Lautering is the process of separating sweet wort from spent grain after the mash. The word comes from the German läutern, which means to clarify, clear, or refine. In lautering, the grain bed acts as a filter, allowing the wort to run off while keeping mash solids out of the brew kettle. Lautering is easy in theory, but it isn’t always straightforward in practice. Here are three tips for smooth lautering.
Check your crush.
Barley husks provide the filter that separates sweet wort from particulates. Good lautering, then, depends on those husks remaining as intact as possible. Unfortunately, increased husk integrity sometimes requires a coarser crush, which can reduce extract efficiency in the mash. Experiment with your crush to find a balance between mash efficiency and lautering quality.
Lauter as slowly as you have to.
One of the best ways to guarantee a stuck mash is to open the valve on your mash/lauter tun (MLT) and let ‘er rip. Good lautering cannot be rushed. The trick is to go as fast as you can, but no faster, and this depends on the interplay between your own MLT and the particular grist you’re trying to lauter. Open the valve slowly at first to establish a good flow, and then gradually open it further if you can do so without gumming up the works.
Use rice hulls if needed.
Some grists, especially those high in wheat, rye, or oats, are just stuck mashes waiting to happen. One way to improve lautering with these grains is to add half a pound or more of rice hulls to the mash. Rice hulls are tasteless and inert, but they can be your best friend if you frequently brew oatmeal stout or Bavarian style Hefeweizen. Think of rice hulls as dietary fiber for the mash.
Lautering efficiency also depends on the particular geometry of your mash/lauter tun. Those who practice continuous sparging (also called fly sparging) will almost certainly use a false bottom, while homebrewers who batch sparge might also consider a braid, screen, slotted manifold, or other filter. You’ll have to experiment with your system to figure out what works best for you.