Lautering

Lore & Background

The lauter tun is the traditional vessel used for separation of the extracted wort. While the basic principle of its operation has remained the same since its first use, technological advances have led to better designed lauter tuns capable of quicker and more complete extraction of the sugars from the grain. The false bottom in a lauter tun has thin slits to hold back solids and allow liquids to pass through; the solids themselves form a filtration medium. The false bottom of today's lauter tun is made of wedge wire, which can provide a free-flow surface of up to 12% of the bottom of the tun.

Run-off tubes are evenly distributed across the bottom, with one tube servicing about 1 m² of area. These tubes typically have a wide, shallow cone around them to prevent compaction of the grain directly above the outlet. In the past, run-off tubes flowed through swan-neck valves into a wort collection grant, but this system led to a lot of oxygen uptake and has mostly been replaced by a central wort-collection vessel or concentric zone collection pipes. Brewhouses in plain public view, particularly those in brewpubs, often maintain the swan-neck valves and grant for their visual effect.

A good quality lauter tun has rotating rake arms with a central drive unit, with between two and six rake arms. Cutting blades hang from these arms, each with its own path around the tun, and the whole rake assembly can be raised and lowered. Attached to each arm is a flap for pushing spent grains out of the tun. The brewer or an automated system can raise and lower the rake arms depending on the turbidity of the run-off and the tightness of the grain bed. There must be a system for introducing sparge water, most often a ring of spray heads that ensure even and gentle introduction without beating down on the grain bed.

Reader's Guide

Lautering is significant as the step that produces the clear liquid wort from which beer is fermented, and its three steps—mashout, recirculation, and sparging—each serve a distinct purpose. Mashout raises the mash temperature to 77 °C (170 °F) to stop enzymatic conversion and improve fluidity, and is considered especially necessary when the water-to-grain ratio is low or when the grain contains more than 25% wheat or oats. Recirculation draws off wort from the bottom and adds it to the top, using the mash itself as a filter, monitored by a turbidimeter. Sparging trickles water through the grain to extract sugars; it is a delicate step because the wrong temperature or pH will extract tannins from the chaff, resulting in a bitter brew. Two sparging methods are described: English sparging (batch sparging), which drains the wort completely, adds more water, holds it at 76 °C (169 °F), and drains again; and fly sparging (German sparging), a continuous process used by commercial breweries and many homebrewers that yields greater sugar extraction. The lauter tun's design—including false bottoms, run-off tubes, rake arms, and sparge water systems—has evolved to improve efficiency and clarity, though some traditional visual elements like swan-neck valves are retained in brewpubs. Some small breweries use a combination mash/lauter tun, but the rake system cannot be implemented because the mixing mechanism for mashing is of higher importance.

Did You Know?

• Mashout is considered especially necessary if there is less than 3 liters of water per kilogram of grain, or if the grain is more than 25% wheat or oats.
• The false bottom in a lauter tun has thin slits of 0.7 to 1.1 mm to hold back solids, but the solids themselves form the filtration medium.
• English sparging drains the wort completely, then adds water held at 76 °C (169 °F) for a second draining that can be used to make small beer.
• Fly sparging uses a continuous process where water is added at the same slow rate that wort is drained, resulting in greater yields.