From: John De Armond
Newsgroups: sci.engr.lighting,sci.engr.heat-vent-ac
Subject: Re: ozone generating lights
Message-ID: <qo3u7u47gv7uiad0h0o3j58ke3o79gd1c5@4ax.com>
Date: Fri, 01 Mar 2002 00:24:01 -0500

On Tue, 26 Feb 2002 09:20:02 +0200, Ioannis <morpheus@olympus.mons>
wrote:

>lopi wrote:

>You could also use the following, although WARNING! it's NOT recommended
>and it's dangerous!!!
>
>Use the quartz tube from a regular 80-400W HID mercury bulb, but INSTEAD
>of connecting it in series with its appropriate inductive resistance,
>connect it in series with a 30-50 KOhm regular resistance. Under those
>circumstances, the quartz tube will operate in glow discharge mode, so
>the visible light will be minute, but a considerable amount of
>ultraviolet radiation will be generated, enough to fulfill some of your
>needs. But be VERY careful, even this little UV can badly burn your eyes
>and skin before you can take notice.

An even better solution is to get a low voltage neon sign transformer,
say a 3500 volt, 20 ma unit and drive that quartz tube with it.  These
little transformers are cheap - about $25 - and won't waste power or
make lots of heat like the resistive solution.  Plus the tube will
always light.

I use just such a setup to cure UV epoxy in my glass shop.  Works
great.

One little correction - this setup makes a LOT of shortwave UV.  Most
folks know about the eye hazard but most don't know just how quickly
the ozone produced on the surface of objects illuminated with this
stuff will damage things.  One can bleach the color out of fabric in
hours.  Ditto for dye-based ink.  Many plastics will turn brown within
a day from surface oxidation.  this means that the tube should be
operated inside a metal enclosure that blocks the emitted light.  Just
blow air through the enclosure to produce the ozone.

john

From: John De Armond
Newsgroups: misc.rural
Subject: Re: Yard Light goes off several times during the night.
Date: Thu, 02 Mar 2006 15:51:11 -0500
Message-ID: <mfle029ak9j2m41ojpf8fe5evobjdp3128@4ax.com>

Nope.  Both metal halide and mercury vapor bulbs from both major
manufacturers are made of pyrex.  It will NOT crack upon water
exposure.  The composition is stated in the fine print.  I'm
intimately familiar with the glass because I blow the bulbs from old
lamps into art objects and then pump 'em with neon to make 'em glow.
Pyrex and soda lime glass are two totally different critters.

Additionally, the UV exposure from the bare tube is grossly overhyped.
The quartz used in modern lamps has a cutoff above the very damaging
UVC rays.  There is a relatively low amount of UVA and UVB in the
output.  This is so-called "no ozone" quartz.  UVC is very damaging to
the phosphor coating (the white stuff is actually a phosphorus that
glows bright pink under UVB.) and contributes little to the light
output so it is filtered out.  UVC also solarizes pyrex (turns it
dark), a quite undesirable feature.

I originally became aware of this from two events.  The first event
was my making a "high power curing lamp" from the arc tube of a MV
lamp.  I wanted to set UV-cured optical cement faster than my
germicidal lamp would.  No good.  The cement needed the short wave
emission at about 285nm to cure.  The "no ozone" quartz envelope
stopped almost all the UVC light.  It was slower than the 12 watt
germicidal lamp which is an ordinary fluorescent lamp made with a
glass that passes UVC in order to make ozone.

Around the same time I made my ex a 'tanning lamp' from two 400 watt
MV arc tubes mounted in 500 watt halogen reflector fixtures.  I
reasoned that since the "no ozone" quartz was spec'ed to pass UVB, it
would make a good tanning lamp.  No go.  She spent a couple of hours
under these lights with no results (I was quite happy, as I didn't
want her tanning with her family's history with cancer.)

Only THEN did I bother to do what I should have done in the beginning,
looked at the output with a UV spectrometer.  And some research on the
net.  It turns out that a HIGH PRESSURE MV arc produces little
activity above UVA.  The quartz passed whatever was emitted, there
just wasn't much.  I later covered one of the fixtures with "BLB"
glass, that black glass used in black light lamps and got no more
fluorescent response from fluorescent paint than from an 18" black
light.

I did run one of the arc tubes from a fluorescent lamp ballast (low
temperature and pressure) and DID get a rich spectrum but the
intensity was no more than from a germicidal lamp of the same length
and diameter.

I've read some accounts that I tend to believe involving people being
sunburned from large MH lamps.  I imagine the lamps were some sort of
cheap knockoff products (one was with a school district - think "low
bid") that didn't use the "no ozone" quartz.  I know for a fact that
the major brands all contain the "no ozone" quartz.

Since every electrical supply house I've dealt with, every sign supply
company I've dealt with and all the big box stores only carry brand
name lamps, I suspect the chance of running into a knockoff out in the
wild is slim to none.

John

On Thu, 02 Mar 2006 03:01:16 -0800, Don Bruder <dakidd@sonic.net>
wrote:

>In article <usfd02lfahrpsii0ei6olm699uv3la57j9@4ax.com>,
> maradcliff@UNLISTED.com wrote:
>
>
>> BTW: From what I can see from the ground, the bulb is not cracked.
>> There's no reason it should be anyhow, there is a plastic shell around
>> it and no tree branches or anything to hit it.
>
>Ground-observations mean little or nothing - All it takes to virtually
>guarantee a cracked bulb is a single drop of water hitting it while it's
>hot - frost on the inside of the shield melting and forming a drop, the
>wind lofting a snowflake or raindrop against it, or any other mechanism
>you care to dream up for getting it there, and you've got a bulb that's
>spewing UV at you.