Why brief contact with a flame doesn't burn?

12 October 2008

Question

Why can a finger be passed through a flame and not burn?

Answer

Kat - This is a fascinating thing to see. The first time I saw this done was by my vicar at church. I really thought, 'This man has come from God!' It was very impressive! The thing behind this is that basically candles aren't that hot. The other trick is to do it fast and through the right part of the flame. You need to know a little bit about how candles work. It all boils down to convection, heat rises. The top of the candle is much hotter than the bottom of the candle. If you ever try holding your hand over the top of the candle you find out extremely fast it's very, very hot. It's about 600 degrees. You can actually pass your hand through the bottom of the flame because all the hot air is rising up the bottom of the flame is where all the cold air from the room is being sucked in. The bottom of the flame is quite cold. You can stick your hand through, get a bit of soot on it. You can do that so long as you do it at quite a quick speed, especially if your fingers are a bit wet. Then you'll just burn off the water rather than burning your hand.

Chris - Great, so now you can go and impress your mates with that but don't try it with a blow-torch or something!

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