The neon sign has served as a beacon for businesses, restaurants and entertainment venues for over 100 years. Sleek, elegant, colorful, and playful they attract the eye in ways that no other signs can. So how do these signs that blend science, light and artwork and from what are they made?
How is Colored Light Produced in a Neon Sign?
At their simplest, neon signs require three elements; a vacuum tube, an electrode, and any one of a number of the noble gases inside the tube that glow when excited by electricity. Noble gases are inert, meaning that they do not readily combine with other elements.
The main gases used include argon, helium, krypton, xenon, and of course neon. It must be noted that all neon signs do not use the element neon. Neon is expensive to produce, and such is not readily used. When excited it glows a bright red, thereby limiting its use to specific color situations. The term “neon” is used as a catchall term in the same way that people call all tissues Kleenex.
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The various noble gases give off the following colors when excited in a vacuum:
- Argon, while inexpensive to produce, gives off a very weak light. It is generally supported by a small additive of mercury to give off a bluish-white resonance. This color can be brightened or altered when used in conjunction with a vacuum tube with an ultraviolet sensitive coating.
- Helium is used in applications where a pinkish to orange-red is desired.
- Krypton emits a warm yellow light. Like argon, its color can be changed to grey or green by applying different coatings to the vacuum tube.
- Excited xenon gases produce a lavender light in its natural state. When used in a neon sign, vacuum tube coatings are used to change the lavender color to various shades of purple.
- Radon, which is a noble gas, is not used in neon signs as it is a dangerous radioactive gas. As such it is not a commercially used product.
While these are the most common gases and colors produced, there are nearly 50 colors that are used in neon sign applications.
The Art of Tube Making and Bending
The process of manufacturing a vacuum tube to be used in neon signage is an extremely technical process that requires a high level of technic to produce a quality tube. Glass tubing must be blown, pulled and bent into the proper shape. It is then meticulously cleaned and then bombarded with hot, dry air to draw out impurities and imperfections. It is then filled with gas and mounted into the neon sign framework.