1880

The carbonized split Japanese bamboo filament was the next filament to be used by Thomas Edison.  They were shiny black, long flat strips with flared or enlarged ends and rectangular cross sections whose plane is more or less parallel to our line of sight when bulb is held upright.  It could be mounted in a hair-pin fashion although with care it could also be mounted with a one or more loops.   The use of Japanese bamboo filaments was the result of Thomas Edison’s never ending search for a longer-burning and more durable filament.  Thomas Edison had his team scoured the world for plant material that would make a superior filament than that of Bristol cardboard.  He finally found the plant in 1880 from a species of Japanese bamboo plant scientifically referred to as Phyllostachys bambusoides but otherwise known by its common name as “Madake.”  These bamboo plants are indigenous to the country of Japan and, aside from making excellent lamp filaments, they also make excellent fishing rods.  To produce these filaments, pieces of a single bamboo plant would be sliced lengthwise into extremely fine strips, bent to their desired hairpin or looped shapes in order to fit into the bulb, and then carbonized by first covering them with powdered carbon (to minimize the availability of oxygen) inside a crucible and then heating the crucible inside a furnace at an extremely high temperature for several hours before allowing them to cool.  During this process, the bamboo strips would turn from its initial cellulose structure to a pure carbon structure, ready to be mounted in the glass bulbs with extreme care.  However, the length of a bamboo filament was restricted as they could be no longer than the distance between the joints of the bamboo cane.  This placed an upper limit as to how bright a carbon filament light bulb could be.  Light bulbs with these filaments did not burn much brighter than did a candle but they were more convenient and safer to use in the home just the same.

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