I want to know the answer to the following question:
When was the tungsten filament introduced?
All the background I'm provided with is that "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.". Is that enough to answer the question?