The Color Of Fire
Colored fire is a common pyrotechnic effect used in stage productions, fireworks and by fire performers the world over. Generally, the color of a flame may be red, orange, blue, yellow, or white, and is dominated by blackbody radiation from soot and steam. When additional chemicals are added to the fuel burning, their atomic emission spectra can affect the frequencies of visible light radiation emitted - in other words, the flame appears in a different color dependent upon the chemical additives. Flame coloring is also a good way to demonstrate how fire changes when subjected to heat and how they also change the matter around them.
The Color Of Fire
To color their flames, pyrotechnicians will generally use metal salts. Specific combinations of fuels and co-solvents are required in order to dissolve the necessary chemicals. Color enhancers (usually chlorine donors) are frequently added too, the most common of which is polyvinyl chloride. A practical use of colored fire is the flame test, where metal cations are tested by placing the sample in a flame and analyzing the color produced.
Emitted colors depend on the electronic configuration of the elements involved. Heat energy from the flame excites electrons to a higher quantum level, and the atoms emit characteristic colors (photons with energies corresponding to the visible spectrum) as they return to lower energy levels 
Flame colorants are becoming popular while camping. Scouts and other outdoor enthusiasts have placed sections of copper pipe with holes drilled throughout and stuffed with garden hose onto campfires to create a variety of flame colors. An easier method of coloring campfires has been fueled by commercial products. These packages of flame colorants are tossed onto a campfire or into a fireplace to produce effects.
Although these chemicals are very effective at imparting their color into an already existing flame, these substances are not flammable alone. To produce a powder or solid that, when lit, produces a colored flame, the necessary steps are more complex. To get a powder to burn satisfactorily, both a fuel and oxidizer will mostly be needed. Common oxidizers include.
When you think of a typical controlled fire, such as a campfire or bonfire, many of the adjectives that come to mind probably concern heat and temperature: Hot. Roaring. Roasting. On the other hand, you may have a number of visual impressions, too: Sparkling. Shimmering. Dancing.
Just as colors appear in a variety of hues, intensities and on physical media such as painting and clothing, they can also present the same apparent range of visual "flavors" when the medium is what you know as fire. This makes sense, since fire is just . . . really hot light. Or is it?
As it happens, the colors you see in fire do correlate with the temperature in fire, so that you can expect to see certain colors more often in hotter flames and others when things are just getting cooking or dying out. But the situation is more complicated than that because exactly what is burning in a given fire also influences the display of colors in the flaming mix.
The range of wavelengths below about 440 nanometers ( 4.4 107 m) includes radio waves at the low end, then microwaves. Above about 7 107 m, X-rays and gamma rays appear; these have high frequencies and are associated with higher energy as a result. This has implications for the colors seen glowing in flames.
The visible light spectrum itself (4.4 107 to 7 107 m) includes radiation perceived by the human eye as, in order, red, orange, yellow, green, blue, indigo and violet (the famous "Roy G. Biv" of elementary-school science classes). As you'll see, this order carries over into fire, albeit with incomplete fidelity.
The reason most fires you're likely to see on Earth burn is that some kind of material is undergoing combustion, and this requires the presence of oxygen gas (O2). Various factors can influence how hot the flame burns, including the nature of the material (obviously, gasoline burns very well; water, not so much) and whether it is being "fueled" with more material and oxygen as the fire grows.
Heat has units of energy and can be conceived as a quantity that moves from regions of higher density to regions of lower density, as with the simple diffusion of molecules. Light and heat are both (generally desirable!) products of fires, and as noted above, light waves are associated with energy in proportion to their frequency. These faster oscillations result in a greater liberation of heat, and this in turn is associated with higher temperatures within and near the flame.
Many materials produce characteristic colors when burned. For example, the element sodium, which combines with chlorine to form ordinary salt (NaCl), produces a bright orange color when burned. Sodium is found in most kinds of wood, so it would be unusual to assemble a fire from the usual branches and sticks and have it not display at least some orange or dark yellow color.
The blue often seen in wood flames comes from the elements carbon and hydrogen, which emit light in the upper end of the visible light spectrum, and thus create blue and violet hues. The metal copper is known to turn green if exposed to the air for long enough; copper compounds create green or blue colors when burned. The metal lithium, to effectively round out the whole rainbow spectrum within this one section, burns red.
Now, you're cooking! So, before getting a look at just what colors to expect of fires burning at a given temperature, it's helpful to know the range of temperatures produced in the sorts of fires you're apt to encounter and scan for colors. After all, this isn't information most people keep inside their heads or someplace handy on their smartphones.
If you have a fireplace in your home that you like to warm your hands over at a discreet distance, the flames providing the heat are roaring away at about 600 C (1,100 F). A bonfire stoked with charcoal and wood can get up to 1,100 C (2,000 F), as can a laboratory Bunsen burner. Of course, the sun's inner temperature of 2,000,000 C (3,600,000 F) makes all of these values seem rather trivial.
As you have learned, both the type of material being burned in a fire and the temperature of a fire influence the colors you see produced. Also, as the example of the two vastly different candle temperatures illustrates, any one fire is almost certain to have a range of temperatures within it (explaining a large amount of the color variation sometimes observed).
When something is heated, it first turns to gas (something you typically cannot observe). These gas molecules then react with the oxygen if they are in fact combustible molecules. It would be typical to see a fire consisting of a uniform material and heated in a controlled way show reddish, then orange and finally bright yellow flames, demonstrating increasing energy and heat released.
If you light and closely study a candle, you will probably note that a sizable portion of the outer core is blue, something not usually seen much in, say, fireplaces. Considering the differences in temperatures given for these fires, this isn't surprising at all.
Of course, one of our favorite parts of making s'mores is roasting the marshmallows over an open fire. We love to watch the flames jump up and down, slowly toasting the marshmallows to golden-brown perfection.
It's easy to get entranced by the flicker of the flames. We enjoy seeing the different colors they take on as they burn brightly. While the majority of the flames hover between the hues of orange and yellow, we also catch glimpses from time to time of other colors, including red, white, and blue. So what causes flames to burn with different colors?
Flames take on different colors for various reasons. Two of the most important factors are temperature and the chemical composition of the fuel. Let's first take a look at the effect temperature has on the color of flames.
There's one other color you may have seen appear in flames on a regular basis: blue. For example, if you have a gas stove at home or have ever seen one operate, you know that the natural gas flames are mainly blue. Likewise, the portion of a flame closest to a candle or a piece of wood might also have blue mixed in with the white.
The color blue indicates a temperature even hotter than white. Blue flames usually appear at a temperature between 2,600º F and 3,000º F. Blue flames have more oxygen and get hotter because gases burn hotter than organic materials, such as wood. When natural gas is ignited in a stove burner, the gases quickly burn at a very high temperature, yielding mainly blue flames.
While variances in temperature account for most of the colors visible in flames, the chemical composition of the fuel can also be a factor. For example, common fossil fuels, such as natural gas and oil, are made up mostly of hydrocarbon compounds, which emit light in the blue spectrum.
Hi, Ahmad! Thanks for sharing your thoughts about this Wonder question! You're right that the chemical reaction does impact the color. We posted the Wonder Sources if you are interested in learning more! :)
Hello, Quinn Haper! Thanks for WONDERing with us! Check out the multimedia images with this WONDER to see examples of the different colors of fire. There is one showing white fire. Happy WONDERing! :)
The colors are based on the flame test in chemistry, which uses a blue alcohol or gas flame. When these chemicals are added to a wood fire, a rainbow effect is more likely due to the chemical composition of the fuel.
Researchers (and volunteer firefighters) Stephen S. Solomon, OD, an optometrist, and James G. King were aware of these perceptual differences when they analyzed accident data from the Dallas Fire Department. In the 1970s and early 1980s, Dallas started replacing its red fire vehicles with lime-yellow fire vehicles with white upper cabs. After the early 1980s, the fire department bought red vehicles with white cabs. During their four-year study published in 1995, Solomon and King found that the risk of visibility-related, multiple vehicle accidents may be as much as three times greater for red or red/white fire trucks compared to lime-yellow/white trucks. The results also showed that when lime-yellow/white fire emergency vehicles were involved in an accident, the likelihood of injury or tow-away damage was less than for red or red/white vehicles involved in an accident. An earlier study by Solomon involving nine cities and 750,000 fire vehicle trips found that lime-yellow fire trucks were half as likely as red trucks to be involved in intersection accidents. 041b061a72