A neon sign, simply stated, is a lighting display made of glass tubes. These tubes are filled with gas and bent into the shape of artistic letters or decorative designs. When heavy voltage electrical current is passed through the captured gas, the tubes emit light and the sparkling illumination arrests the attention of all people passing in that area.
Although neon gas was originally used in neon signs, it is now only used only to produce red and orange colors. Argon, or an argon-neon mixture, is today widely used in making neon signs. A small quantum of mercury is added to the argon to produce an intense blue light. These gases, along with varying tints along with phosphor coatings for the glass tubes produce whole range radiant colors.
Tubes of optical tints in various colors are used or clear glass is chosen if a strong blue light is desired. Xenon, krypton, and helium gases are used selectively for creating fascinating color effects.
The glass tubing used in manufacture of neon signs is made from soft lead glass that can be effortlessly bent and formed into any desired shape. The electrodes at either end of a section of illuminated tubing are made from virgin iron encircled by a cylindrical glass jacket with one end open. A wire is than fixed to the metal electrode and it passes through the closed end of the glass envelope. The closed end is sealed into the end of the sign tubing and the open end protrudes into the tube.
The high-voltage electricity required to power the sign is obtained through a transformer which converts the 120 volts to as high as 15,000 volts for the sign. The transformers are connected to the electrodes in the sign by means of special wire – known as GTO wire – that is insulated for up to 7,500 volts.
The sign tubing is supported in different ways depending on its size and application. Small indoor signs have a thin steel skeleton framework that supports both the tubing and the power transformer. Large outdoor signs are supported by wood, steel, or aluminum structures. The transformer is placed inside a cabinet to protect it from the weather.
The following are the sequential steps involved in the manufacturing of neon signs:
* Designing – Each neon sign is unique and must be designed to create the desired display within the confines of the available space.
* Prepare the tubing – Lengths of glass tubing are cleaned and placed vertically in a coating machine. The coating machine blows a liquid phosphor suspension upwards into the tube and then allows it to drain. The tubes are placed vertically in an oven which dries the coating.
* Bend the tubing – The glass tubing is heated and softened using a variety of burners. To prevent the softened tubing from collapsing, the tube bender attaches a short length of flexible hose to one end. While the glass is still soft, the operator gently blows into the hose to force the tubing back to its original diameter.
* Bombard the tubing – Bombarding is necessary to remove any impurities from the glass, phosphors, and electrodes that are used. First the air inside the tubing is ejected. After the vacuum reaches a certain level, dry air is allowed back into the tubing until the desired pressure is attained. A very high-current transformer is connected to the electrodes. The high current heats the glass and the metal electrode. This heating forces the impurities out of the materials, and the vacuum pump carries the impurities out of the system.
* Filling the tube – Once the tube has cooled, the gas is inserted under low pressure. The gas must be free from impurities in order for the sign to operate properly and have a long life… The tube port is then heated and sealed off.
* Aging the tube – The finished gas-filled tubing is put through an aging process. The purpose is to allow the gas in the tube to stabilize and operate properly. After the successful aging process, the neon sign is ready for installation.