I always insisted on the 350BL wavelength because it was more
universal than most others.  Riston, kind of emulsions will
work with 375nm ok, but other emulsions like some thing more
towards 400 more towards the white end of the spectrum.

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SYLVANIA 375 Blacklight F15T8/375BL (white milky internal) (15w)
This will work with Dynachem and Riston, no problem

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AVS G15T8 GL15 Germicidal (this one is clear glass) (15w)

This  is the dangerous wavelength, about 269nm, is NOT suitable for
exposing photomechanical emulsions, good for erasing eproms.
Very DAMAGING to the eyes and skin so must be used in an enclosed case.

- - -

SYLVANIA 350 Blacklight F20T12/350BL 20w (white milky internal)

This is the best all round tube, works for almost anything.
Distance from tube to emulsion surface should be min of 2" (50mm)
and max 3" (75mm) for best exosure times.

- - -

Bulbs SHOULD be run for 15 to 20 minutes prior to beginning
exposure when bulbs have been switched off for more that 4 hours
in summer, 1 hour in winter.
This is to vaporise the mercury inside the tubes
so as to generate the Ultra Violet.

Theoretically Speaking UV Tubes should be within seconds of startup
and use, but UV Bulbs must have a 'warm up' time.

- - -

and a comment from Matthew

                                                                                                                          Hi Bob
about fluorescent tubes.
I found these NEC fluoros easier to purchase than the Sylvania ones on
your site, and they worked fine on Riston coated board after two and a
half minutes exposure, less time may work, I havn't tried it though.

Here's a link to their page
http://www.nelt.co.jp/nhe_hp/special/special.htm#bl

I got three FL15BL 's,
I would expect the other NEC blacklights and blacklight blues to work
just as well as they all emit the same peak wavelength.
With regards to the 75 watt mercury incandescent UV emitting globe I bought,
which had a purple/blue coating on the inside, it was totally useless on
Riston after 7 miutes exposure and 15 minutes warmup.
Seems like Fluoro tubes are the way to go. As you say,
avoid the germicidal lamps.  Well, thats all,
Matthew.

- - -
comment from Bob,  Matthew used 2 and a half minutes, I suspect
he was about 6" to 10" away from the Glass > Neg > Riston.
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