Why when we light a candle, the flame is shaped like a teardrop?

Interestingly, a candle flame is teardrop shaped on Earth, but spherical in space .

According to the National Candle Association (headquartered in Washington DC, USA), there are many chemical and physical theories behind the beauty and light of candle flames. In fact, scientists have been "fascinated" by candles for over 100 years and are always looking for explanations for the phenomena related to it.

In 1860, scientist Michael Faraday gave a series of now-famous lectures on the chemical history of candles, demonstrating dozens of scientific principles through his careful observations of burning candles.

In the late 1990s, NASA took candle research to a new level when it conducted experiments on the space shuttle to study candle flames in a zero-gravity environment.

Scientists at many universities and research institutes around the world also continue to conduct experiments with candles to learn more about candle flames, emissions, and combustion.

How does a candle burn?

All waxes are essentially hydrocarbons, meaning they are composed largely of hydrogen (H) and carbon (C) atoms.

When you light a candle, the heat of the flame melts the wax near the wick. This liquid wax then moves up the wick through capillary action.

The heat of the flame vaporizes the liquid wax (turning it into a hot gas) and begins to break down the hydrocarbons into hydrogen and carbon molecules. These molecules are carried up into the flame, where they react with oxygen from the air to produce heat, light, water vapor (H ₂ O), and carbon dioxide (CO ₂ ).

It takes a few minutes from the time you light the candle for the burning process to stabilize. (Photo: pixels)

Enough heat will be generated to melt more wax, to keep the burning process going.

It takes a few minutes after you light the candle for the flame to stabilize. The flame may flicker or smoke a little at first, but as it stabilizes, the flame will form a teardrop shape.

If too little or too much air/fuel is received, the flame may flicker or flare up, with unburned carbon particles (soot) escaping from the flame before they can burn completely.

The puffs of smoke you sometimes see when a candle flickers are actually unburned soot particles escaping from the flame due to incomplete combustion.

Color of candle flame

If you look closely at a candle flame, you will see that it is divided into three basic color zones: The blue zone at the base of the flame . Next is the small orange/dark brown zone, and finally the large yellow zone that we usually associate with "candle flame".

The oxygen-rich blue region is where hydrocarbon molecules vaporize and begin to split into hydrogen and carbon atoms. Hydrogen is the first atom to split here and reacts with oxygen to form water vapor. Some of the carbon atoms burn to form carbon dioxide.

Candle flames are divided into three basic color zones. (Photo: Pinterest)

The orange/dark brown region has relatively little oxygen. This is where the different forms of carbon continue to decompose, and small, hard carbon particles begin to form.

At the base of the yellow region, the formation of carbon particles (soot) increases. As these particles rise, they continue to heat up until they catch fire and emit the spectrum of light we see.

Because the yellow part of the spectrum is most dominant, when carbon burns, the human eye perceives the flame as slightly yellow.

In addition to the three basic color zones above, the candle flame also has a fourth color zone. This is the light blue border outside the candle flame, extending from the blue zone at the base of the flame upwards.

Why do candle flames have a teardrop shape?

As the candle burns, the flame heats the air around it and begins to rise. As this hot air moves upward, cooler air and oxygen rush to the base of the flame to replace it. This continuous cycle of air moving around the flame (convection currents) gives the flame its elongated or teardrop shape .

A spherical candle flame in space. (Photo: Pinterest)

Since the "up" and "down" movement of air flow here comes from the effects of gravity on Earth, scientists have wondered what a candle flame would look like in space, where gravity is at its smallest.

In the late 1990s, NASA scientists conducted some experiments on the space shuttle to see how flames would behave in microgravity. As we can see from the NASA photo above, candle flames in microgravity are spherical in shape, rather than the elongated shape they have on Earth. In other words, on Earth, flames rise vertically, but in space, they spread out in all directions.