what is a hydrometer used for
How to use an Hydrometer. The Hydrometer is best described as a floating weight. It is the most important instrument used by the wine maker or brewer. WHAT CAN AN HYDROMETER DO: The hydrometer is used to determine the âSpecific Gravityâ of the beer or wine either before fermentation begins or at the end of fermentation. It does this by reading the fermentable sugar content in the wort (brewing recipe) or grape juice.