Neon gas A radiant science

The science of Neon gas is a surprisingly simple one: Neon gas was discovered in 1898 by William Ramsay and Morris Travers when they isolated it in their atomic spectrometer. They immediately discovered that the red-orange Neon gas begins to glow when electrically charged and gave it the ancient Greek name for "new": Neon. From then on, the history of Neon developed very quickly: from 1902 onwards, Neon gas was sold in industrial quantities, and from 1912 onwards, Neon signs appeared in Paris as eye-catching billboards.

A red neon tube switched on in close-up

How does Neon gas work?

Neon is one of the noble gases, along with helium, argon, krypton, xenon and radon. Together they form group 18 of the periodic table. The noble gases are known for being very non-reactive: they all have a full outer shell of electrons and are therefore completely stable.

This means that Neon gas is colourless, odourless and inert at room temperature, so it is also not dangerous. Neon gas is even naturally present in small quantities in the air we breathe, and even in the exosphere of the moon. As soon as you isolate it at a higher density (this is where the glass tube comes in) and apply a moderate electrical voltage to it, it becomes reactive and glows.

A yellow and red neon tube switched on in close-up

Let there be light This is what Neon gas looks like!

So Neon tubes consist of a sealed glass tube that contains a small amount of Neon gas. At each end of the tube is an electrode that allows the tube to be connected to an electrical power source and form a circuit. Once an electrical voltage is applied to the Neon atoms, the energy removes an electron from the outer shell of the atom. After losing an electrode at this point, the Neon atoms are positively charged and are attracted to the negative pole, while the individual electrons are attracted to the positive pole. It is through this movement of atoms and electrodes that light is produced. When atoms meet and electrodes emit energy in the form of a photon, light and heat are produced.

A neon tube in an abstract form

Is every fluorescent tube filled with Neon gas?

The electrodes of each noble gas emit a specific and characteristic wavelength of photons that determines the colour in which the gas will glow - Neon, for example, glows red/orange. In a transparent glass tube, it makes the colour classic red. All Neon signs that are not classic red commonly contain a mixture of Neon & Argon gas. Each of the noble gases glows its own colour under high voltage; e.g. helium turns pink, krypton glows yellow / green, xenon glows lavender blue and argon light blue. Radon is the only noble gas that does not react to electricity by glowing in colour, and is thus the only noble gas never used in Neon signs. Today, however, all colours except the classic red actually contain argon. This is because argon is the gas that requires the least amount of electrical energy to react, and therefore consumes the least energy.

A red neon tube in the datail view

The wide colour spectrum of Neon tubes is achieved by using different coatings. This is why Neon tubes are usually white or sometimes tinted when switched off. So while classic red and classic blue are made of transparent glass or Neon and argon glass, all other colours are achieved by manipulating the glass with either fluorescent powders (as in pink, violet or green Neon tubes) or by actually colouring the glass (in orange, cobalt blue and ruby red tubes) rather than the gas.

The electrical power required for Neon signs, i.e. your typical "open" sign, is around 90 watts, which actually makes the energy consumption more efficient compared to a fluorescent lamp. In addition, Neon tubes usually last about 10 years.

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