'Spirits shall be deemed to be at,proof if the volume of the ethyl alcohol contained therein made up to the volume of the spirits with distilled water has a weight equal to that of twelve-thirteenths of a volume of distilled water equal to the volume of the spirits, the volume of each liquid being computed as at fifty-one degrees Fahrenheit'.

In other words. proof spirit meant that the spirit at a temperature of 51°F. weighed exactly twelve- thirteenths of a volume of distilled water equal to the volume of the spirit. It was, in fact. a mixture of spirit and water of a strength of 57.1% of spirit by volume and 42.9% of water.

In the 1740's. the Customs and Excise and the London distillers began to use Clark's hydrometer, an instrument devised to measure spirit strength. A more accurate version by Bartholomew Sikes was universally adopted under the Hydrometer Act,1818, and remained in standard use until 1980.

American British and European 100 deg Proof 50% Alc. vol. 86 deg Proof 43% Alc. vol. 80 deg Proof 40% Alc. vol.

Approximate content Cask In litres Butt 500 Hogshead 250-305 American Barrel 173-191 Quarter 127-159 Octave 45-68

Bottle 70cl Half-bottle 35cl Miniature 5cl

© SWA 1995