Why are Bonfire Flames Orange?

Question

My wife and I were having a great bonfine yesterday (Sunday) and she noticed that the flames were Orange and asked me why, but I could not give her an answer. We were burning garden waste & old wood, it was when all this was well lit that the orange flames were most noticable. Any one out there know why?

Answer 1

Let's get technical. All color that you see is composed of photons, tiny packets of mass-less energy traveling at the speed of light. When fuels are burned, part of the combustion energy agitates electrons driving them up into higher more energetic orbits around atoms and molecules. When the electrons fall back into rest orbits in one or more steps the excess energy is converted into visible and invisible (infrared and ultraviolet) light or photons. The color you see depends on the wavelengths of most of the photons where low energy is infrared (heat), visible light is medium energy and ultraviolet is highly energetic (and can even cause sunburns!). The orange light you see is fairly low energy but visible photons near red (as in embers). The actual photons depend on the specific chemical reaction (what is being burned) and the maximum temperature reached. Very high temperatures cause more highly energetic photons as in a light bulb filament. A blacksmith can bellows air (oxygen) on a coal fire causing a very hot flame and near white light. The orange flame of a wood fire results from incomplete combustion of carbon which though very hot will survive to form soot. If the carbon is completely combusted it will form carbon dioxide (CO2) a gas instead.

Answer 2

It is the radiation colour from unburned carbon. If the fire had enough oxygen in the flame to completely burn the fuel it would burn blue. you can see the same thing on a gas stove when the air mix is to lean. A bonfire is turning more fuel into gas (pyrolyzation) than it can get O2 to burn from the air around it. If you see huge oil fires on the news they do the same thing. An oil lamp without it's chimney on to create increased airflow burns with a sooty orange flame also.

Answer 3

Nothing to do with the temperature, just the massive ammounts of sodium ions in your bonfire material. Sodium burns with an orange / yellow flame, this is what you are seeing.
throw a load of copper wire on, the flames will become blue/green, this is the colour of heated copper ions

Answer 4

When energy is introduced into certain atoms (such as chemical energy released due to rapid oxidation, which is called "burning") some of that energy excites the electrons in these atoms, causing them to jump into higher orbitals. When they return to their original orbitals they release back energy in the visible light range (and other ranges also). We see this as orange light. This branch of knowledge is called Quantum Physics (or Quentum Mechanics).

Answer 5

Yes! Different gases burn at different temperatures and the color of the flames is a rough indicator of the temp. The bluer the flame, the hotter it is, until it turns white. Orange is almost always wood fire and soft waste. Cooler and more ash from unburned material.