🏷️ Oechsle scale

The Oechsle scale measures the must weight of grape must, that is, its specific gravity, in degrees Oechsle (°Oe). The German Wine Institute explains it as a comparison of the weight of one litre of must with one litre of water at 20 °C. It is determined with a must scale or a calibrated refractometer.

The value mainly reflects the sugar in the must, which decides the alcohol of the finished wine. Sugar rises as grapes ripen. In berries affected by noble rot (Botrytis cinerea), water evaporates on sunny days and the sugar is concentrated further. A higher must weight therefore goes with a higher quality or Prädikat level.

The unit is named after Ferdinand Oechsle, a pharmacist and mechanic from Württemberg, who invented the must scale in 1836.

In Germany the must weight underlies the Prädikat levels of Prädikatswein. The Wine Institute states that each of the six Prädikate has a minimum must weight that depends on grape variety and growing region, with stricter requirements usually in the warmer south. Its examples are 83 to 100 °Oe for Auslese and 110 to 128 °Oe for Eiswein, depending on the region. The Wine Act itself sets the actual alcohol minimum (7% vol. for Kabinett, Spätlese and Auslese, 5.5% vol. for Beerenauslese, Trockenbeerenauslese and Eiswein) and leaves the natural minimum alcohol per Prädikat to the state governments, not below 9.5% vol. in wine-growing zone A.