My lovely bride worked for the University of California library system on the Berkeley campus for many years. She was always bringing home discarded reference books and other treasures. One of my favorites is the third edition (1959) of Louis De Vries' German-English Science Dictionary for Students in Chemistry, Physics, Biology, Agriculture, and Related Sciences. I figure that includes brewing! On p. 492 Prof. De Vries defines "Vorlauf" as "first runnings, heads." When you run the wort off the mash, the so-called "first runnings" are the richest in sugar content. The sweet, viscous liquid is the portion of the wort with the highest specific gravity. It also contains much undesirable material--proteins, grist debris, unfermentables--that ideally should be separated from the kettle liquor. One of the ways to do this is to re-circulate the "heads" by running it through the grain bed one more time. The porridge-like mash acts as a filter and helps clarify the wort. You can actually see this if you take a sample in a glass and hold it to the light. My Dictionary of Beer and Brewing (2nd ed., Rabin & Forget) defines "vorlauf" on p. 275 as "German term for recirculation of wort through the grain bed." I noted in my first tasting that the Summerfest had a cloudy appearance that I hoped might disappear with time. Alas, it has not. Looking over my session notes, I see that I neglected the "vorlauf" stage! I just ran the wort off, sparged the grains, and cooked away. Much of the haze-causing material settles out in the boil, especially if it can be strained through a bed of spent hops. I do this by having a colander-like false bottom in my kettle, and after the brew is chilled it drains through the sieve into the carboy. Lots of gunky stuff sticks to the hops and does not get into the finished beer. I pride myself on bright, clear beers, so this one is a little disappointing, despite the fact that it tastes great and is very refreshing. So, all you brewers out there, don't forget to vorlauf.
a.d. XIII Kal. Aug.