'Mazda' tungsten filament bulb, ca. 1935
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The "ductile tungsten" filament, developed by William D. Collidge in about 1911, is the method still used in incandescent bulbs. Tungsten is sintered (heated and pressed) and forced through increasingly small dies, which produces a wire that is flexible, but strong. This bulb has frosted glass, a process developed in 1925 to reduce glare.