1911

Later research by a General Electric scientist led to the development of drawn or ductile tungsten filaments.  This tungsten filament, unlike its non-ductile tungsten predecessor, was malleable and ductile under room temperature and thus could be drawn in a very long strand several feet in length without breaking.  This metallic looking filament could then be mounted and threaded or strung between two levels of several supports with hooks attached radially around the upper and lower portions of the button rod.  The ductile tungsten filament was developed by the famed Schenectady General Electric scientist Dr. William D. Coolidge (1873 to 1975).   Because tungsten in nature is such a brittle, delicate material that broke easily at room temperature, it was believed by many scientists that tungsten could never be made ductile (or, in other words, plastic or malleable) and strong at room temperature [see A27].  But the industrious Dr. Coolidge thought otherwise and actually spent a good number of years (from 1905 to 1910) working hard and diligently to accomplish the seemingly impossible.  Throughout those five years, he performed a large number of experiments with tungsten by combining them with other materials and then selectively hammering, rolling, drawing and heat-treating the combined metals at various temperatures before allowing them to cool down to room temperature and then testing them to determine which of them would retain their hardness.  His persistence ultimately paid off.  In the end, he found that the repetitive heating and hot swaging of tungsten and then drawing it out through a die and allowed it to cool would allow it to retain its malleability at room temperature.  He had created a hard but ductile filament that, at room temperature, could be shaped in any form, and more importantly, at any desired length without breaking.  Another milestone in the history of lighting was finally achieved.  Lamps with these ductile filaments were very bright, lasted longer than any other previous lamps, and could withstand rough handling while mounted in any position.  Thus Dr. Coolidge, born before Edison’s first successful lamp, had set into motion the last chain of developments that lead to today’s modern, economical and popular incandescent household light bulb.  He lived to see the widespread use of incandescent lighting before he died at the age of 101 in 1975.

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