The hydrometer makes use of Archimedes' principle: a solid suspended in a fluid is buoyed by a force equal to the weight of the fluid displaced by the submerged part of the suspended solid. The lower the density of the fluid, the deeper a hydrometer of a given weight sinks; the stem is calibrated to give a numerical reading.
What is an Alcoholmeter?
An alcoholmeter is a hydrometer that indicates the alcoholic strength of liquids by percentage. It is also known as a proof and Tralles hydrometer. It measures the density of the fluid. You use a graduated cylinder and place the hydrometer in the fluid to measure the alcohol by volume percentage.
Alcoholometers have scales marked with volume percents of "potential alcohol", based on a pre-calculated specific gravity. A higher "potential alcohol" reading on this scale is caused by the amount of converted sugars to alcohol. A reading is taken before, during and after fermentation. The approximate alcohol content is determined by how the number decreases from the original density of the sake.
Measure each stage in the Sake brewing process at a consistent room temp of 70 degrees Fahrenheit. Your first measurement should be just before adding the yeast. The density for the original gravity reading will be higher with the measurements on the side of the hydrometer. Using an ABV calculator you can get the percentage of alcohol from the original gravity reading compared to the final gravity reading.
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