In the past, "Proof" was a term which signified that the alcohol (when mixed with a small amount of gunpowder and lit) would burn with a consistent blue/red flame. For something to be 100 proof, then it would burn. Anything less would either not burn consistently (such as 80-proof liquors) or would not burn at all.
Presently, "Proof" is calculated based upon the percentage of alcohol in a liquid; 50% alcohol is now considered to be 100-proof. Since beer is only 6-8% alcohol, that would make it 12 to 16 proof....far too low to actually burn. As the remaining items in the beer are primarily water, this is what puts out the flames (as the alcohol is not in sufficient quantities to actually sustain the chemical reaction which is fire).
Hope this little history lesson helps answer your question, Timmy!
|