Expert: Peter Loedden - 2/26/2001

Question
my 6 year old daughter is doing a science fair project on what happens to candle wax as it burns. she was curious enough to ask this question. i am not smart enough to answer or find enough material to support a fair project.  please help if you can

thank you,
paul townsend

Answer
Paul,
well, let me see if I can explain this for your daughter.....
First off, when you hang a string halfway into water, after a while more string that actually hangs in the water becomes soaked with water. This is called the capillary effect.
The same thing happens when you light a candle.
When you light the candle the heat from the burning wick melts the wax and the melted wax now, due to the capillary effect, travels up the wick and burns. If you light a wick by itself, without wax, it will burn down pretty quick. So, if the wick is in wax, as in a candle, the wick itself burns much slower, because the molten wax fuels the flame.
One step further, and this is optional: The size of the wick has to be matched to the size of the candle, because a big wick will burn too much wax too fast and the candle will not last very long. If the wick is too small, it can not heat enough wax to feed the wick and more wick burns than wax; the wick will burn off and you'll have a nice candle, but no more wick to light.
Hope that helps and good luck to your daughter in her science project.
Peter