Jumping Flames

04 November 2007

Ingredients

A Candle A candle with a good wick A Lighter Something to light it with

Instructions

LIght the smokeLight the candle and wait until it is burning well and has a glowing ember at the end, it works better when the wick is too long.

Carefully pour the excess wax out of the candle.

Blow the candle out gently.

Quickly wave the lit lighter near to but not next to the candle. It works best if you wave it in the smoke.

Result

With any luck the candle should relight without being touched by the flame

Explanation

It is very difficult to set light to a lump of solid or even liquid wax because the surface area is very low so it can't react with oxygen very fast however it just takes a match to light a candle.

A candle works by melting the wax which is then drawn up the string like wick  by capillary action. The wick is heated by the flame and has a large surface area so the wax vapourises. Now the wax has a huge surface area because it is a gas and it has enough energy to start reacting with the oxgyen in the air to burn.

A Candle A candle
A candle consists of a wax cylinder with a wick through the centre. The flame melts a pool of wax at the top. The molten wax is drawn up the wick where it evaporates and then burns with the oxygen in the air.

When you blow out the candle the wick is still hot so the wax continues to evaporate for a few seconds. Eventually this wax condenses into a cloud of tiny wax particles we call smoke.

If you bring another flame to the vapour it can still burn so it will relight the candle.

Blown out Candle Reigniting the Candle
The wax continues to evaporate condensing again to form a cloud of smoke. The vapour is very flammable so you can relight it.

This is why petrol is much more dangerous than diesel even though it will catch fire at a lower temperature.  Petrol has a much lower boiling point and so will vapourise much more easily, this means there is much more vapour to light if there is a spark.

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