What is the minimum percentage of ethanol, in a drink, that can be ignited by a match?
Anecdotally, I believe it to be 50% or 100 proof.
From personal experience, I’ve ignited gently-warmed glasses of brandy before (80 proof). I’ve also exploded amaretto (56 proof), but that was in a hot frying pan. I suspect it won’t ignite at room temperature.
At room temp, it has to be 50% (100 proof.) If it has a large amount of sugar in it, you might be able to get away with a little lower. When heated, however, lower proofs have alcohol vapor that can float up from the cooking vessel and be ignited.
Well wait a minute, I recall lighting vodka on fire and it is usually 40%. I don’t have any here otherwise I’d try it. Am I missing something?
A few people have posted that it has to be 100 proof to light. This is incorrect. It has to be 100 degrees proof (English system), which is equivalent to 114.2 proof (US), or 57.1% ethanol by volume.
At 51 deg. Farenheit (10.6 deg C), 57.1% ABV mixture will light.
Temperature can change this significantly.
Wikipedia’s Proof article
You’re not missing anything. 40% will sometimes ignite and sometimes burn, especially given an evaporative medium (like a cotton swab saturated with vodka will burn off the vodka really well)