h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Hello, the thing with proof being twice the alcohol by volume is an American simplification of the much older British method.

Basically gunpowder soaked in water doesn't light, gunpower soaked in alcohol does. Mixtures of water and alcohol may or may not, depending on the ratios. 100% proof is the most watery mix that the gunpower will still burn. I can't remember exactly what this is, but I think it's about 55 to 60% by volume, and I think pure alcohol is about 170-175% proof.

So whilst the footnote is true for the colonies, it's not for the UK.

Bez

Is proof a description of how much extra alcohol or water is needed to either prevent or start an ignition?

My understanding is that proof spirit was held to be that which if poured over gunpowder and ignited would eventually ignite the powder. So presumably the proportion of water which could be present and still allow the gunpowder to ignite would depend on the gunpowder.

Later, however, proof spirit was a term applied until 1980 as a basis for customs and excise purposes - ie taxation. Proof spirit was legally defined as having 49.2% of alcohol by weight, 57.1% by volume, at 51 deg F (10.5 deg C).

Proof seems to be only one particular threshhold, and not a continuous measure-anything which has more alchohol in it also results in ignition and is merely called proof?

How do the percentages come in?

I think the definition is something like "burns with a steady blue flame and ignites the powder". Until the advent of hygrometers there was just proof, overproof and underproof, without degrees of measure.

The definitions are, indeed, different in the UK and US. As h2g2 is based on UK terms, it should really be changed. In the UK, 100% ABV is 175 proof.

I also found this calculator: http://www.ex.ac.uk/cimt/dictunit/ccalcoh4.htm