The flames flicker on a candle due to variations in temperature and air density around the flame. These variations create air currents that agitate the flame, giving it an oscillating movement.
A flame is a hot mixture of burning gases, primarily composed of wax vapor, oxygen, and various products resulting from their combustion, such as carbon dioxide and water. At its center, it draws in the melted wax from the wick, which rises by capillarity and vaporizes with heat. This inner region, bluish and cooler, continuously fuels the chemical reaction. As one moves outward from the flame, the oxygen from the outside air causes a more complete combustion and heats significantly more, which is why it appears yellow and bright at its edge. These constant gas exchanges create an unstable dynamic, as different hot gases rise rapidly while cold air rushes in from the sides. It is this turbulent convection movement that gives the flame its characteristic dancing and flickering shape.
The flames move mainly due to air currents, even weak ones. A slight movement of air is enough to alter the shape and height of the flame by changing the amount of oxygen available. The flame seeks to rise because hot gases are lighter, but the surrounding cooler air causes constant thermal exchanges with it. These thermal exchanges make the temperature around the candle unstable and create small vortices. As a result, these small vortices slightly cool certain areas of the flame, causing it to flicker constantly, giving it that typical dancing appearance.
In a flame, rapid chemical reactions produce hot gases that rise, and that’s where things become chaotic. These reactions create locally unstable zones of temperature and gas concentration, leading to a kind of ongoing small-scale struggle between different gas layers. This creates microscopic internal vortices and disturbances known as combustion instabilities, which give the typical dancing and flickering quality of the flame. These internal movements are accentuated by local differences in chemical diffusion, heat, as well as tiny variations in pressure. It’s as if the flame spends its time constantly trying to rebalance itself, never quite succeeding.
The flame of a candle is a continuous mixture of fresh air and hot gases produced by the melted wax. These gases must perfectly mix with the ambient air, rich in oxygen, to burn properly. However, this mixture does not occur in a homogeneous or linear way. There are small fluctuations in the concentration of oxygen or wax vapor: this is called gaseous diffusion. This local variation affects the temperature and density of the present gases, distorting their circulation. The result? The flame oscillates, flickers, and dances incessantly. The more irregular the diffusion, the more agitated and unstable the flame will be, as if it is searching for balance without ever truly finding it.
In microgravity (like in space), flames take on a spherical shape and burn more slowly. This particular phenomenon results from a lack of convection, which profoundly affects how hot gases rise and how oxygen fuels the flame.
The color of a flame indicates its temperature: a blue flame is hotter than a yellow or orange flame. The blue color comes from a complete and more efficient combustion of the fuel.
A lit candle can produce up to 1.5 million tiny soot particles per second. These tiny particles are partly responsible for the orange color of a typical candle flame.
If you bring a cold object, like a metal spoon, close to a candle flame, the flame appears to be drawn towards the object. This is due to the fact that the local drop in temperature creates a convection current, thereby altering the shape and direction of the flame.
A flickering flame is usually a sign of drafts or instability in the combustion. This phenomenon itself is not dangerous, but it indicates that the flame can be more easily blown out or dispersed. It is therefore advisable to check the conditions around the candle to avoid any incidents.
Sure, absolutely. A larger wick provides more fuel (melted wax) to the flame, thereby increasing its size, brightness, and dynamic instability. This can cause the flame to dance more in response to even a slight draft or local variations in oxygen.
The sudden extinguishing of a flame often results from a brief interruption in the supply of oxygen or fuel. This can occur due to air turbulence, a sudden draft, or because the wick can no longer draw enough melted wax to sustain the flame.
The base of a flame is blue due to complete and hotter combustion, resulting from a sufficient amount of oxygen. This produces fewer glowing carbon particles than at the top of the flame, which is why it has the characteristic bluish color.
A flame producing black smoke generally means that your candle is lacking oxygen or that the combustion is not fully optimized. Commonly, reducing the wick size or ensuring better air circulation around the flame is enough to correct this issue.
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