Theory

The water in the alcohol-water mixture evaporates and keeps the temperature below the ignition temperature of paper (approximately 230, but science fiction fans might remember this as 'Fahrenheit 451' - the temperature conversion could be an excercise for students). The paper will still be wet with water after the alcohol has burned away. Sodium chloride gives the flame the characteristic orange colour of sodium, which looks like a normal yellow flame.

Extensions

Different proportions of water and alcohol could be tried as could other alcohols.

Further details

The rich and/or confident may wish to try this with a £5 (or bigger!) note. The imaginative will be able to dream up some suitable patter to introduce the demonstration while the silver-tongued may be able to persuade a member of the audience to supply a note for 'burning'.


Safety

Wear eye protection.
A fire extinguisher should be available.