Context: In 1906, the tungsten filament was introduced. Tungsten metal was initially not available in a form that allowed it to be drawn into fine wires. Filaments made from sintered tungsten powder were quite fragile. By 1910, a process was developed by William D. Coolidge at General Electric for production of a ductile form of tungsten. The process required pressing tungsten powder into bars, then several steps of sintering, swaging, and then wire drawing. It was found that very pure tungsten formed filaments that sagged in use, and that a very small "doping" treatment with potassium, silicon, and aluminium oxides at the level of a few hundred parts per million greatly improved the life and durability of the tungsten filaments.

Question: When was the tungsten filament introduced?
Answer: 1906

Question: What was the problem with manufacturing the tungsten filament?
Answer: Tungsten metal was initially not available in a form that allowed it to be drawn into fine wires.

Question: Who developed the ductile form of tungsten?
Answer: William D. Coolidge

Question: When was the ductile form of tungsten invented?
Answer: 1910

Question: What other materials were combined with tungsten?
Answer: potassium, silicon, and aluminium oxides

Question: What was introduced in 1900?
Answer: Unanswerable

Question: What was initially available in a form that allowed it to drawn into fine wires?
Answer: Unanswerable

Question: What made filaments quite strong?
Answer: Unanswerable

Question: Who did not develop the ductile form of tungsten?
Answer: Unanswerable

Question: Where was William D. Coolidge employed in 1902?
Answer: Unanswerable