Wine Institute and WineAmerica are requesting assistance from TTB’s Scientific Services Division for the purpose of determining whether TTB regulations and requirements can be modified so that the temperature at which percentage of alcohol by volume is expressed is consistent with the international standard of 20 degrees Celsius.
Numerous regulations and a US statute define “proof” and “proof gallon” in terms of ethyl alcohol content of a liquid at 60 degrees Fahrenheit.i For wine at least, virtually all other countries have adopted the international standard temperature of 20 degrees Celsius– the US is the only country that still adheres to the temperature of 60 degrees Fahrenheit, or 15.56 degrees Celsius.