“As a rule of thumb, I never drink caffeine after 3 p.m.”

There are many phrases in our common vernacular that we use every day. Have you ever stopped to think about the origins of some of these phrases? Not surprisingly, the origins of many commonly used phrases can be traced back to the brewing, serving, and consumption of beer. This makes perfect sense, given the fact that beer is largely responsible for the development of modern civilization (but that is a discussion for another day).

Beer in some form has been around since at least 10,000 BC and some historians give beer much credit for the development of modern agriculture and many scientific advances. Temperature control during mashing, fermentation, aging, and serving of modern beer is extremely important to the quality and consistency of the product. However, modern means of measuring temperatures have only been around since the 1700s when the Fahrenheit and Celsius scales were invented along with the mercury thermometer. Prior to these inventions, brewers used other methods to measure temperatures during the brewing process. The mashing process, where crushed grain is mixed with hot water, allows the naturally occurring enzymes in the grain to convert the grain starches into fermentable sugars. The temperature range during the mash plays a large part of how sweet or dry the finished beer will be. Prior to the invention of the thermometer, brewers would test the temperature of the mash by dipping their thumb into the mixture. Through experience and trial and error, veteran brewers were able to determine the temperature of the mash just by using their thumbs. This became known as the rule of thumb.