Marty, I used to do a practical with my lower school students where the kids would design and build hot air balloons from crepe paper. These balloons are quite large and need a decent heat source to fill them. The only way to get them to fly at the time was to use metho in an old coke can with holes in the side (about 500 degrees C). The kids soon learnt about the invisable flame from alcohols
. I now use a gel fuel which I enrich to get the correct temp and it is a hell of a lot safer then the original method. Not as much fun though
.
Mark