re:Halogen lights and UV

[P3D Elliot Burke <elliot@xxxxxxxxxx>]

>Date: Sat, 7 Dec 1996 01:51:20 -0500
>From: P3D John W Roberts <roberts@xxxxxxxxxxxxxxxxx>
>To: photo-3d@xxxxxxxxxxxxxxx
>Subject: Halogen lights and UV
>Message-ID: <199612070651.BAA11345@xxxxxxxxxxxxxxxxx>


>I recently bought some 500W halogen work lights - they came with external
>UV shields, and a warning not to operate them with the shields not in place.
>
>I have an older halogen house lamp without a UV shield, but it points up at
>the ceiling, so illumination is entirely by reflection from the ceiling.
>
>(Additional data point - I tried to use the older lamp to cure some "UV cure"
>adhesive, but it didn't work. Maybe the adhesive requires the shorter 
>wavelength UV, though it's supposed to cure in sunlight.)
>
>John R
Most of the UV cure adhesives are sensitive around 365 nm.  Since most
sources consider visible light to end at 375 nm, this is just barely
into the UV.  I wouldn't be surprised if light filtered to pure visible
(>=375 nm) would set off the UV cure adhesives.  The inexpensive UV cure
lamps are halogen.
Perhaps if you waited a little longer your halogen lamp would have cured
the adhesive.  Did you check the adhesive in sunlight to make certain it
was still good?
Another point about material properties in UV: TiO2 is a common white
pigment, with strong UV absorbtion.  So a lamp containing UV would be
rendered safe(r) by reflection from you ceiling (if it used a flat paint
with TiO2 pigment).

specular reflections and other pigments (CaCO3 and PbO2) could throw
this off.

Elliot Burke
HighTide Instruments
elliot@xxxxxxxxxx


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