Neon signs are a distinctive form of illumination, classified as a cold cathode gas-discharge lamp. This technology creates light by passing electricity through a low-pressure gas sealed within a glass tube. The visual appeal of these luminous, custom-bent tubes has made them a cultural fixture in advertising and art since their commercial introduction by French engineer Georges Claude in the early 1900s.
The Core Structure and Components
The physical foundation of a traditional neon sign is its glass tubing, which is typically made from soft lead glass or a type of soda-lime glass. This specialized material is heated by hand using a torch, which allows a skilled artisan to bend the tubes into letters and intricate shapes. The standard diameter of this tubing ranges approximately from 8 to 15 millimeters.
Metal electrodes, usually constructed from iron or nickel, are sealed at both ends of the glass tube to introduce the electrical current into the enclosed gas. Before the illuminating gas is introduced, the tube must be processed using a vacuum pump to remove all air and impurities. This ensures that only the intended low-pressure inert gas remains inside to react consistently with the electricity.
The Illuminating Elements (Gases and Phosphors)
The iconic color of the light is determined by the specific gas sealed inside the tube. Pure neon gas, which gives the signs their name, produces a bright, unmistakable red-orange light when electrified. To achieve other colors, artisans rely on argon gas, which naturally emits a blue or lavender light.
Argon-filled tubes require the addition of a trace amount of mercury vapor to operate efficiently. When the argon is ionized, the mercury vaporizes and helps stabilize the electrical discharge, creating a more uniform glow. This combination produces a strong blue light, and the mercury vapor also emits ultraviolet (UV) light.
To unlock a full spectrum of colors beyond the basic red and blue, the inside of the glass tubing is coated with various phosphor powders. The invisible UV light generated by the argon-mercury mixture excites these coatings, causing them to fluoresce a visible color. Different phosphor chemical compositions allow for the production of colors like greens, yellows, and whites, all originating from the argon-mercury core.
The Power Source Requirements
Traditional neon signs are cold cathode devices that require a high voltage to initiate the electrical discharge. This ionization process demands a voltage that typically ranges from 5,000 to 15,000 volts, depending on the length and diameter of the glass tubing. This high potential is supplied by a step-up transformer or a modern power supply, which boosts the standard household voltage to the high-kilovolt range.
The connection between the transformer and the electrodes is made with specialized high-voltage insulated wire known as GTO cable. This cable features a stranded bare copper conductor and is encased in thick, durable insulation, often made from Thermoplastic Elastomer (TPE) or silicone. The GTO cable is designed to safely handle the high voltage and maintain a secure connection, preventing electrical discharge outside the glass tube.
Modern LED “Neon” Composition
An increasingly popular alternative to the traditional glass tube is the modern LED “neon” sign. These signs use solid-state light-emitting diodes (LEDs) as their light source, arranged in a flexible strip that operates on a much lower voltage. The LED strips are encased in a flexible polymer material, most commonly silicone or Polyvinyl Chloride (PVC) tubing.
This opaque or translucent tubing acts as a light diffuser, scattering the bright points of light from the individual LEDs to create the continuous, uniform glow characteristic of classic neon. These signs operate using a low-voltage DC power adapter, converting household AC current into the 12 or 24 volts required by the LEDs.