Once it is trapped in a tube, neon becomes invisible and dull. Then it can be zapped by electricity. Neon literally pulled from thin air and became the brightest light in the modern world. It is a symbol of progress and an integral part of the electronic age.
Philip Marlowe was the hard-boiled detective hero in Raymond Chandler’s detective novels. He was correct about neon. The lights that lit up the night sky in more than a thousand cities had been invented out of nothing. The air itself was the source of the colorful words and images. These mysterious gases were extracted from the atmosphere and placed in glass tubes and then zapped by electric current to produce luminous reactions. Lights fueled by neon and other noble gases were icons for commerce and entertainment in the 20th century. They illuminated the modern age. Early computers and calculators used small neon tubes to create circuits and display circuits. Many of the elaborate neon signs are no longer in use. However, these tubes with the gas-filled inside still shine brightly on a smaller scale and are treasured for their unique light.
Aristocrats of the Air
Sir William Ramsay, a Scottish chemist, began the story of neon in the 1890s. Ramsay is best known for discovering four noble gases (neon argon krypton and xenon) and also identifying and characterizing helium, radon, and other noble gases. He was awarded the Nobel Prize. These six elements form a family distinguished by their inability to bond with other molecules. These noble gases were named for their “nobility”, their insolence.
It took a while before the atmosphere lost all its secrets. The mystery gas was discovered by Henry Cavendish, a prominent chemist, in 1785. They began to attack air using brute-force methods, including reaction, combustion, and absorption, in 1894. This was to remove every atom of oxygen and nitrogen from the atmosphere. Red-hot copper was used to removing oxygen from the air in an early experiment. The deoxygenated oxygen was then passed through red-hot magnesium and soda lime. Copper oxide, copper oxide, phosphoric anhydride, and finally, nitrogen were removed. The remaining oxygen and nitrogen were removed by further steps. They named the residual gas argon (derived in part from the Greek word for “the inactive, lazy one”)
Although argon is less than 1% in the atmosphere, Ramsay believed that other rare gases were hidden in the atmosphere. These elements were discovered by Ramsay and Morris W. Travers in the summer of 1898. They began with purified argon that had been liquefied at low temperatures. Then they added heat to separate gases that could be boiled at temperatures above and below the boiling point of argon. They discovered neon, krypton, and xenon.
These rare gases may not be visible to the naked eye but glow with brilliant colors when they are sealed in glass tubes and energized by high voltage. This gas-discharge tube was named after the electric discharge that caused them to light up. They would be the basis of neon lamps. Ramsay was particularly struck by neon’s bright light. He described the neon spectrum in his 1904 Nobel Prize lecture as “a brilliant flame-colored, multicolored light consisting of many red and orange lines.”
Exploiting the Air
Liquid air, especially oxygen, was first used in theater lighting and industrial welding in the late 19th century. The Joule-Thomson Effect is the basis of all liquefying gas techniques. This effect can be seen in your home or office whenever you use pressurized air to dust a keyboard. As the air expands through a nozzle, it drops the temperature, and condensation forms on the can. Ramsay was trying to isolate his gases when the first practical methods for liquefying air on a large scale appeared. He made sure to mention William Hampson in his Nobel Prize lecture.
Like Hampson, Carl von Linde, and many others in England and Germany, Georges Claude, a Parisian engineer, and inventor, used the Joule–Thomson effect on liquefying water. This allowed for huge amounts of production (up to 10,000 cubic meters per day). Paul Delorme, his former schoolmate, was also his co-founder of L’Air Liquide in 1902. It grew quickly to become a multinational company. Claude also conducted scientific research while selling liquid oxygen for industrial uses. He had initially hoped to find more noble gases by analyzing large volumes of liquefied oxygen, but he was forced into admitting that after Ramsay, there was no further work. His next project combined leftover neon from his air liquefaction with his disapproval of the excessive brightness of electrical lighting.
Lines of Light
Gas tubes were not just used by Claude to provide light. Inventions were inspired by Thomas Edison’s commercial success with incandescent lightbulbs. Daniel McFarlan Moore was an Edison employee who filled 10-foot glass tubes under low pressure with carbon dioxide or nitrogen and added electrodes at the ends. These “Moore lamps”, which lit brightly when electrified, were much more efficient than the incandescent carbon-filament bulbs. Although the lamps were useful for general lighting in shops and offices, they were costly to install (a glass plumber had to connect them on-site), required high-voltage electricity, and were prone to leaking. His company was bankrupted in 1910 when better incandescent lamps using tungsten filaments replaced Moore’s tubes.
Claude quickly discovered that Moore’s idea of neon was more than switching gases. His tubes produced a brilliant glow but the impurities that were released from the hot electrodes quickly dimmed it. The problem of metallic buildup around electrodes caused the tubes to flicker too quickly, but a carbon filter fixed that. Claude used larger electrodes to keep the tubes cooler. The tubes burned brightly and consistently for as many as 1,200 hours.
Claude was finally successful and filed his first patent in 1910 for neon lighting. He demonstrated his invention in December at the Salon de l’Automobile, Paris Motor Show. The exhibition building was filled with thousands of incandescent lamps that glowed off the shiny metal cars below. Two neon tubes measuring 40 feet glowed bright orange-red outside, on the colonnade. Modern technology was displayed: The newest cars and lighting, made possible by Paris’s rapidly expanding electrical network.
Although red neon is not the best for general lighting, Claude insisted that neon could be used in certain situations. This included illuminating monuments or advertising where neon was “the most dazzling and appealing of lights, the better it is.” In a Parisian barbershop, on the Boulevard Montmartre, Claude placed the first-ever neon advertising sign. Soon, a large sign on the roof for Cinzano, an Italian vermouth manufacturer, was installed. Illumination for the entrance to the Paris Opera soon followed. To make the most of his invention, Claude founded Claude Neon to sell neon signage franchises. Although the franchises were expensive ($100,000 plus royalties), there were many openings around the globe, particularly in major American cities. The neon sign was quickly becoming a household brand. Although the first neon signs were simple, animation and a variety of colors would follow later. Business owners competed to trace their signatures onto buildings and rooftops. Claude’s sign monopoly lasted into the 1920s and was eventually broken by former employees who leaked his trade secrets.