What Makes Neon Lights Glow?

In 1910, attendees of the Paris Motor Show saw something quite unlike anything they’d seen before: the world’s first neon lamp. Two years later, a Parisian barbershop installed a neon sign that read “Palais Coiffeur,” creating an effect so eye-catching it soon proliferated in Paris and then the rest of the world.

Even the City of Light saw something special in neon, which has a distinctly vibrant color compared to traditional light bulbs. That’s because neon lights are built differently and use different physics to achieve their luminescence. Here’s a look at what makes neon glow.

A Noble Gas

Neon is an element, one of 94 naturally occurring types of atoms found on the periodic table, alongside other elements such as oxygen and iron. Specifically, neon is a noble gas. While some elements, such as fluorine, are highly reactive, noble gases are mostly unreactive, or inert, because they have a completely full outer electron shell.

Unlike a traditional light bulb, neon lights contain no filament — the thin wire that’s heated to produce light. They consist of a glass tube, with an electrode on either side that contains a small amount of neon gas sealed inside. 

When an electric voltage is applied, some of the neon atoms lose an outer, negatively charged electron and become positively charged ions. The term for ionized gas made of positively charged ions and free electrons is plasma. Much like magnets, opposites attract: The positive ions are drawn to the negative terminal, while the electrons are attracted to the positive terminal.

As these particles bounce around inside the tube, they collide, transferring energy between them. An electron becomes “excited” when it absorbs extra energy. To return to its normal state, an excited electron releases energy, often in the form of light or heat. 

In the case of a neon sign, it’s both — it emits a reddish-orange glow that we nostalgically associate with such signs. Since they also give off heat, neon signs are slightly warm to the touch when turned on. The buzzing sound associated with neon signs doesn’t come from the gas, but from the electricity needed to excite it in the first place.

Not All Neon Lights Are Neon

Despite the use of “neon” as a catch-all term for glowing signs using this form of illumination, not every sign actually contains neon gas. Other noble gases can be used since they have similar atomic structures.

Neon’s light is a reddish-orange hue, but other noble gases produce different colors. Xenon’s light is a pale blue. Helium’s is a pinkish yellow. Gases can be combined to create new colors, or a signmaker might coat the glass tubes with a phosphor or other chemical that will glow a particular color when energized. 

However, many modern “neon” signs don’t contain any gas at all, neon or otherwise. Instead, they’re just colored LEDs — the same types of bulbs many homes now use in lamps and fixtures (and TVs).

Such signs are easier to make, as glass tubes must be heated and bent into shape by hand whereas LEDs typically use silicone or PVC tubing instead. They’re also more durable, programmable, and cheaper, adding a pop of color to a business or home for a fraction of what it would cost to buy and power a neon sign.

That doesn’t mean classic neon signs are fading away, though. Neon enthusiasts work hard to preserve remaining signs, displaying them in museums like the Museum of Neon Art in Glendale, California, or the Neon Museum in Las Vegas, Nevada.

Organizations such as the National Trust for Historic Preservation provide grants to restore vintage signs and keep them in public view. That way, neon can still excite us, just as — to create its nostalgic glow — we excite it.