Neon

A neon sign is a very simple device. It consists of a vacuum-tight glass tube, fitted at each end with an electrode. Inside the tube is a small amount of rare gas. Connected to the two electrodes is a source of high-voltage electrical power. When the current is turned on, the tube glows with a steady piercing light. The rare gases, neon, argon, helium, xenon and krypton, are ideally suited for use in signs. The two most common gases used in neon signs are neon and argon. While neon is very bright, argon's light is weak due to its low resistance. Neon gas gives off a red glow. This gas is normally contained in tubing that is clear in color, and when illuminated, projects the brightest red color. Almost everything else is filled with argon gas. When you see yellow, blue, green, white or any of several other shades, these tubes are filled with argon gas.