This is a double-coiled tungsten filament light bulb manufactured from 1935 to this day as a high-wattage tip-less bulb. Like single-coiled filaments, double-coiling the single-coil filament further increases the effective filament length (in order to increase the wattage) without taking up more space. Its development was the last step resulting from Dr. William D. Coolidge’s
hard work in creating a bright, glowing ductile tungsten filament. The double-coiled filament bulb is likely filled with a mixture of nitrogen and argon gas at a pressure of slightly less than 1 atmosphere to reduce blackening of the bulb due to the evaporation of the tungsten filament. The use of this gas mixture was developed by Dr. Irving Langmuir
in 1913. (Click here to read more about the gas-filled light bulbs
.) This is the present day configuration of our standard household light bulb, which has been manufactured from 1935 onward. For further dating, if the bulb should have MAZDA, GE monogram, wattage, and voltage etched on the bulb [see A44]
, the bulb dates from 1935 to 1945 (when the MAZDA trademark was discontinued). If the bulb has the GE monogram, wattage and/or voltage etched on top of bulb but WITHOUT the MAZDA trademark, which was discontinued in 1945, the bulb dates from 1945 onward. (Click here to read more about the inefficiency of today’s standard light bulbs
A few years after Dr. William D. Coolidge’s work on the ductile-tungsten filament, in 1913, another famous Schenectady General Electric scientist by the name of Dr. Irving Langmuir (1881 – 1957) [see A49]
took the ductile-tungsten filament lamp one step further and developed the nitrogen and argon gas-filled tungsten filament lamp in order to reduce blackening of the bulb due to the evaporation of the tungsten filament. Previously light bulbs with carbon or tungsten filaments lamps were made with a vacuum (gas-free) bulb. But the presence of a pure or near pure vacuum in a glowing light bulb allowed a carbon or tungsten filament to give off or evaporate bits of the filament (otherwise called “soot”). These particles of the filament would settle onto the interior surface of the bulb thereby darkening the bulb and reducing its light output as well as its useful life span. The introduction of an argon/nitrogen gas at a pressure of slightly less than 1 atmosphere greatly inhibited this evaporation, thereby prolonging the useful life of the bulb. (See A13 for an example of a light bulb whose interior surface had been darkened by the deposition of soot from the filament
.) The ductile tungsten filament lamps shown above were manufactured from 1919 onward (as tip-less bulbs).
The present day common 60-watt light bulb has changed little since then. Compare this present day gas-filled coiled tungsten filament light bulb with Edison’s vacuum carbon filament light bulb made from the 1880s to the early 1900s. You can see that today’s light bulb, though based on some of the same principles of electricity, is far different from Edison’s. Today’s modern 60-watt incandescent light bulb has a rating of 15 lumens per watt, giving off a bright, white light compared to Edison’s early light bulb, which gave off a dim, yellowish light at 1.4 to 3.3 lumens per watt. Edison’s early lamps, manufactured before the early 1900s, did not give off much more light than that of a standard candle, which gives off one lumen. But they were more convenient (and safer) to operate than a candle or oil lamp and thus proved to be very popular. However, even though today’s standard household light bulb may be more efficient than Edison’s early light bulbs, as well as economical and popular, they are still to this day very
inefficient overall and have not been much improved on since this double-coiled tungsten filament gas-filled light bulb came out in 1935. About 95% of the energy given off by almost any incandescent light bulb is in the form of infrared light, or heat, while the rest (5%) is emitted as visible light.
NEXT PAGE in the Evolution of Incandescent Light Bulbs