The science of neon gas is a surprisingly simple one: the gas neon was discovered in 1898 by William Ramsay and Morris Travers when they isolated it in their atomic spectometer. They immediately discovered the red-orange colour neons shines in when charged electrically and gave it the ancient Greek name for ‘new’: neon. From then on the history of neon developed very quickly: by 1902 neon gas was being sold in industrial quantities and by 1912 neon signs started appearing as eye-catching advertising signs in Paris.
How do neon lights work?
Neon belongs to the noble gases, together with helium, argon, krypton, xenon and radon. Together they make up Group 18 of the periodic table. The noble gases are known for their property of being highly unreactive: this is because they all have full outer shell of electrons, they are therefore are completely stable.
This means that neon is colorless, odorless and inert at room temperature, it is therefore also not dangerous. It is present naturally in the air you breathe and even in the exosphere of the moon. As soon as you isolate it in higher density (this is where the glass tube comes in) and apply moderate electric voltage to it, it becomes reactive and glows.
Neon lights are therefore composed of a sealed glass tube containing a small quantity of neon gas. At each end of the tube there is an electrode, which allows the tube to be connected to an electric power source and to create an electric circuit. Once electric voltage is applied to the neon atoms, the energy removes one electron from the atom’s outer shell - having lost one electrode at this point the neon atoms are positively charged and are attracted to the negative terminal, while the single electrons are attracted to the positive terminal.
This movement of atoms and electrodes is what causes the light to be produced: as atoms hit each other and electrodes release energy in the form of a photon, light and heat are produced.
The electrodes of each noble gas release a specific and characteristic wavelength of photons, which determines the colour the gas will shine in - neon for example glows red/orange.
The colour of neon is strictly orange-red, in its pure form and in a transparent glass tube it makes the colour classic red. All neon signs that are not in classic red, do not actually contain the gas neon. Each of the noble gasses glows in its own colour when exposed to high voltage; for example helium becomes pink, krypton glows yellow/green, xenon shines in lavender blue and argon in light blue. Radon is the only noble gas that does not react to electricity by lighting up in colour, and is thus the only noble gas that is never used in neon signs. Today however, all colours except classic red actually contain argon. This is because argon is the gas that requires the least amount of electrical input to react and thus uses the least energy of all.
The broader spectrum of neon lights colours is achieved by using different kinds of coating for the glass employed for the tubes: that is why neon tubes are mostly white when turned off, or sometimes tinted. So, while classic red and classic blue are made of transparent glass and respectively neon and argon glass, all other colours are achieved by manipulating the glass either with fluorescent powders (such as for pink, purple or green neons) or by actually colouring the glass (for orange, cobalt blue and ruby red), rather than the gas.
The required electrical input for neon signs, i.e. your typical ‘open’ sign, is about 90 watts, which actually makes it more efficient in terms of energy consumption than a fluorescent light bulb. In addition neon lights generally last for about 10 years, after which they simply need to be refilled with gas.
Interestingly, alternative uses of neon are vacuum tubes, light meter tubes, television tubes and others, though its most interesting and tubeless use would probably have to be cryonics: the freezing of corpses for preservation, trusting that in the future we will have developed the necessary medical technology to re-enliven them. In film and art, neon has continuously been associated with futurism for the past 100 years - we guess you could say neon is one of those cases in which the science of neon actually turns out to provide the proof for a seemingly unfounded cultural perception.