“How do we know what we think we know?” This line from the opening sequence of the movie Run Lola Run might sound like little more than philosophical brooding, but for brewers large and small, it’s a question with legitimate and practical implications. Accurate measurement lies at the heart of brewing: Without it, repeatability is nearly impossible.
Temperature measurement, or thermometry, is one of the most critical process steps of any brew day. From heating strike water and mashing in to cooling wort and maintaining fermentation, good beer requires good temperature measurement.
Today we’re lucky enough to have access to reliable, accurate thermometers, but this wasn’t always the case. In fact, decoction mashing partly developed as a way to predictably raise the temperature of a mash when thermometers left much to be desired. Because water boils at a fixed temperature at a given elevation, adding boiling water (or boiling mash) to the main mash could achieve a desired temperature change even in the absence of good temperature data.