Preconditions to 20th Century Lamps
"I remember this circumstance very well because of the excitement and surprise and incredulity which he manifested at the time. He asked me over and over again what it
(William D. Coolidge, General Electric scientist, 1909)
Coolidge was recounting Fritz Blau's reaction to a lamp made with bendable (or
"ductile") tungsten wire. Blau, an Austrian, had helped invent a "non-ductile" tungsten
lamp only a few years earlier and knew well the difficulty of working with this metal.
Coolidge's lamp was not the first improvement in Edison's design, nor the last. It built
on previous work (such as Blau's) and fueled new work (such as Irving Langmuir's).
Inventors in the late 20th century had access to technical information unknown in
Edison's time. Some knowledge came from outside the industrylike phosphor work
done for television. But lighting scientists and engineers made many discoveries in the
first half of the century, especially in the new industrial laboratories inspired by Edison's
Menlo Park and West Orange labs. Research into the physics of electrical discharges,
the metallurgy of tungsten, and chemical properties of glass all played a role in creating
lamps that became available in the 1930s.
As the technology matured however, the pace of major improvements slowed. Below
are some of the major developments of the 1900-1950 era important to lamps in use
Incandescent Lamps: Exit CarbonEnter Tungsten
Non-ductile tungsten lamp
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By 1900 the carbon filament lamp was a mature product in mass production. Electrical
efficiency (or "efficacy") remained very low at about 3.5 lumens per watt (lpw). Aside
from wasting electricity, these carbon lamps simply did not provide strong light.
Inventors, especially in Europe with its high energy costs, searched intently for new
Though carbon has the highest melting point of any element, the operating temperature
of carbon filament lamps had to be kept relatively low. Very high temperatures caused
carbon to evaporate quickly from the filament and coat the inside of the bulb, dimming
an already low light. Experiments with various metals were aimed at finding a material
that could operate at a higher temperature without so much evaporation. Higher
operating temperatures meant brighter, more energy efficient lamps.
Carl Auer van Welsbach of Austria (inventor of the gas mantle) developed the first
commercially practical metal filament lamp in 1898 by making filaments with element #
76, osmium. The very brittle filaments gave 5.5 lpw, a significant improvement, but
osmium lamps proved difficult and expensive to make. They were replaced in 1902 by
lamps invented by Germans Werner von Bolton and Otto Feuerlien, who used element #
73, tantalum. Tantalum lamps produced 5 lpw, a slight drop from osmium that was
more than offset by tantalum's greater strength.
Tantalum was in turn superceded by lamps made with element #74, tungsten. Another
difficult metal to work with, tungsten lamps like the one seen above gave 8 lpw, and in 1904 three different tungsten lamps
appeared on the European market almost simultaneously. American manufacturers licensed
and sold both tantalum and first generation tungsten lamps in the U.S.
Many of Edison's carbon lamp patents were expiring around this time and competition
was heating up. In 1904, Willis Whitney used the new electrical resistance furnace at
GE's Schenectady lab to bake carbon filaments at very high temperatures. The
resulting filaments exhibited metal-like properties and gave 4 lpw. Sold as the "General
Electric Metallized" or "GEM" lamp, this lamp still achieved only half the efficacy of the
new tungsten lamps from Europe.
William Coolidge, also at GE's research lab, began exploring the metallurgy of
tungsten. The European lamps were almost as fragile as earlier osmium lamps
because tungsten was too brittle to bend ("non-ductile"). Coolidge developed a process
to make bendable ("ductile") tungsten wire, and in 1910 GE began selling lamps made
with this filament. The lamps gave 10 lpw, and also gave GE strong new patents.
Coolidge's colleague, the future Nobel laureate Irving Langmuir, discovered that by
coiling the tungsten filament and placing an inert gas like nitrogen inside the bulb he
could obtain 12 lpw or better. Langmuir's lamp joined Coolidge's on the market in 1913,
both selling under the "Mazda" trade-name.
Various improvements in both the tungsten lamps themselves and in production
machinery occurred during the following forty years. These cut costs drastically but
improved lamp efficacy only slightly. By 1950, tungsten lamp technology seemed at a
dead-end, especially given the growth of discharge lamps like fluorescent tubes. Some
older engineers began advising younger colleagues to avoid staking a career on
Discharge Lamps: Lightning in a Tube
Cooper Hewitt tube
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An interesting curiosity of the 19th century were devices called Geissler
glassblower Heinrich Geissler and physician Julius Plücker discovered that they could
produce light by removing almost all of the air from a glass tube and then sending an
electric current through the tube as an arc discharge. Poor seals allowed air to seep
back in and extinguish the light, but the work spurred research into discharge lighting.
In the first decade of the 20th century, two commercial discharge lamps gained modest
popularity. One, invented by American D. McFarlan Moore, used carbon-dioxide or
nitrogen filled tubes up to 250 feet long. Moore tubes were more efficient than carbon
filament lamps but difficult to install and maintain. A second lamp, invented by American
Peter Cooper Hewitt, passed an electric current through mercury vapor. Cooper Hewitt
lamps (above) gave off much light and could be made portable, but the light was a garish blue-green suitable for few uses. These lamps contained about a pound of mercury each.
Coolidge's and Langmiur's tungsten filament lamps of the 1910s raised the efficiency
standard for all lighting devices. Moore lamps, for one, soon disappeared from the
market. Research indicated that very high efficacies might be attainable with discharge
lamps however, so work continued.
Building on Moore's work, Georges Claudé of France developed neon tubes in 1910
and showed that a discharge lamp could give 15 lumens per wattif one wanted red
light. Additional European work resulted in a high-intensity mercury vapor lamp (from
General Electric Company of England) in 1932. This lamp used a tiny fraction of the
mercury needed for Cooper Hewitt lamps, had a screw base, and gave 40 lpw, though
its color was still poor.
A collaboration of GEC in England, Philips in The Netherlands, and Osram in Germany
produced a low-pressure sodium lamp also in 1932. The key to this lamp lay in a
special glass that could withstand the corrosive effects of sodium. The light was a stark
yellow suitable only for use in applications like street lighting, but efficacy started out at
40 lpw and reached about 100 lpw by 1960.
Reports began reaching GE and Westinghouse in the late 1920s and early 1930s of
French experiments with neon tubes coated with phosphors. A phosphor is a material
which absorbs one type of light and radiates another. A German patent in 1927
contained most of the features of a fluorescent tube, but the lamp was not produced.
American scientist Arthur Compton, a consultant to GE, reported seeing a green French
lamp giving 30 lpw in 1934. An engineer at GE later wrote that they thought Compton
had misplaced a decimal, that the true figure was 3.0 rather than 30 lpw.
The figure, soon confirmed, sparked an intensive research program. In 1936, tubes
using low-pressure mercury vapor and a coating of phosphors were demonstrated to
the Illuminating Engineering Society and the U.S. Navy. In 1939, GE and Westinghouse
introduced fluorescent lamps at both the New York World's Fair and the Golden Gate
Exposition in San Francisco. Other lamp makers soon followed.
Despite resistance from some utilities fearing loss of electricity sales, the need for
efficient lighting in U.S. war plants resulted in rapid adoption of fluorescent technology.
By 1951 industry sources reported that more light in the U.S. was being produced by
fluorescent lamps than by incandescent.
Research After Edison: "The Science of Seeing"
Thomas Edison's lamp research focused mostly on the chemistry and engineering of
the light bulb itself and its interaction within an electrical system. As researchers began
building on Edison's work, the topics broadened to include subjects like optics and the
physics of light itself. Edison, intent on inventing, cared little for basic research, but new
professional "illuminating engineers" explored the fundamental nature of light and
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For example, as metal filament lamps began replacing carbon lamps, the problem of
glare arose. Shades for the brighter tungsten lamps had to be designed to both protect
eyesight and to more effectively channel light. New applications like automotive and
aviation lighting required development of a host of new lamp designs with special
electrical and optical characteristics.
Researching human eye response to different colors and light levels became more
important as electric lighting began to change people's lifestyles. Questions about the
affect of lighting on productivity in both workplace and home carried great economic
significance. Development of fluorescent lamps in the late 1930s led to experiments
with "windowless factories."
The 1906 establishment of the Illuminating Engineering Society marked a formal
recognition that lighting had moved from the realm of lone inventors to that of a
profession. Corporate and academic researchers not only presented their work in the
form of patents, but also wrote papers that appeared in scholarly journals. A prominent
researcher, GE's Matthew Luckiesh described the field as "The Science of Seeing."
Researchers produced light distribution curves for fixtures (above), studied how different
consumer groups used light, and developed deeper understandings of the fundamental
nature of light. Expensive research equipment, needed to pursue these issues, made it
difficult for smaller companies to compete. Lighting design emerged as a special field,
distinct from architecture, just as lighting engineers diverged from electrical engineers.
Lighting and radio were the two electrical products that sold well throughout the Great
Depression, justifying continued investment in research. The onset of World War
II provided stimulated research for military uses of lighting, especially into materials like
quartz and ceramics, while blackouts and materials rationing held back civilian
purchases. Finally, the postwar economic boom released tremendous demand for
lighting. The result proved to be a burst of lighting innovation.