Candles are fascinating things. They have been the center of many experiments and much research over the years due to how efficiently they burn.
When you look at the flame of a candle you may wonder, where does the wax go? It's a fair enough question. Although the Wax does essentially disappear it's not down to magic.
In this blog, we'll aim to answer that question as simply as we can.
So, we won’t go into too much detail on that. For now, we'll assume if you are reading this you know all about combustion theory......only joking. There may be the odd chemical equation though!
So, first things first, for any flame or fire you need fuel and a wick. These are the two things that allow a flame to form.
- The fuel: made of some sort of wax (Soy, Paraffin, Combo)
- The wick: made of some sort of absorbent twine
The wick, being absorbent, is a key part of how the candle burns.
The wick doesn't actually burn, it needs to absorb and transport the melted wax to the flame. This is called a capillary action.
The liquid wax gets sucked up the wick to where the flame is hottest. It then gets vaporized and burns.
What Happens to The Wax?
Let’s take the example of a Candle that is made from paraffin wax.
This candle would be composed of chains of connected carbon atoms surrounded by hydrogen atoms.
These hydrocarbon molecules can burn completely. When you light a candle, wax near the wick melts into a liquid.
The heat of the flame will vaporize the wax molecules and these would then react with the oxygen in the air.
As wax is consumed, the capillary action we mentioned earlier draws more liquid wax up the wick.
What's key is ensuring the wax doesn't melt away from the flame. Maintaining good candle etiquette will help.
If everything goes the way it should the flame will completely consume it and leave no trace of ash or wax.
This is how the wax of a candle literally vanishes into thin air.
The substances do not disappear. They just change their forms.
The reaction ends, or the candle stops burning when there is either no more fuel (wax) or when there isn't enough heat to melt the wax.
The Equation for Wax Combustion
Whilst the exact equation for wax combustion will depend on the type of wax used (Soy, paraffin etc) the general form remains the same.
Heat will initiate the reaction between a hydrocarbon and oxygen to produce carbon dioxide, water, and energy (heat and light).
According to Anne Marie Helmenstine, Ph.D.
For a paraffin candle, the balanced chemical equation is:
C25H52 + 38 O2 → 25 CO2 + 26 H2O
During the burning process, the carbon combines with the oxygen of the air and forms carbon dioxide gas.
The hydrogen of the wax combines with the oxygen of the air and forms water vapor.
In these two reactions, the wax is consumed and as a result candle’s size goes on decreasing.
There you have it! A simple chemical reaction which transforms one substance form into another a.k.a candle magic.