Grey matter
Question: The surfaces of the incandescent light bulbs where I work become
progressively greyer over time. Why?
Answer: The greying of the inner surfaces of incandescent bulbs is the result
of gradual evaporation of tungsten from the filament while the light is on. This
evaporation eventually makes the filament so thin it burns out.
Various methods have been developed to reduce greying. Filaments of the first
incandescent lamps burnt in a vacuum, but it was soon found that introducing
inert gas to the bulb reduced the rate of greying. A mixture of nitrogen and
argon is used today.…
