How Do Candles Work?

Candles have been around for thousands of years, and this illumination device isn’t going anywhere anytime soon. While candles are very simple compared to other sources of light such as electricity, few people actually know how these classic devices work. Below, we explain how candles work, how the colors of the flame indicate each stage of combustion, and which types of waxes lead to a better burn.

How do candles work?

Candles are powered by combustion reactions. When you light a candle wick, the wax around the base of the wick melts. Through capillary action, this liquid hot wax is drawn up the wick. The heat of the flame turns the wax into a hot gas (a.k.a. vaporizes it) and starts to break down the wax into molecules of hydrogen and oxygen. These vaporized molecules react with oxygen from the air to create heat, light, water vapor (H2O) and carbon dioxide (CO2).

About 25% of the energy generated through this combustion reaction is released as heat. This heat melts still more wax, creating more fuel for the combustion reaction. The combustion reaction will continue until the wick burns down or all the wax is used up, whichever happens first (or until you blow out the candle, of course).

When you first light the candle, it can take a few minutes for the combustion reaction to stabilize. This is why a candle flame sometimes flickers a lot when you first light it. As long as the wick is trimmed properly, the flame should stabilize after a few minutes and burn steadily in a nice teardrop shape.

hands holding candle in dark

Why do candle flames have different colors?

If you look closely, you’ll notice that the candle flame isn’t the same uniform color. That’s because candle flames have several different zones of heat. The bluish color at the base of the flame is where the hydrocarbon molecules vaporize and start to break apart into hydrogen and carbon atoms. There’s a lot of oxygen in this zone, so the hydrogen starts to react with it to form water vapor. Some of the carbon atoms in this zone may also begin to burn to form carbon dioxide.

The middle part of the flame will be a dark orange-brown due to the relative absence of oxygen. In this area, carbon continues to break down. It also begins to form tiny hardened particles that are heated to approximately 1000 degrees Centigrade as they rise up through the flame.

Next is the yellow zone, which forms the bulk of the flame and gives it the classic golden color. In this zone, more and more carbon particles are created, which can lead to the formation of soot. These particles continue to heat until they ignite, emitting the full spectrum of light, with yellow being the most dominant to the human eye.

The final zone is the veil, a.k.a. the faint blue edge that surrounds the flame. This is the hottest part of the flame and is created when the hydrogen and carbon released from the combustion reaction meet the oxygen in the air.

trio of candles on countertop

Does the type of candle wax matter?

While all types of candle waxes are basically hydrocarbons, different types of waxes contain different additives and formulations, which affect the candle’s performance. For example, heating paraffin wax releases soot and 11 known toxins — two of which are carcinogens — into the air. All-natural waxes such as soy and coconut have a cleaner burn.

Different waxes don’t just provide cleaner burns, some also provide longer burn times for the same amount of wax, making your candle last longer. Generally speaking, soy waxes provide an excellent balance between clean, low-soot burns and longer burn times. See our guide to learn more about what candles are made of and the different types of wax, like our coconut wax candles.

Our standard 13.75 oz. soy candles provide 60-80 hours of burn, depending on how well you take care of your candle. Trimming your wick, keeping a lit candle away from drafts, and other candle care tips will also prolong the life of your candle.

Learning how candles work will give you a better appreciation of just how amazing these inventions are. Whether you’re using candles for illumination or simply to release their amazing fragrances, knowing how they work will enhance your experience.