It was over 150 years ago that inventors began toying with the idea of creating artificial lighting powered by electricity. The first light bulb is generally associated with Thomas Edison, who patented his first bulb in 1879 and again in 1880. Those patents led the way to the commercialization of the incandescent light bulb. Those first light bulbs were quite rudimentary and lasted a very short time but the idea was part of the beginning of the commercial lighting evolution which has, today, become a lighting revolution with the introduction of LED lighting.
Prior to the 1870’s and the first light bulb, British inventors discovered that electric powered light was possible with the arc lamp. This type of lighting was the first commercially successful and the first widely used form of electric powered light. An arc lamp is a lighting device which can produce high intensity light by creating an arc of electricity across two specially sized and spaced carbon rods. The first recorded experimentation of this concept was carried out by an English chemist, Sir Humphrey Davy, somewhere between 1800 and 1809, according to differing sources. Numerous sorts of rod materials such as steel and other metals had been tried but the carbon rods were found to be the best material. These lights, although bright, were fraught with problems. The most annoying and dangerous issue was the live sparks which were generated and could, and did, easily start fires. These lights were first used in outdoor applications but eventually were actually used in places where people shopped, such as department stores, where sparks were known to randomly fall on the floor, merchandise and patrons. Not the best of shopping experiences. The light emitted also produces UV-A, B and C light, which are harmful to eyes, skin, and some forms of merchandise – at that point in time, UV light was an unknown factor. It was discovered that diffusing the light made for a much better quality of light, both in actual visible light output and affording some help with the fire hazard that went along with the lights. The early diffusing globes had open tops to help the heat escape and were made of opal glass (the heat generated by the arc could be in the vicinity of 6500° F!). The glass provided some help in the sparking predicament, better visible light and, although unknown at the time, also helped decrease the UV output. These early semi-enclosed globe covered arc lights are not to be confused with an enclosed carbon arc light.
An enclosed carbon arc light was eventually developed, these lights used a rod which was fed into an enclosed globe which contained another rod. The lack of oxygen within these globes made the light burn with less intensity but also provided for a longer life and contained the sparks produced by the arcing. The early developers discovered that if mercury was added to the enclosure, that when an arc was struck a bright greenish light was produced. This idea eventually led to the mercury vapor lighting of current times, although the early lights were not very popular, as the green color was considered quite ugly. In a later discovery, it was determined that the UV output of these ugly green lights made them useful as a germicidal light.
The greatest issue in keeping these arc lights operating was the movement/feeding of the carbon rods to keep them arranged with the appropriate gap for the arc to jump across. An arc lamp of that design will eventually fail as the gap between rods is ultimately increased as they are vaporized by the electrical arc. The first lights were kept burning by using insulated pliers to grip and physically move the rods to maintain the proper gap. This action of moving the rod, or rods, was known as “trimming”, and the solution to moving them by hand was to utilize feeding devices which were clockwork-like devices which used gearing, clutches and other mechanisms to move the rods at a specific rate in order to keep pace with the vaporization of the rod ends. The different devices and approaches involved in the numerous developments of the rod feeding devices is a huge subject in itself. The best system of the times was ultimately developed by the Thomson-Houston Company. Eventually more sophistication ruled and the rods were advanced by a system that sensed the voltage and current draw changes as the gap widened. Magnets and other devices reacted to the changes and kept the gap a constant size, enabling the lights to burn, unattended, for many hours. In an attempt to make the lights burn longer, many experiments with rod composition were conducted. It was eventually determined that by copper plating the carbon electrode, the lamp could then burn for days instead of hours. The flame arc lamp was the next evolution of these lights, which allowed for much longer overall life and a much longer period between rod gap adjustments and replacements. In 1904, carbon rods started being made which had a very high content of magnetic oxides of iron, with titanium carbide and titanium oxide often added as well; these rods were the height of sophistication for the arc lamp.
Readying the arc light for user friendly commercial use was a process which covered many years. The biggest reason the lights were initially used on a limited basis was because reliable power systems were not readily available. The power used for these lamps in the day was initially DC batteries. There were not many consumers using the systems as the technology was quite primitive and the batteries were very costly, not very reliable and had short lives. Zenobe T. Gramme’s dynamo/generator, which he developed in 1871 – some sources say 1869 – started a race among other inventors to develop differing dynamo designs, all of which helped with the first true successful commercialization of artificial lighting. The first truly useful carbon arc lamp was the Yablochkov (Jablochkoff) candle which contained two perpendicular carbon rods which were placed parallel to each other at a distance that provided the correct gap (hah, what a revelation!). The rods burned from the top down. Obviously, this arrangement allowed for a much more self-sustaining lamp as the carbon rods did not need to be constantly moved together to retain the correct arc gap. Once the rods were completely vaporized, it was a simple task to replace them. The light produced by these devices was inconsistently bright and wavered between bright white and dark purple, and sometimes they just went out. If this occurred and other lamps were part of the system, they too would cease to operate as the systems were arranged in series connections (think of a string of Christmas lights which would die if one light in the string was burned out). Despite all the drawbacks that were associated with the lights, they were the real beginning of commercially available lighting.
This blog is a multi-part writing which will touch on the evolution of artificial lighting and will be continued in the upcoming weeks. In the meantime, if you need help with your LED lighting projects, please feel free to call Polar-Ray at 303-494-5773 and speak with a lighting consultant.