Using a Hydrometer for Fermentation Control

Utilizing a hydrometer for fermentation control is a fundamental skill of any brewer. You use it to monitor the progress of your brewing process by monitoring how much sugar is being converted by yeast into alcohol in a given liquid, and adjust as necessary so as to meet desired alcohol content and flavor profile of beer.

Hydrometers are long, thin glass tubes fitted with a weighted end at their bottom and two to three graduation scales running along their length, often used to test wine, beer and other alcoholic beverages. Hydrometers work by measuring density relative to water density based on its temperature setting – their accuracy increases accordingly when testing liquid temperatures differ significantly between testing samples.

To use a hydrometer effectively, begin by thoroughly cleaning it. Next, gently lower it into the liquid in which you intend to measure, giving it a gentle spin to dislodge any trapped bubbles on its way through and looking for where its surface curves up around its stem forming what’s known as a meniscus; reading from eye level is best to reduce parallax errors.

Most hydrometers will come equipped with instructions on how to calibrate them for different pressure levels and temperatures, making this step essential if brewing at sea level or high in the mountains where atmospheric pressure varies widely from standard. Furthermore, recalibration may be required after extended storage or extensive usage.