Lighting Technology: From Darkness to Opportunity April 11, 2001 Robert L. Smith, PE, FIES Robert Smith is a professor at the University of Illinois School of Architecture. Tracing the development of lighting technology can help designers to better appreciate and benefit from the full potential of today’s lighting. Until this generation, for example, cost was a major deterrent to providing interior illumination. Our forebears had to evaluate the cost of candles, lamp oil, and electric lamps in terms of hours of labor, but technological advancement has radically changed the real cost of providing interior illumination. A 14th-century English worker paid two-thirds of a day’s wages for a small candle. In most areas of the United States today a 100-watt lamp -- which provides 160 times the light of a candle -- can be operated for less than a dime for 10 hours, a period of time during which a person at a minimum wage would earn $35. The safety, convenience, and flexibility of contemporary lighting are also great improvements upon the lighting of our ancestors. THE BEGINNINGS No one knows how cave dwellers first illuminated the dark recesses of their homes. It is reasonable to assume, however, that the glow of a cooking fire was a common light source. For portable light, perhaps a burning bundle of sticks -- a fagot -- was used. The oldest known lamp was discovered in a cave in France. The 20,000-year-old sandstone bowl contained remnants of grease and a small piece of vegetable fiber that probably served as a wick. It is likely that natural objects were used even earlier. Perhaps bowl-shaped stones or sea shells were filled with the drippings from a cooked animal and a piece of moss or fibrous material was used as a wick. OIL LAMPS Lamps were fashioned from clay as early as 5000 years ago and either sun-dried or baked. Lamps were also made of gold or copper, but those were very rare. The metal lamp that has survived in greatest numbers is the iron "crusie," probably a Celtic lamp of early Iron Age origin. Originally, it was a single bowl device with a wick hanging from a pinched spout. Oil constantly dripped from the wick: the oil not only was wasted but also created a mess. The Scottish people are credited with adding a second bowl to catch the precious oil. Often called a "Phoebe" or a "pan lamp" -- and when fitted with a cover a "betty" lamp -- this was typical of the oil-fueled light sources used by working people for several centuries. The choice of fuels for these lamps depended mainly on availability, and a variety might have been used, including animal fat, fish oil, olive oil, vegetable oils, and natural petroleum seepages. There were definite preferences. Fish oil was used extensively, but the odor of its smoke would have been offensive. A Greek writer probably had fish-oil—fueled lamps in mind while writing, more than 24 centuries ago, "One could not enjoy the good things at the table until indulgence in the wine made the guests indifferent to the smoking lamps." By the middle of the 19th century, whaling fleets had greatly reduced the whale population, and sperm oil -- the preferred choice for lamps -- was beyond the reach of common people. In 1855, when raw sperm oil sold on docks in Massachusetts for S 1.70 a gallon, a construction laborer working on the Erie Canal earned $1 for a 10-hour day. CANDLES The place of candles in antiquity is often misunderstood. Far from commonplace, they were expensive and considered a luxury. The candle evolved from splinters of wood that were lighted and carried about. Usually two to three feet long, the splinters were cut from knot-free pine logs. Next came rushlights. In the fall, rushes were harvested, peeled, dried in the sun, and then dipped in kitchen fat. A pound of dry rushes, about 1600 stems over two feet long, and six pounds of fat would make enough rushlights to burn for about 800 hours. The candles of olden times were made of either tallow or beeswax, and the wicks were fibers from the papyrus or rushes. The wicks were coated by dipping, pouring, or forming in molds. Because the process was long and tedious, wax candles were labor- and material-intensive items and were therefore available almost exclusively to the wealthy and the churches. From the beginning of time to the late 18th century, only the light sources described above were available. The methods of lighting had important implications for the life-style of our forebears. LIGHTING IN ANTIQUITY Indoor lighting had a severe impact on living environments: walls and ceilings were discolored by smoke, and people lived in constant danger of grease drippings on the floor becoming ignited. As the accompanying table shows, all light sources produced about the same intensity of light; to get more light required multiple sources, such as a bundle of sticks or a chandelier. Light sources required a high level of maintenance. Rushlights and splinters needed regular replacement. Unless candles were snuffed every 5 to 20 minutes, "guttering" would cause most of the tallow to drain off and the candles would rapidly be consumed. It was also necessary to have or start a fire every time a light was wanted. A fire could be started only by rubbing sticks together or by using a flint, steel, and tinder, so people often “carried their fire.” It took about three minutes to start a flame with a tinder box, assuming the tinder was dry. The cost of lighting was a barrier to adequate illumination. Oils used for lighting were also useful for food. When the cost of food required 80 percent of a worker’s wages, little money would be used to provide light. Lighthouse keepers, it is recorded, often consumed large quantities of the tallow candles that were provided for use in the towers. A 14th-century Englishman paid twopence for a small (12 to the pound) tallow candle. During this same period a carpenter received threepence a day for his labors; wine was fivepence a gallon; fagots were thirtypence a hundred. Lean meat cost but a farthing (one-fourth of a penny) a pound, but the fat used in oil lamps and to make candles and rushlights was twopence a pound. According to a history of English agriculture, “A candle must have been a rare and choice personal luxury, and was used, as a rule, in the management of the farm only at the time in which the shepherd was attending to his ewes.” A PERIOD OF DISCOVERY Although virtually unnoticed at the time, a 1765 event marked the beginning of a new light source that would have a great impact on commercial activity. One Mr. Shedding piped gas from his coal mine to illuminate his office. He offered to install gas illumination on the streets of Whitehaven, England, but the city refused his offer. In 1792, William Murdoch perfected a method of heating coal to produce gas for lighting. In 1806, David Melville of Newport, Rhode Island, installed illuminating gas in a textile mill: this is believed to be the first commercial use of gaslight in America. Thus began an industry that was to provide lighting for working and residential environments for over a century. In 1784, Thomas Jefferson brought to America a lamp designed by Swiss chemist Ami Argand. Argand had developed a tubular wick, introduced air in its center, put a straight glass chimney over the flame for better draft, and created a light source of six- to eight-candlepower intensity. Ironically, this increase in intensity -- to a level well below that of present day sources -- was greeted with some concern. The 1804 edition of the Domestic Encyclopaedia published this caveat about the Argand lamp: “As the light emitted from them is frequently too vivid for weak or irritable eyes, we would recommend the use of a small screen.” During the 19th century, the pace of lighting technology suddenly began to accelerate. After Sam Jones marketed the “Lucifer” in 1829, people could “carry the fire” in the form of a match. Between 1830 and 1860, approximately 500 patents for lighting devices were recorded in the United States Patent Office, including several new fuels. In 1830, Isaiah Jenkins patented his “burning fluid,” a combination of alcohol and turpentine. Samuel Rust of New York patented several improvements in wicks and chimneys. Then, in 1839, Augustus V.X. Webb began to manufacture distilled turpentine under the name camphine. These fuels were very volatile and the resulting explosions resulted in many unfortunate deaths. Kerosene, often called paraffin oil or coal oil, was discovered by Abraham Gesner, of Williamsburg, New York, in 1845. With the 1859 development of the oil fields in Pennsylvania, a new era of lighting was opened; even the poor could have lighting in their homes. At the same time that gas and fluid fuels for use in lighting devices were being developed, electricity and the possibility of an incandescent lamp were being explored. In 1802, Sir Humphry Davy used electricity to heat thin strips of metal to incandescence, but they quickly oxidized. In 1841, the British government granted the first patent for an incandescent lamp to Frederick De Moleyns. In 1859, Professor Moses Farmer illuminated the parlor of his home in Salem, Massachusetts, using a platinum wire in open air as did many others of the day. But, it was as short-lived and impractical to operate as the other electric lamps of the day. THE EDISON ERA An 1879 event marked the beginning of a new era in lighting technology and design. In a laboratory close to Menlo Park, New Jersey, Thomas Alva Edison applied electric current to a slender carbonized cotton thread mounted in an evacuated glass bulb. The lamp burned brightly for two days, until Edison increased the voltage, overheating and destroying the filament of his latest invention. Edison was inventing not just an electric light, but an entire electrical system for illuminating homes and businesses. During the next three years, Edison and his dedicated assistants invented and developed a comprehensive system of electric generation, control, distribution, measurement, and utilization that made possible the opening of the Pearl Street Central Station on September 4, 1882. This New York City facility began operation by supplying 85 customers with a connected load of about 400 incandescent lamps. These 16-candlepower lamps sold for $1 each: the young women hired to make them were paid on a piecework basis -- and earned from 50 cents to 70 cents per day. One of Edison’s first customers was the New York Times, where 52 lamps were installed in the editorial office. The Times reported the effect as being “soft, mellow, grateful to the eye; it seemed almost like writing by daylight.” The first customers were not charged for the energy, so it was January 18, 1883, before a bill was collected -- from Ansonia Brass and Copper Company for $50.40. The connected load increased until for the month of November the collections had increased to $9102.45 and as of December 1, 1883, there were 10,297 lamps in operation. Tragically, the station and all the equipment, except for one generator, were destroyed by fire in 1890. The generator from the Pearl Street Central Station can now be viewed at the Greenfield Village & Henry Ford Museum in Dearborn, Michigan. Edison was not alone in his endeavors to provide lamps and to install lighting systems. In fact, competition was fierce in the United States and abroad, which brought about rapid improvements in the equipment and techniques used to provide the lighting systems. The incandescent lamps first marketed had free-blown bulbs with seal-off tips, a looped or hairpin shaped carbon filament, and any one of a dozen different bases, which were filled with plaster of Paris. But, 70 percent of them used Edison screw bases, so that eventually became the standard. In 1898, machinery was developed to assist the glass blowers; after that most bulbs had straight sides. In 1901, black glass replaced the plaster of Paris in the base. Then, in 1905, the GEM (General Electric Metallized) lamp was introduced; it was rated in watts instead of candlepower. The tantalum filament, marketed in 1906, was quickly replaced by the tungsten filament in 1907. In 1922, the seal-off tip was eliminated, and the last vestige of that first incandescent lamp had disappeared. TIME OF OPPORTUNITY Today the lighting industry is equipped to design lighting systems that were beyond fantasy when the Argand lamp appeared just two centuries ago. Five types of lamps are available to lighting designers: incandescent, fluorescent, high intensity discharge, high pressure sodium, and neon. Incandescent lamps. Although incandescent lamps are now 10 times as efficacious as the first lamp, they are still the least efficient of these sources and still produce less than 20 lumens of light for each watt of power. Incandescent lamps are, however, especially useful where usage is low, where precise control of light is required, or where a very small source is needed. The multireflector (MR) 16 lamp, for example, is ideally suited to applications that need a lot of light on a very small area. Although the lamp with reflector is but 2 inches in diameter, it may provide from 20 to 75 watts. The tungsten halogen (quartz) light source provides a concentrated beam. The 20-watt narrow beam lamp will put 33 footcandles on a surface 10 feet distant. Its color characteristics are considered excellent. Bud lamps are another judicious use of an incandescent source. These lamps, usually 1 watt, are installed in tubes or on a tape and provide exciting decorative lighting that requires only very low power. Fluorescent. Designers can choose from a seemingly unlimited array of fluorescent lamp types. The main variations are in lamp current (affecting the lumen output), color characteristics, size (length, diameter), and shape. Energy-efficient fluorescent systems can produce 85 or more lumens per watt. Fluorescent is recommended for applications in which diffuse ambient illumination is needed, where task illuminance is required on a specific area, and where color rendition is a major goal. The triphosphor lamp is of particular interest to discriminating designers; it provides both excellent color rendition and a visual clarity that is not achievable with other sources. Although it is more costly than other types, it is very popular in merchandising. A new addition to the fluorescent family is a low-wattage lamp that may be used as a replacement for incandescent lamps with an efficacy of three to four times that of incandescents. The lamp also has a life rating more than 10 times that of the incandescent. High intensity discharge. Metal halide sources belong to the high intensity discharge (HID) family. The use of this lamp -- which is a high intensity, point source -- should he limited to installations in which the light source is out of the field of view. It is ideal for spaces with high ceilings or in indirect lighting applications. An excellent lamp from art energy standpoint, its efficacy exceeds 80 lumens per watt. High pressure sodium lamps. The highest efficacy sources discussed here are the high pressure sodium lamps, with values exceeding 100 lumens per watt. Available in a wide range of sizes, from 35 watts, these lamps are a preferred choice for security lighting and for large spaces where color rendition is not critical. Using them alongside metal halide lamps improves the color characteristics of the illumination. Neon. As the generic name for a large family of electric discharge lamps, neon includes cold cathode, whose light output can he best described as a glow. Available in a wide variety of colors, the lamps can be sculptured to fit almost any configuration. They are ideal for providing soft ambient lighting, to enhance architectural elements, and as sculpture elements. DESIGNERS’ CHOICES Once a lamp has been chosen, a luminaire must be selected to support the lamp, to provide a connection to electrical power, and to provide specific control of the lamplight. Designers today can choose among a multitude of luminaires for any lamp; their task is to locate those that meet their space and task criteria. Then they must sort through the array and identify the luminaire that will put the lamplight where it is needed, efficiently and without affecting the environment adversely. The final hardware selection can be one of the most challenging and exciting design experiences. Electrical control choices for illumination systems range from simple toggle switches to exotic automatic control systems. Beyond the traditional manual switching devices are many choices. There are relay-operated low-voltage systems that permit manual or automatic (including computerized) positive control and electronic systems that impose a signal on the power wiring that initiates relay operation at the load site. Some space monitors are sensitive to motion or to heat. Others are operated by photocell devices that monitor a space’s illumination and maintain it at a preset level, whether the light changes because beneficial daylight intrudes or because the lighting system is aging. AUTOMATION’S POTENTIAL To appreciate the potential, imagine walking into an office early in the morning to find the lights automatically turned on to a preset intensity and the sheers covering the windows already raised. As the available daylight increases, the lamplight lessens. But, if direct sun intrudes into the work area, a motorized shading system lowers a sheer over the windows -- just far enough to block the undesirable direct sun. In this demonstration office, when the worker’s computer is turned on, the lamplight is decreased and the sheers adjusted until the illumination is correct for working at the video display terminal. Should an important guest arrive, a voice command can raise the sheers to expose the vista and modify the lamplight to create the right ambience for conversation. Lamplight is extinguished when the occupant leaves the office, and, depending upon the outside temperature, the sheers may be lowered to increase the thermal efficiency of the window. Throughout the day the conditions in the work environment have been optimized. When a high level of illumination was needed it was provided, but when the maximum lamplight was not necessary it was reduced to the proper value and energy was conserved, all with a minimum of action by the occupant. Designers have recently gained increased understanding of the way illumination of a space affects its occupants’ psychological reactions and productivity. This understanding has led to new technology to predict the quality and quantity of illumination in spaces being designed. Equipment that measures illumination in existing spaces and provides information for proper evaluation is also available. Although much of the technology and many of the measuring devices have been available for several years, the microprocessor has now made them affordable and therefore accessible. COMPUTER ANALYSES Software packages are now available that can create a lamp and luminaire data base for instant and repeated use. Then, using as many as eight different luminaires arranged in as many as 10 different layouts, the program will compute the illuminance at 400 points on the work plane, in four viewing directions, with or without body shadow. It will compute the equivalent sphere illumination (ESI) at 400 points in four viewing directions, the vertical illuminance in four viewing directions at each of the selected points, the illuminances on all the room surfaces, the exitances (luminances) for all the room surfaces, and the contrast at selected points, then give a statistical analysis of the data. After the computations are complete, the information may be displayed in tubular form, by isocontour lines on a graphic representation of the area being exhibited, or by a gray-scale shading on which dark shading represents low values and progressively lighter shading represents increases in lighting. In just a few minutes, a user can input several alternate lighting design schemes, execute the program, and have a full set of exhibits that will permit the selection of the best design scheme. An equally impressive set of tools is available to evaluate the character of the illumination in existing space. There are illuminance measurement instruments with digital displays, luminance measurement devices (both averaging and precise 1-degree spot meters), chromaticity meters to measure the light source color, and contrast-ESI meters. There are even contrast rendition meters that can be used to measure the precise effects of an illumination system on the readability of a cathode ray tube. One meter with enormous potential for evaluating illumination simultaneously measures and records 20 characteristics of lamplight, including color attractiveness, color rendering index, color scheme stability, color temperature, chromaticity, color preference index, brightness units, visibility units, and visible, violet, and ultraviolet efficacy and density -- everything you wanted to know about the illumination but didn't dare to ask. LUMEN COMPARISONS Source Tallow candle Beeswax candle Paraffin candle Whale oil, flat wick Whale oil, Argand lamp Kerosene table lamp Coal gas, #1 jet Edison carbon lamp Tungsten 50-watt (1909) A19 50-watt incandescent LU50 50-watt high pressure sodium Lumens * 12.5 11.5 14.9 9.0 98.0 60.0 30.0 160.0 400.0 530.0 3800.0 * Although these values, taken from several sources, were not verified, they are believed to be reasonable for comparison. TODAY'S CHALLENGES For an eon, progress in lighting technology was static. After a century of searching and discovery, and another century of invention and development, designers are at the threshold of an era in which hardware and knowledge will permit the design of affordable illumination systems that can increase productivity and pleasure in working and living environments. For an impressive example, think of the amount of light that can be afforded in terms of its potential to increase productivity. Assume that a $20-per-hour employee occupies 100 square feet of office space, electricity is 10 cents per kilowatt hour, the room is illuminated uniformly for tasks, and a combination of energy-efficient fluorescent lamps and ballasts are used with a luminaire to provide 35 lumens per square foot per watt in the room. For each hour that this employee can increase productivity by 1 percent, it would be economically feasible to increase the illuminance in the space as much as 666 footcandles. This example clearly illustrates that when productivity is at stake it is a poor gamble to deprive employees of the illumination that they need. No other technological development has had as profound an effect on human life-styles as the invention of electric illumination. Those who may suggest that the automobile has had a greater impact should be reminded that without electric lighting the auto would be a diurnal creature. Skillfully, abundantly, judiciously provided electric light can create environments that enable us to live better, more productive lives. November 1986, Architectural Lighting Magazine