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EVOLUTION OF MODERN LIGHTING
Light fascinates us all with its ability to define color, texture and form, as well as its
capacity to shape emotional response. Yet lighting is one of the most difficult components
of interior and industrial design to get right. Its principles involve a complex
comibnation of art and science, technical precision and emotional perception.
TECHNOLOGICAL ADVANCES
To understand the pattern of design development in lighting in this century, it is
necessary to know in broad outline the technology on which it has been based. Thomas
Edison, the great American inventor, is the first, and certainly the best-known, figure
in this story. "We will make the electric light so cheap that only the rich will be
able to buy candles," he exclaimd shortly after conducting an experiment in October 1897
at Menlo Park, New Jersey, with device which was the prototype of the tungsten-filament
bulb.
Edison was a tireless inventor who took out no less than 1,093 patents during his lifetime
for devices including the electric pen, the phonograph, waxed paper, and, of course, the
incandescent electric lamp. In 1878 he had formed the Edison Electric Company, forerunner
of General Electric, and conducted research into ways to develop a lamp or bulb with a
resistant filament. Early attempts burnt out but, when he replaced alumninum filaments
with carbon ones the following year, the achieved a breakthrough. The first commercially
viable electric lamp, then, comprised a carbon-wire filament in a glass bulb from which all
air had been evacuated; the ends of the wire were drawn through a sealed cap to the
electric supply. When the supply was connected, the filament glowed, providing visible
light. The vacuum within the bulb slowed down the process of oxidation which ultimately
destroyed the filament. When Edison's achievement was heralded on the front page of The
New York Herald in December 1897, gas stocks and shares plummeted on Wall Street.
However, a carbon-filament lamp was also being created on the other side of the Atlantic at
the same time. In 1878 the English inventor Joseph Swan conducted an experiment which
heated the filament while evacuateing gases from a vacuum-filled glass envelope. By 1880
the first domestic lighting system using filament bulbs was seen in Britain; they were
installed at the fashinable new Northumbrian home of British armaments millionaire Lord
Armstrong.
Edison and Swan sensibly decided to join forces. They formed the Edison and Swan United
Lamp Company, later known as Ediswan. Each had invented his own method of fixing the
light bulb to the supply circuit: Edison patented the screw-in brass cap; Swan devised a
bayonet fitting. Both are in use today.
But although the carbon-filament bulb was a significant advance on the oil and gas lighting
of the 19th century, it lacked durability and efficiency. Research focused on improving
the filament, and a number of metallized alternatives emerged. Then, in 1908, William
Coolidge, a New York scientist with the General Electric Research Laboratory, found a
solution. He produced commercially practical tungsten filaments which could be drawn to
specific diameters and which were rugged enough to withstand the shocks and vibrations of
the street and railroad cars of the period.
In 1913 Coolidge's associate, Irving Langmuir, solved the problem of the blackening of the
bulb as the tungsten glowed. It was caused by early tungsten- and carbon-filament wire
alike when molecules of filament migrated to the bulb, reducing efficiency. The
introduction of the double-coiled filament significantly increased bulb life.
The important pioneering work on the tungsten-filament bulb, mainstay of 20th-century
domestic lighting, was complete. Despite a continual process of innovation and updating,
the next major breakthrough in the field did not come until 1959 when the first practical
tungsten-halogen lamp was develped in the USA by Zuber and Moser.
Meanwhile the big rival to the tungsten-filament bulb in the home, the fluorescent tube,
was not introduced until 1938. But when General Electric launched it on the American
market, it had an immediate impact: it was more energy efficient, longer lasting and cooler
than tungsten. This was because it radiated light in a different way. The fluorescent
lamp comprised a glass tube coated with phosphors and filled with a mixture of argon and
mercury vapour. Metal electrodes were positioned at either end and when current flowed
through the gas between them ultraviolet radiation was produced. The phosphor coating
absorbed the radiation and fluoresced.
Fluorescent created a host of new opportunities for lighting designers but its light was
seen in some quarters as cold and unsympathetic. It was regarded as ideal for offices or
factories, and for functional areas of the home, such as kitchens or garages. But it
lacked the warmth and colour fidelity of tungsten sources.
With the advent of tungsten-halogen in the 1960s, designers were similarly freed from the
traditional constraints of Edison's and Swan's invention. Mains-voltage tungsten-halogen
bulbs last twice as long as conventional tungsten-filament bulbs without sacrificing any
of the color quality. They are also marginally more energy efficient. Improved
performance is due to a regenerateive process within the tungsten-halogen bulb. The
addition of halogen gas further reduced the migration of tungsten molecules, which interact
with halogen and redeposit themselves on the glowing filament. The chemical effect of
halogen on glass necessitates a quartz lamp.
But the real revolution in tungsten-halogen lighting has been in low-woltage rather than
mains-voltage systems. The 1980s saw the widespread introduction of ultra slim fittings
capable of bearing intense pin-beams of light. Low-voltage tungsten-halogen has completely
revised the minimum dimensions required to hold and direct a light source: now tensile
wires drawn across a ceiling can constitute a light fitting, so small are low-voltage
light sources.
Low voltage has proved itself adept in display and discreet accent lighting, especially in
shops. But now it is becoming popular in space-conscious homes. A transformer is needed
to convert the electric current from mains to low voltage, something light-fitting designers
must take into account.
Other light technologies have momentarily diverted the course of modern lighting design.
But neon, high-pressure sodium and metal halide lamps have all proved inappropriate for
large-scale domestic use, and for the most part, 20th-century lighting has developed against
the backdrop of advances in tungsten, tungsten-halogen and fluorescent.
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