The
concept behind neon signs was first conceived in 1675,
when the French astronomer Jean Picard observed a faint
glow in a mercury barometer tube. When the tube was
shaken a glow called barometric light occurred, but the
cause of the light (static electricity) was not then
understood.
History Note:
Jean Picard is better known as the astronomer who
first accurately measured the length of a degree of
a meridian (longitude line) and from that computed
the size of the Earth. A barometer is a device used
to measure atmospheric pressure, there are two main
types of barometers: mercury and aneroid.
Evangelista Torricelli invented the barometer in
1643.
Even
though barometric light was not yet understood, it was
investigated. When the principles of electricity were
discovered, scientists moved forward towards the
invention of various forms of lighting. By 1855, there
was the geissler tube named after Heinrich Geissler, a
German glassblower. Gas in the tube was placed under low
pressure and electrical voltage was applied, the result
was that the gas glowed. After electrical generators
were invented, many people experimented with applying
electric power to tubes of gas. Several electric
discharge lamps or vapor lamps were invented from 1900
onwards in Europe and the United States. Simply defined
the electric discharge lamp is a lighting device
consisting of a transparent container within which a gas
is energized by an applied voltage, and thereby made to
glow.
The
French engineer, chemist, and inventor Georges Claude
(b. Sept. 24, 1870, d. May 23, 1960), was the first to
apply an electrical discharge to a sealed tube of neon
gas (circa 1902) to create a lamp. The word neon comes
from the Greek "neos," meaning "the new gas." Georges
Claude displayed the first neon lamp to the public on
December 11, 1910, in Paris. In 1923, Georges
Claude and his French company Claude Neon, introduced
neon gas signs to the United States, by selling two to a
Packard car dealership in Los Angeles. Earle C. Anthony
purchased the two signs reading "Packard" for $24,000.
Neon lighting quickly became a popular fixture in
outdoor advertising. Visible even in daylight, people
would stop and stare at the first neon signs dubbed
"liquid fire."
History Note:
Before there were neon signs in America, there were
commercial sign tubes that used a carbon dioxide
fill. The carbon dioxide signs were made by a man
called Moore. Neon gas was discovered by William
Ramsey and M. W. Travers in 1898 in London. Neon is
a rare gaseous element present in the atmosphere to
the extent of 1 part in 65,000 of air. It is
obtained by liquefaction of air and separated from
the other gases by fractional distillation.
Making
a Neon Sign -Hollow
glass tubes used to make neon lamps come in 4, 5 and 8
ft lengths. To shape the tubes, the glass is heated by
lit gas and forced air. Several compositions of glass
are used depending on the country and supplier. What is
called 'Soft' glass has compositions including lead
glass, soda-lime glass, and barium glass. "Hard" glass
in the borosilicate family is also used. Depending on
the glass composition, the working range of glass is
from 1600' F to over 2200'F. The temperature of the
air-gas flame depending on the fuel and ratio, is
approximately 3000'F using propane gas.
The tubes are scored
(partial cut) while cold with a file and then snapped
apart while hot. Then the artisan creates the angle and
curve combinations. When the tubing is finished, the
tube most be processed. This process varies depending on
country; the procedure is called "bombarding" in the US.
The tube is partial evacuated of air. Next, it is short
circuited with high voltage current until the tube
reaches a temperature of 550 F. Then the tube is
evacuated again until it reaches a vacuum of 10-3 torr.
Argon or neon is back filled to a specific pressure
depending on the diameter of the tube and sealed off. In
the case of an argon-filled tube, additional steps are
taken for the injection of mercury; typically, 10-40ul
depending on tube length and climate it is to operate
in.
Red is the color neon
gas produces, neon gas glows with its characteristic red
light even at atmospheric pressure. There are now more
than 150 colors possible; almost every color other than
red is produced using argon, mercury and phosphor. Neon
tubes actually refer to all positive-column discharge
lamps, regardless of the gas filling. The colors in
order of discovery were blue (Mercury), white (Co2),
gold (Helium), red (Neon), and then different colors
from phosphor-coated tubes. The mercury spectrum is rich
in ultraviolet light which in turn excites a phosphor
coating on the inside of the tube to glow. Phosphors are
available in most any pastel colors.
Source: Mary Bellis
|