Why do they have rakes? I always thought the whole point of lautering was to get the grain bed to act as a filter. Wouldn't running a rake through it be counterproductive?
Originally Posted by Wikipedia
A quality lauter tun has rotating rake arms with a central drive unit. Depending on the size of the lauter tun, there can be between two and six rake arms. Cutting blades hang from these arms. The blade is usually wavy and has a plough-like foot. Each blade has its own path around the tun and the whole rake assembly can be raised and lowered. Attached to each of these arms is a flap which can be raised and lowered for pushing the spent grains out of the tun. The brewer, or better yet an automated system, can raise and lower the rake arms depending on the turbidity (cloudiness) of the run-off, and the tightness of the grain bed, as measured by the pressure difference between the top and bottom of the grain bed.
Found that on Wikipedia and it sounds to me like it's just to prevent a stuck sparge, but I didn't think that stuck sparges are that much of a problem if you were careful. Maybe because of the amount of grain they're working with they have to be more careful with their grain beds compacting? Or is it just to make it easier to get the spent grain out of the tun?