What do the colors of a candle flame mean?

Ever wonder what’s really going on when you light a candle? The answer is a lot, actually.

The heat from the flame melts the candle wax below and draws it up through the wick. Just like when you hang a cloth on the edge of the sink and it begins to soak the water up the length of the cloth, the same principle happens here with the law of capillary attraction.

The candle flame gets hot enough to vaporize the wax and convert it into a gas of carbon dioxide and water vapor.

It’s not uncommon for a candle flame to flicker and shine the first couple minutes as the combustion process normalizes.

With the flame burning properly, you’ll begin to notice a few color characteristics to the flame.

BLUE BASE AND VEIL

At the base of the candle flame is a blue area. This is where the hydrocarbon molecules are heated to the point they vaporize. It’s an oxygen rich area and the molecules begin to separate with temperatures reaching up to 2500° Fahrenheit. This is the hottest part of the candle, but it’s also concentrated.

Although it’s virtually invisible, there is also a blue “veil” that surrounds the entire flame. It exists simply because it’s exposed to oxygen on all sides. This thin “veil”, like the blue base, can reach over 2500° Fahrenheit.

ORANGE/BROWN

Just above the blue area, you begin to see a brownish/orange area. Here is where you experience the crackling sound (Pyrolysis) from a candle as the fuel looses oxygen. This in turn creates minute particles at about 1800° Fahrenheit.
YELLOW

As we work our way up the candle flame, carbon particles increase and rise upwards until they combust/ignite to create the yellow luminescence light where carbon particles start forming around 1400° Fahrenheit.

CLOSING NOTES

Now, here’s something that will mess with your mind. If the blue area of the flame is the hottest (including the veil), why is it easier to light another match or candle from the top of another candle flame? Answer: the top of the candle flame is like a mini jet, feeding a constant stream of heated gasses. Think of it like a little jet engine. At the base of your candle resides a sort of “rested” pool of oxygen rich combustion. Although it’s hotter at the base, it’s the steady stream of hot gasses at the top that conducts heat transference better.

Lastly, if you’ve ever watched black smoke and soot rise from a flickering flame, the reason is quite simple. The flame is cooling so combustion is reduced, releasing particulates.