The specific gravity (SC) scale measures the sugar content of your beer or wine. The scale is between 0. 760 - 1. 150 take an initial reading before fermentation and one after fermentation is finished to find the alcohol content. The potential abv scale give you the potential alcohol by volume percentage, the reading must be taken before fermentation. The sugar per liter gives you the grams of sugar per liter. The hydrometer is calibrated to give an accurate reading when the liquid is at 68F (20C). to use the hydrometer, fill a Test jar with the sample. You can use the tube that the hydrometer comes with or purchase a Test jar separately. Place the hydrometer in the liquid making sure that it is completely suspended and not touching the sides of the Test jar. Take the reading on the scale at the surface of the liquid.