Neon sign

They are the most common use for neon lighting,[1] which was first demonstrated in a modern form in December 1910 by Georges Claude at the Paris Motor Show.

[3] The installations in Times Square, many originally designed by Douglas Leigh, were famed, and there were nearly 2,000 small shops producing neon signs by 1940.

[4][5] In addition to signage, neon lighting is used frequently by artists and architects,[4][6][7] and (in a modified form) in plasma display panels and televisions.

[8][9] The signage industry has declined in the past several decades, and cities are now concerned with preserving and restoring their antique neon signs.

[13][14] The discovery of neon in 1898 by British scientists William Ramsay and Morris W. Travers included the observation of a brilliant red glow in Geissler tubes.

[15] Travers wrote, "the blaze of crimson light from the tube told its own story and was a sight to dwell upon and never forget.

[14] From December 3–18, 1910, Claude demonstrated two 12-metre (39 ft) long bright red neon tubes at the Paris Motor Show.

[19] Claude's associate, Jacques Fonsèque, realized the possibilities for a business based on signage and advertising.

The next major technological innovation in neon lighting and signs was the development of fluorescent tube coatings.

In place of dumpy little bulbs sputteringly spelling out Café or Theatre, there were long swooping spirals of pure brilliant colour.

A waiter outlined in bright red with a blazing white napkin over his arm flashed on and off over a large Café.

Puget Sound Power and Light Company cut through the rain and darkness, bright blue and cheery.

The greatest number of colors (including all shades of blue, yellow, green, violet, and white, as well as some cooler or softer shades of pink) produced by filling with another inert gas, argon, and a drop of mercury (Hg) which is added to the tube immediately after purification.

Neon lights are exceptionally long-lasting due to their vibrant colors and the ability to craft tubes that function for decades.

Interestingly, smaller diameter tubes produce brighter neon light, but also have higher resistance.

The evacuation is paused, and a high current is forced through the low-pressure air in the tube via the electrodes (in a process known as "bombarding").

The bombarding transformer acts as an adjustable constant current source, and the actual voltage during operation depends on the length and pressure of the tube.

Typically the operator will maintain the pressure as high as the bombarder will allow to ensure maximum power dissipation and heating.

This very high power dissipation in the tube heats the glass walls to a temperature of several hundred degrees Celsius, and any dirt and impurities within are drawn off in the gasified form by the vacuum pump.

The greatest impurities that are driven off this way are the gases that coat the inside wall of the tubing by adsorption, mainly oxygen, carbon dioxide, and especially water vapor.

The cathodes are prefabricated hollow metal shells with a small opening (sometimes a ceramic donut aperture) which contains in the interior surface of the shell a light dusting of a cold cathode low work function powder (usually a powder ceramic molar eutectic point mixture including BaCO2), combined with other alkaline earth oxides, which reduces to BaO2 when heated to about 500 degrees F, and reduces the work function of the electrode for cathodic emission.

Once these gases and impurities are liberated under pre-filling bombardment into the tube interior they are quickly evacuated by the pump.

While still attached to the manifold, the tube is allowed to cool while pumping down to the lowest pressure the system can achieve.

Neon or argon are the most common gases used; krypton, xenon, and helium are used by artists for special purposes but are not used alone in normal signs.

In most mass-produced low-priced signs today, clear glass tubing is coated with translucent paint to produce colored light.

Over time, elevated temperatures, thermal cycling, or exposure to weather may cause the colored coating to flake off the glass or change its hue.

Light-emitting tubes form colored lines with which a text can be written or a picture drawn, including various decorations, especially in advertising and commercial signage.

By programming sequences of switching parts on and off, there are many possibilities for dynamic light patterns that form animated images.