(Editor’s note: the following article is excerpted from The Neon Engineers Notebook, Second Edition, available from Lightwriters.com.)
With the plethora of neon colors that are now available it is hard to believe that at its beginning neon had an extremely limited palette. Emerging in the late 19th century, neon was very much born out of experimentation and the recent discoveries of inert gases such as argon and neon. When neon signage got a foothold in America in the early 20th century, the popularity and therefore demand pushed the industry to find ways of making it better. It was this experimental mentality that gave neon its first baby steps and in time gave it its wings to soar.
There are four ways to generate color in luminous tubes. The first and most fundamental is the use of inert gas. The most common of these used in neon applications are neon and argon. Krypton and xenon can also be used, and even helium will light a tube (although helium is rarely used in neon production). One of these gases is pumped into a vacuum-tight tube fitted with two electrodes and when connected to an electrical source, the gas will glow.
The second method is using colored glass tubing. Glass can be colored by adding various elements into the original glass mixture. It is possible to directly add fluorescent materials, like uranium, into the glass mixture. This was done in the early 1930s, before the advent of phosphor, in the United States and Germany. The Germans made theirs in two layers: There was a fluorescent layer on the inside which was encased by a clear layer on the outside. Neither of these methods gained acceptance because the fluorescent brilliance was not much better than that of standard clear or colored tubes for the hassle it was to bend. Other elements such as cobalt are added to glass to make “bromo blue” called such for its resemblance of Bromo-seltzer bottles. This method of adding other elements into the glass itself made the glass brittle and also had such a high strain on the glass it broke often. To work this glass took more time and a higher level of skill.
The third method of achieving color is coating the inside of a glass tube with a phosphor. When mercury in a tube becomes excited by electricity, it emits an ultra-violet light, which in turn causes the phosphor to fluoresce. There have been many advances of this practice in the last several decades, and now with the introduction of tri-phosphors, the spectrum of colors that can be achieved in neon has skyrocketed.
Finally, one can achieve any desired color through applying a paint-like coating to the outside of the tube. This can become problematic if a repair needs to be done because the paint will have to be stripped in order for a repair to be made.
IN THE BEGINNING…
There was light. Bright red and soft blue light to be specific. These were originally the two main colors available using clear glass in neon sign making. Sir William Ramsay discovered argon, and along with his associates also discovered neon, krypton, xenon and helium during the period of 1884-1898. It was then noticed that when excited by electricity these gases will glow: a tube containing neon at a low pressure will emit a bright reddish-orange light; when argon is placed by itself in a tube it will emit a soft purple. When a tiny drop of mercury is added to argon a bright sky blue is emitted due to the electrification of mercury vapor. Krypton emits a very soft white with a lavender tinge; xenon emits a ghostly white; and helium emits a yellow gold.
Of course it was of interest to find a practical application for these glowing gases. It was already known that mercury inside of a vessel when shaken vigorously would luminesce. It then became understood that these luminous gases could be used to “support” the mercury in a tube. Georges Claude used this information in conjunction with his invention of the neon electrode and shocked the world in 1910 by displaying the first ever neon tubes. It was only a short time before the first neon sign was sold that it quickly found its way over to America.
The instant that neon signage hit America it was an aesthetic that defined our nation. Within a very short period around 15 tubing colors were being made (hand-drawn) at Corning Glass Works’ Fallbrook plant. It was the popularity and demand that propelled neon sign makers to look for ways of achieving different colors.
It didn’t take long before in the late 1930s fluorescents were first used in conjunction with neon to produce a new array of colors. With each advent of a new phosphor, two new colors were being produced. A phosphor-coated tube filled with mercury and argon will produce a different color than a tube filled with neon. The development of phosphors is still ongoing today, with huge improvements. White was the first phosphor color achieved in neon and green followed shortly thereafter.
In the 1940s the availability of phosphor-coated tubes started to open up. “Old school” materials for neon often contained poisonous ingredients such as arsenic, beryllium and cadmium. This led to the introduction of the calcium halophosphate family of phosphors that are non-toxic, together with advances in blue and green emitters which expanded the industry’s color spectrum, namely making available a large range of whites which are still being used today.
Soon after the introduction of white and green, blue and pink phosphors were made available. This opened the neon world up to some exciting advances in color options. Different gases with a certain phosphor could create various colors, and phosphors could even be put in colored glass adding to the possibilities. However, after World War 2 Corning started to limit the production of its colored tubing to colors suited for machine production, namely ruby red, blue, and noviol.
The new availability of phosphor coatings played a major role in the huge neon boom of the 1950s and early 60s. With the country putting a large effort into research about phosphors for use in television sets, it was realized that this research and its findings could be applied to the neon industry. The first color television came out on the market in 1954 using similar color technology as neon. In fact the phosphor yttrium vanadate is used in a vast amount of televisions and computer monitors and to this day is still what the neon industry uses for “coral pink”.
Turquoise came out on the market around the same time and when used in conjunction with pink tubes, the diner era came to be defined. These two colors were wildly popular in the fashion of the time and soon every diner and drive-in theater had to have neon as part of their display. This popularity encouraged neon research to find still more ways of increasing the color spectrum.
THE NEON DEPRESSION
Despite the popularity of neon signage in the 1950s, neon made a sharp decline in the late 60s and 70s due to a new popularity of plastic signage, making neon seem “old-fashioned”. This was crippling to the neon community, where in the 70s there were as few as 300 tube benders in America. Because of this lack of demand and large expense, Corning Glass Works ceased its production of colored glass tubing. Eventually the original high quality American-made colored glasses such as ruby, emerald, bromo, and noviol faded out of the picture. It seemed as though neon was a dying art.
In the early 80s double-coated phosphors tubes were developed to make up for the deep rich color that was lost when American-made colored tubing was discontinued. This dramatically boosted the colors available to close to 100. The aesthetic of the 80s cried out for the new colors of pastel neon and it started to make its comeback. Artists like Rudi Stern largely helped the neon revival and advocated the use of this growing technology.
Around this same time Italian-made colored soft glass tubing started to be accepted into the American neon industry. This somewhat replaced the void of the old colored glass tubing produced by Corning GlassWorks, however some colors have never quite reached the deep beautiful colors produced by the originals.
The availability of neon color choices took a giant leap in the early 1990s when rare-earth phosphors, or tri-phosphors, started to be used in the neon industry. These tri-phosphors emit a narrow wavelength band from the color spectrum, giving deeper and more saturated colors. They have also dramatically increased the range of whites and the quality of appearance of whites that can be achieved. These tri-phosphors had been developed in the 60s for use in other industries, mainly television, but were also adopted in the 70s and 80s by the lighting industry for use in fluorescent lamps.
The neon industry resisted the use of tri-phosphors up until the 90s because of the seemingly high cost. Tri-phosphor coating can cost twice as much as standard tubing; however, the benefits of the tri-phosphors largely outweigh the cost issue. The narrow wavelength bands emitted by tri-phosphors make it possible for more available light to be transmitted, increasing the lumen per foot output, making these signs more vibrant and much more efficient.
KEEP ON KEEPIN’ ON
The development and use of the rare-earth phosphors for neon has brought us to where we are today in the early 21st century. Neon has seen extremely prosperous and trying times, but hopefully will continue to gain momentum as the years go on. Currently the industry is continuing to grow and has made a stunning comeback from the lull of the 70s. The availability of colors for neon is now over 150, but its rise and fall through the years can be directly correlated to the demand presented. So as long as the demand is present the spectrum for neon can only continue to grow.
Timeline of Neon Colors
1675 First luminous tube: Mercury glows when shaken
1744 Sir Georges Stokes discovers phosphor
1894-98 Raleigh & associates discover inert gases
1910 Georges Claude shows first neon tubes
1912 First neon sign sold in America
1930s Colors available with catalog numbers from Corning Glass Works (CGW) 1935:
Soft canary (uranium)—333 or 372
Amber, medium soft—335
Soft signal green—440
Soft dark purple—552
1939 Phosphors are introduced into the neon industry
1940s An array of halophosphate whites available
1945 Colored glass tubing is now limited to Ruby, Blue, and Noviol
1950s Turquoise is introduced and the neon industry booms
1960s More than 24 colors available
1970s Neon recession. CGW stops making colored glass tubing
1980s Double-coated phosphor tubes developed. The color options increase dramatically to nearly 100. The FMS Corporation produced a fair amount of double-coated colors in the early 1980s. Some easily gained popularity and are still in use today, such as Bright Yellow, Clear Gold, Veep Green, Neo Blue, Neo Red, Vine Green, and Deep Aqua. Others such as Topaz, Frog Green, Lilac, Dusty Rose, Aqua, Blue Sky and Dusty Blue failed to gain acceptance and phased out of production by the late 80s.
1990s Rare-earth phosphor (triphosphors) are used for neon. Italian-made colored glass tubing gains acceptance in the U.S. The colors available jumps to over 150!
Early 21st Century Rare-earth phosphors continue to be developed to continually increase product value