Expert: Henry Boyter - 7/21/2004

Question
Still confused.  Your links discuss Mercury lamps and fluorescent lamps, when what I wondered about was incandescent lighting.

Mercury lamps require phosphors because a significant percentage of their light is emitted in the ultraviolet range, which the phosphors absorb and re-emit at a longer wavelength.

Incandescent bulbs, however, emit a full spectrum of light that is shifted toward the red end of the spectrum, owing to the relatively low temperatures achieved.  (The sun, by contrast, since it burns much hotter, appears more yellow or even white, and very hot stars emit bluish light.)

It would seem that incandescents do not require phosphors, and that the internal frosting is designed merely to reduce the glare from the filament.  Would phosphor still be used?
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Followup To
Question -
Everyone knows fluorescent lights are frosted with phosphor, which "fluoresces" in response to the energy discharged by the gases within the tube.  What no one seems to know or mention is what the white powder within frosted incandescent bulbs is.  I know the original frosted bulbs were etched, but I broke open a GE "Watt-Miser" bulb recently, and it definitely contained a white powder coating on its internal surface.  What is it?
Answer -
It will be a mixture depending on age and manufacturer.
Some links found using google.com.

http://www.lamptech.co.uk/Documents/M14%20Phosphors.htm

http://en.wikipedia.org/wiki/Fluorescent_lamp

Answer
Sorry I confused what your question was asking.  Incandescent bulbs were normally etched while some new ones have glass containing niobium (or other rare earths) that make the glass appear frosted. The etched ones will have a frosting of glass left from the etching.  GE uses kaolin (white clay) on the inside.

http://www.gelighting.com/na/downloads/lmi_sheet5.pdf

http://www.gelighting.com/na/downloads/lmi_sheet3.pdf


http://216.239.41.104/search?q=cache:lMewB_9VGe8J:www.chihuly.com/pressroom/pdfs

http://www.eurochristmas.com/geninfo/glass.htm