If you do much camping, have to deal with a lot of power outages or simply like to save on your electric bill, you may be quite familiar with the gas lantern.

Have you ever wondered how this device works?Now, you'll learn all about what's going on inside a gas lantern!

Incandescence
Have you ever seen a heated horseshoe? Maybe at a blacksmith shop or on
TV? If so, you know that if you get a horseshoe hot enough, it starts to glow. If you get its temperature up to 400 or 500 degrees F (about 230 degrees C), it will glow a dull red. Get the temperature up to about 1,000 degrees F (538 degrees C) and it's a bright orange -- you see this temperature all the time in the coils of an electric stove, oven or toaster. In these appliances, electricity heats a coil or wire hot enough to make it glow. If you get the temperature up to about 4,500 degrees F (2,500 degrees C), you get a very bright yellow (nearly white) color. That's the temperature of a normal light bulb filament.

When something produces light because of heat, it is said to be incandescent. Anything that you heat up will glow, but different materials are better or worse at producing light as they are heated. Steel is a pretty good producer of light. Glass is a very poor producer. If you heat glass it will glow, but it gives off much less light than the same volume of steel. In the 1800s, theaters used lamps that heated a block of calcium oxide (lime) with a torch. This, by the way, is where the term limelight comes from. They used lime because it has a high melting temperature, so you can heat it to a white glow without the block melting (iron melts at 2,800 degrees F, while lime melts at around 4,600 degrees F). Lime also is a good producer of light.

Gas Lanterns
Gas lanterns are incandescent lights. They burn a fuel like propane, white gas or kerosene to produce heat, and the heat causes the mantles to produce light. The mantles are a ceramic mesh that encase the flame produced by the lantern. Typical mantles look like this:


Mantles start out as silk fabric sacks impregnated with different oxides. The standard for decades has been the Welsbach mantle, which uses a mixture of thorium oxide, cerium oxide and magnesium oxide.

When the mantle is installed, you ignite the silk, which burns away and leaves behind a brittle ceramic shell as shown in the picture. This shell is extremely efficient at producing light because of the chemicals it contains and the large surface area of the mesh. The links on the next page contain a reference to the patent for the latest-technology mantle if you'd like to learn more.

So you can see that gas lanterns are very simple. Just about any heated material will produce light. The lantern burns fuel to produce heat. Gas lanterns happen to use mantles (instead of limestone blocks, for instance) because the mantles are very efficient at producing light from the heat they receive.

For more information on gas lanterns, incandescence and related topics, check out the links on the next page!

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