Answers to a few commonly asked questions about neon (Copyright © 1995 by Ray Koltys):
How do neon tubes light?A tube of glass is sealed tight with electrodes at each end and a small amount of neon (or other inert gas) inside. An electric arc is struck through the tube with transformer that produces a very small amount of current at a very high voltage. The arc excites the gas molecules, causing them to emit light. For you techies, neon is typically lit with 15 to 60 milliamps at 2 to 15,000 volts, depending on the footage being lit.
How are neon tubes made?Glass tubes, sold in four foot lengths, are bent to match a pattern by heating sections of the glass with a specially configured natural gas torch. Once the glass is in the desired shape, electrodes are welded to each end. One of the electrodes has a small tube sticking out one end, which is hooked up to a manifold with stopcocks for gas bottles, and a vacuum pump. Simultaneously the electrodes are hooked up to a large transformer. Most of the air is pumped out of the tube, and an electric arc is struck through what is left. This arc has a lot of current and heats the air up, which in turn heats the tube and cooks the impurities out of the glass so they can be sucked out by the vacuum pump. The tube is brought to the smoldering point of paper (Farenheit 451) and then allowed to cool while the tube is pumped down to a total vacuum. A small amount of neon or other gas is let in, the tube is sealed off, and it is ready to light. This entire process is known as bombarding. For the techies again, the tube is bombed with 3 to 5 amps at 12 to 15,000 volts.
How do you get the colors?There are a few ways to get different colors with neon. The most basic is by using a different gas. Using clear glass tubes there are two colors that are practical: neon gives you a bright red-orange, while argon gas combined with mercury vapor gives you a pale blue. Straight argon (without the mercury vapor) creates a faint purple and krypton emits a ghostly white, but neither of these is bright enough for commercial use.
Colors can also be created by coating the inside of the glass tubes with phosphors. Ultraviolet light emited by the mercury in the argon/mercury combination causes the phosphors to glow, similar to flourescent lights. Phosphor coated tubes are sold in a wide range of colors ranging from purple to green, as well as warm and cool whites.
When a more saturated color is called for, there are also tubes that are made with colored glass. Names like Bromo Blue and Ruby Red accurately describe the richness of the color emitted by these tubes, but this glass is more difficult to make and is sold at a premium price.
Are neon signs dangerous?Neon signs operate at a high voltage, but with very low current. The zap you would feel if you accidentally were shocked is a surprise, but not dangerous. As Billy Crystal said in Running Scared, "It's not the volts that gets you. It's the amps." Improperly wired signs can start a fire, but the risk is about the same as with any improperly wired electrical device.
When were neon signs invented?Neon sign technology was first successfully demonstrated in France in 1910 by Georges Claude. His first patent was granted in 1915, and by 1930 there was a booming neon sign industry.
Where can I learn more?The definitive volume on the subject is "Neon Techniques & Handling," Copyright © 1977 by Signs of the Times Publishing Co (ST Publications). They can be reached at 407 Gilbert Ave, Cincinnati, OH 45202, Ph: 513-421-2050.
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