Candles have been used for millenniums and were first thought to have been made by the Romans in 500BC. Candles have not changed much in the 2500 years since they were first invented.
This proves that they must have a fairly simple, yet successful and effective structure.
Let's face it, almost every home in the world will have at least 1 candle in it: whether it is used for brightening a room or for leaving a scented aroma floating in one’s home.
Despite us all knowing what candles are and that we use them regularly… most of us probably don’t actually know how a candle works!
If this has been playing on your mind, then keep reading!
How does a Candle Work / How do Candles Burn?
There are two parts to how a Candle actually burns.
1- Fuel - the wax (of some sort)
2- Wick - an absorbent twine/string
The wick needs to be absorbent so it can take in liquid wax and push it up while the wick continues to burn. The reason the wick doesn’t completely disintegrate is due to this vaporized wax cooling the wick and protecting it against the flame.
Waxes are hydrocarbons, meaning they are made up of both elements; Hydrogen and Carbon atoms.
When you light the wick, the liquid wax is drawn up the wick by a capillary action. The heat from the flame vaporizes the liquid wax, and turns it to hot gas. This is when it starts to break down the hydrocarbons, into hydrogen and carbon.
The action of these molecules reaching the flame then reacting with oxygen is what creates heat, light, carbon dioxide and water vapour.
During the combustion process, the heat is so great, that it radiates back to melt all of the wax until no fuel is physically left. The candle will stop producing heat and light once all of the fuel (wax) has been vapourised.
A silent burning candle is one of the most efficient combustion machines if the air feeding the flame is consistent and constant. However, if there is a big fluctuation in air flow, such as a gust of wind, it will cause the flame to flicker and could cause uneven burning of the wax candle.
Candles burn downwards as there is a continuous cycle of rising hot air and sinking cold air.
This cycle occurs due to the flame from the candle heats the air around it, and the air begins to rise.
As warm air moves up, the cooler air and oxygen replaces the risen hot air. This is because cold air is much denser than warm air. Hence the infinite cycle of rising and descending air.
Its hard to believe that this concept has been used for thousands of years!
It’s also important to remember good candle etiquette whenever you are burning.
How do Scented Candles work?
There is a lot of science involved within the burning process of candles. Even more when it comes to the process of how the smell of scented candles spreads from room to room, otherwise known as diffusion.
When you light one of your sensual scented candles, you may notice that after each hour that passed, the same smell follows you through your home, getting stronger and more distinct. This process is called diffusion (the intermingling of substances by the natural movement of their particles).
Gas particles are released once the flame of the candle starts to burn through the wax fuel.
Once released, these gaseous particles move at random speeds and different directions. The particles will continue to move through the air and disperse randomly until they have used all of their Kinetic energy (the energy needed for motion).
A Candle is a perfect instrument for aiding the diffusion of fragrances. One of the key elements of dispersal is high temperatures. The higher the temperature, the more the particles will move and create kinetic energy. This is what allows the scent particles to travel rapidly through your house.
Candles obviously have a key heat force (flame), therefore this will ensure the transfer of energy once the scented wax has melted and turned to gas.
Diffusion also occurs when a high concentration of gasses or particles (in this case fragrance), moves to an area of low concentration.
In this scenario, using scented candles, the air around the candle will hold a very high concentration of perfume. This then diffuses to areas which have low concentration of these fragrances.
This is the process of how scents move room to room.
I hope this has satisfied your curiosity of Candles; How they work and how they burn.