[geeks] Metal Halide Bulbs

[Sandwich Maker]

" From: Bjorn Ramqvist <v53278 at g.haggve.se>
" 
" James Fogg wrote:
" 
" >>So I have a case of what I believe are Philips MH250-U bulbs.
" >>250W Metal Halide, 21,000 initial lumens, something along
" >>those lines. The box was sealed in a Philips HID container
" >>and as such there are twelve of these rather large, very
" >>interesting looking bulbs.
" > 
" > If you find a way to fire these be aware that the UV output is
" > frighteningly high (sunburn and eye damage).
" 
" That's why you need a protective glass in front of the bulb, as long as 
" it's the double ended version. The single ended is harmless.
" Regular window glass is OK. Only glass that don't filter UV light is 
" quartz...

there are actually lots of glass types that don't filter uv.  ordinary
window glass has a trace of iron in it; that's what makes the greenish
tint you see on edge, and that's the major thing in it that absorbs
uv.  but my grandfather - a doctor - got low-iron glass for his
children's playroom so they'd get more vitamin d, back in the '20s.
but even regular glass lets enough uv in to fade the furniture over
time.

quartz is the most common -highly-uv-transparent- glass; it's one of
the few good down to around 100nm.

i think i'd want something more aggressive than window glass to filter
the uv, but if it was absorptive like window glass it'd get #$%^&*
hot...  a dichroic mirror would reflect the uv energy back toward the
arc until it was reradiated in the visible.
________________________________________________________________________
Andrew Hay                                  the genius nature
internet rambler                            is to see what all have seen
adh at an.bradford.ma.us                       and think what none thought