a moisture content of around 46%, it is transferred to the malting or germination floor, where it is constantly turned over for around five days while it is air-dried. The grain at this point is called “green malt”. The green malt is then kiln-dried to the desired colour and specification. Malts range in colour from very pale through crystal and amber to chocolate or black malts.
The sprouted barley is kiln-dried by spreading it on a perforated wooden floor. Smoke, coming from an oasting fireplace (via smoke channels) is then used to heat the wooden floor and the sprouted grains. The temperature is usually around 55 °C (131 °F). A typical floor maltings is a long, single-storey building with a floor that slopes slightly from one end of the building to the other. Floor maltings began to be phased out in the 1940s in favour of “pneumatic plants”. Here, large industrial fans are used to blow air through the germinating grain beds and to pass hot air through the malt being kilned. Like floor maltings, these pneumatic plants are batch processes, but of considerably greater size, typically 100 ton batches compared with 20 ton batches for floor malting.