Neon Lighting Display Made of Glass Tubes:
A Neon sign is a Lighting Display made of glass Tubes that have been filled with a Gas
and bent into the shape of letters or decorative deSigns. When a high-voltage Electrical
current is passed through the Gas, the Tubes emit Light. Although Neon Gas was originally
used in these Signs, several other Gases are also used.
Although Neon Gas was originally used in Neon Signs, it is now only used to produce
reds and oranges. Argon, or an Argon-Neon mixture, is used in most Signs. To improve
the intensity of the Light, a small amount of mercury is added to the Argon to produce
an intense blue Light.
The Electrodes in each end of a section of illuminated tubing are usually made from
very pure iron surrounded by a cylindrical glass jacket or envelope with one end open.
A wire is attached to the metal electrode and passes through the closed end of the
glass envelope. The closed end is sealed into the end of the sign tubing with the
open end protruding into the Tube.
With only a Neon Signfew exceptions each sign is unique and must be designed
to fit the desired Display within the confines of the available space. Considerations
of the diameter of the tubing, the minimum radius the tubing can be bent, and the
overall length of tubing the transformer can power all limit the final design. For
example the smaller the diameter of the tubing, the brighter the Light. Conversely
a smaller diameter tubing requires more power, thus limiting the over-all length
of tubing one transformer can handle.
It consists of bending the tubing and attaching the Electrodes, removing any
impurities from within the tubing, then evacuating the air and adding the Gas.
Preparing the tubing:
Lengths of glass tubing are cleaned and placed vertically in a coating machine.
The machine blows a liquid phosphor suspension upwards into the Tube and then lets
it drain back out the bottom. The Tubes are placed vertically in an oven which dries
the coating. Color tints are applied in a similar manner. Tubes that are to be
filled with Neon to form a red or orange Light or Argon
to form a blue Light are left clear.
Bending the tubing:
The glass tubing is carefully heated and softened using a variety of burners. Smaller
hand torches are used to heat shorter lengths. Using the asbestos template as a guide,
the tubing is bent by hand. The Tube benders do not wear protective gloves because
they must be able to feel the heat transfer and the degree of softening in the glass
to determine the right moment to make the bend. Tube bender attaches a short length
of flexible hose, called a blow hose, to one end. The Tube bender gently blows
into the hose to force the tubing back to its original diameter. Tubes with
restricted diameters will not operate properly.
Several Sections of Glass Tubing:
Most large Neon Signs are made of several sections of glass tubing. To make each section,
the ends of two lengths of tubing are heated and spliced together. When the shape of
the lettering or design has been formed for a section, an electrode is heated and
fused onto each end. A small port, called a tubulation, is added to allow the tubing
to be evacuated with a vacuum pump. This tubulation port may be part of one of the
Electrodes or may be a separate piece joined into the tubing.
A process known as bombarding is used to remove any impurities from the glass,
phosphors, and Electrodes. First the air inside the tubing is evacuated. After the
vacuum reaches a certain level, dry air is allowed back into the tubing until
the pressure is in the range of 0.02-0.04 inches (0.5-1.0 mm) of mercury.
A very high-current transformer is connected to the Electrodes. For a length of tubing
that may normally run on 25 milliamperes, 350-700 milliamperes may used for the
bombarding process. The high current heats the glass to about 400°F (216°C), and the
metal electrode is heated to about 1300°F (750°C). This heating forces the impurities
out of the materials, and the vacuum pump carries the impurities out of the system.
Filling the Tube:
Once the Tube has cooled, the Gas inserted under low pressure. The Gas must be
free from impurities in order for the sign to operate properly and have a long life.
The normal fill pressure for a Tube 0.6 inches in diameter is about 0.5 inches of
mercury. Tubulation port is then heated and sealed off.
Aging the Tube:
The finished Gas-filled tubing is put through an aging process. Sometimes this process
is referred to as "burning in the Tube". The purpose is to allow the Gas in the Tube
to stabilize and operate properly. A transformer, rated sLightly higher than the normal
operating current is attached to the Electrodes. The Tube should come to full
illumination within 20 minutes if Neon is used. It may take few hours for Argon.
If a small amount of mercury is to be added to an Argon Tube, The droplet is rolled
from one end to the other to coat the Electrodes after the aging process. Any problems
such as a flicker in the Gas or a hot spot on the Tube indicate the tubing must be
opened and the bombarding and filling processes repeated.
Installation and Mounting:
Small Neon Signs are Mounted on their framework and wired in the shop. Larger Signs
mounted in pieces and put into the building, other support structure where they are
interconnected and wired. Large installations require months to install.
Careful manufacturing process required to produce a properly operating Neon sign. Neon
sign should have a life of over 30,000 hours. As a comparison, the average 100-watt
Light bulb has a rated life of 750-1,000 hours.
Series of Tests:
This requires a series of Tests. Neon Signs must also meet the requirements of the
National Electrical Code. Outdoor Signs must comply with local building codes in
their construction and Electrical wiring.
Wishing you all the best,