Neon lights are incredibly bright, colorful, and reliable. You often see them on displays, signs, and even on airport landing strips. But have you ever wondered how neon lights are made, how they work, and how they produce different colors?
How Neon Lights Work
A neon light is made up of a glass tube that’s filled with a small amount of neon gas in low pressure. The main reason why neon is used is that it’s one of the noble gases, which are typically inert. This means that each atom of these gases has a filled electron shell, such that the atoms don’t react with other atoms, and that it takes a lot of energy to dislodge an electron.
At either ends of the tube is an electrode, where alternating current (AC) or direct current (DC) is run. If a DC current is used, the glow on the light is seen around a single electrode. Most neon lights you see use AC current.
When a current passes through the terminals, there’s enough energy to remove an outer electron from the neon atoms. In case the voltage is not sufficient, the kinetic energy won’t be sufficient to allow the electrons to escape their shell in the atoms, and no light will be produced. The free electrons are usually attracted towards the positive terminal, and the cations (positively charged neon atoms) are attracted towards the negative terminal. The charged particles are known as plasma, and they ideally complete the electric circuit of the lamp.
But where does the light come from? Well, the atoms move around in the tube while hitting each other. Through this, they transfer energy to each other, and a lot of heat is produced in the process. As more electrons escape their atoms, the others gain more energy and become ‘excited’, putting them in a higher energy state. To return to its original state, the electron has to lose this gained energy in form of a photon (light).
The color of light produced is dependent on how much energy the excited electron had to lose to return to its original state. The energy is set at intervals, such that each interval releases a characteristic photon wavelength. As such, each excited atom of the noble gases will release a characteristic color of light. Neon produces a reddish-orange color.
How Different Colors are Produced
Aside from the reddish-orange color of neon, there are two main ways of producing other colors. One way is using another gas or a mixture of gases in the tube to produce colors. That’s because each noble gas produces its unique color of light. For instance, krypton glow green, helium pink, and argon blue. When these gases are mixed, it’s possible to produce intermediate colors.
The second way of producing colors is coating the glass tubing with chemicals such as phosphor, which glow at a given color when energized. Since there’s a wide range of coatings available, most modern lights don’t use neon any more, but are fluorescent lamps that use a phosphor coating and an argon/mercury discharge. So, if you notice a clear light glowing in a color, that’s light from a noble gas.
Another way of changing the color of the light produced is controlling the energy supply to the light, though this is not used in light fixtures. Although each element produces its own color of light, the excited electrons can occur at different energy levels, which generally correspond to the light spectrum an element can produce.
How Neon Signs are Made
Now that we know how neon lights work, we can now look at how neon signs are made at https://atlanticsigncompany.com.
- Noble gas: Argon or an argon-neon mixture is commonly used in neon signs. A small amount of mercury may be added to the gas in order to improve the intensity of the light. Xenon, helium, and krypton are also used to produce special color effects.
- Glass tubing: most neon signs use a soft lead glass, which is easy to bend and forge. It can range from 0.3 inches to 1.0 inches in diameter, with a length of 4 to 5 feet.
- Electrodes: these are on each end of the tubing and are made from pure iron enclosed in a cylindrical glass envelope or jacket.
- Transformer: this provides the high-voltage electricity used to power the sign. It converts the 120 volts received from the lines and delivers as much as 15,000 volts to the sign.
- Framework: large outdoor signs are usually supported by steel, wood, or aluminum structures, while small indoor signs are supported by a thin steel framework.
Neon signs are mostly made through a largely manual process, which involves bending the tubing, removing any impurities from the tubing, attaching the electrodes, evacuating the air, and adding the gas. The process typically involves the following:
Preparing the Tubing
First, the glass tubing is cleaned and placed on a coating machine. Liquid phosphor is then blown into the tubing and drained from the other end. Color tints are also applied this way, and the tube is placed vertically to dry the coating.
Bending the Tubing
The sign’s design is laid out on a heat resistant asbestos sheet. The tubing is then heated using a range of different burners to soften it. Ribbon burners are used to shape and curve the glass into the desired letters or curves based on the design. The larger neon signs are usually made of several section of glass tubing. A practical limit for each section is about 8 to 10 feet.
Impurities in the glass, electrodes, and the phosphors are removed through a process known as bombarding. It entails evacuating the air inside the tubing and connecting a very high current transformer to the electrodes. The current heats the glass to about 216°C (420°F) and the metal electrode to 760°C (1400°F). This forces impurities out of the materials, and a vacuum pump is used to carry the impurities out of the system.
Filling the Tube
When the glass tube has cooled, the noble gas is put under low pressure. It must be free from any impurities for it to work properly and be durable.
Aging the Tube
The gas-filled tubing is then taken through the aging process, otherwise known as “burning in the tube”. This is meant to allow the tubing to stabilize and operate properly. In addition, a transformer rated slightly higher than the normal operating current is attached to the electrodes, and any problems like flickering in the gas, or formation of a hot spot in the tube means the tubing has to be opened to repeat the bombarding and filling processes.
Mounting and Installation
For the small neon signs, the tubing is mounted on the framework and wired in the shop. The larger signs are typically mounted in pieces and installed on the building or the support structure where they are wired and interconnected.