This unit of measurement (also known as specific gravity) describes the ratio of two densities as a dimensionless ratio. In viticulture, the weight ratio between the volume mass of wine or grape must and the same volume mass of water (with a density of 1.000) is determined at a measuring temperature of 20 °Celsius. In the case of grape must, this is also known as the must weight. The result is given to four decimal places and is represented by the code "d" (for density) or "d20/20". The notation "20/20" means that the measurement was carried out at 20 °C and the measuring device is calibrated to the same temperature (20 °C).
The relative density value is analysed during quality wine tests and, if the result is positive, is mandatory for the award of the official test number (Germany) or the state test number (Austria). Among other things, the total extract and the alcohol content of the wine are determined.
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Dominik Trick
Technischer Lehrer, staatl. geprüfter Sommelier, Hotelfachschule Heidelberg