Hydrometer Use in Wine Making

Hydrometer use in wine making is an invaluable way of tracking fermentation progress and the final alcohol percentage of your beverage. Furthermore, hydrometers allow wine makers to assess if something goes amiss during fermentation such as not enough sugar being available for yeast to turn into alcohol or an unusual taste in their batch.

Hydrometers are long stemmed glass instruments designed to measure specific gravity. Their bulb is weighted on its bottom with either mercury or lead in order to allow it to float upright, and feature a scale printed with specific gravity readings that measure specific gravity, or SG, which measures density by displace ing a certain volume of water at a given temperature. Water is marked at “1.000,” while below it can range from less dense liquids such as kerosene and gasoline to lighter substances like milk and acids; their markings vary between less dense or more than 1.

To take an accurate reading, first sanitize and fill a trial jar – typically the long plastic tube which comes with your hydrometer – with wine/must. Carefully lower the hydrometer into the jar until its reading near zero (zero indicates no sugar) or slightly below (meaning there may be sugar but it has not turned to alcohol). When bottling time comes around subtract the ending fermentation reading to obtain your final alcohol percentage figure.