Function: The hydrometer (with Oechslescale) indicates how many grammes over or under a kilogram a litre of liquid weighs. This is the same as the specific gravity minus 1 000.

The specific gravity of water is 1 000 grammes (1 kg) per litre. This is 0 on the hydrometer (with Oechslescale).

990 grammes is 10 grammes under 1 kg, i.e., minus 10 on the hydrometer (with Oechslescale). Minus readings are taken from the upper coloured scale.

1080 grammes is +80 on the hydrometer (with Oechslescale) on the lower large white scale.

Quality: Select a 300 mm long (preferably German) hydrometer. Do not use a cheap 200-250 mm model. Buy one of the same quality as the Widder range. Test the hydrometer in water to check it reads 0.

Instructions: Pour the liquid to be measured in a tall measuring glass. The type of container is irrelevant as long as it is high enough to allow the hydrometer to float freely. Lower the hydrometer into the liquid. When it is floating freely, a reading is taken at the surface. The white scale indicates + and the coloured shows minus, that is, hydrometer degrees over and under 0.