If you undersparge, you leave usable sugars behind in the grain bed. If you oversparge, you extract an excessive amount of tannins. When brewing a session beer, collecting the proper volume of wort allows you to get a reasonable extract efficiency and brew a beer that isn’t astringent.

Session beers allow beer drinkers to enjoy “a few” without becoming overly intoxicated. They are low-gravity, low-alcohol beers for extended drinking sessions. Brewers can  — and, of course, have — differed over exactly how low in alcohol a beer needs to be in order to qualify as a session beer. For the sake of this article, let’s say session beers are those under 4.5% ABV. (And outside of this article, feel free to apply your own definition.)

Just because these are “little” beers, however, doesn’t mean that they don’t require our full attention. One of the biggest potential problems when brewing a session beer is oversparging. With a smaller malt bill, collecting your full pre-boil wort volume may mean you’ve sparged past the point that tannins become much more soluble. Oversparging in this manner results in beer with an astringent mouthfeel. This is frequently described as the puckering, bitter-like feeling one experiences when drinking tea. [Read more…]