Re: Building UV exposure unit (was Re: new to list)

On Wed, 3 Nov 2004, Sandy King wrote:

> I disagree with Dave about the need for a ventilation fan. Even with the
> ballast mounted outside of the exposure unit the temperature of the tubes
> will build up to close to 100 degrees with long exposures, and at that
> temperature their output will decrease by up to 50% or less than the output
> at 70 degrees F. I have verified this with a light integrator which actually
> measures light output. One might be able to get away without the fan if your
> exposures are ten minutes or less but for consistent results with processes
> that do not allow much control in development I would definitely recommend a
> ventilation fan.

It's true that my exposures are generally short -- and I don't do such
precision exposure for gum anyway as might be required for the less
flexible processes... but still, the tests I have done and general
experience tell me that the construction of the light box is a critical
variable in this: Mine is open on 3 sides, that is the ends are not
solid, but open framed. I haven't found evidence of heat buildup, and
do not use a fan.

Also, reading the previous thread about the need to ground the lights or
not, if I didn't know what you were talking about it wouldn't have become
clear, actually it isn't clear yet: But my experience is that if you buy
the complete units (ie, the fluorescent bulb(s) with starter, ballast,
base, and wire already put together), they are already grounded. No need
to add a plate, a wire, or a hex sign. It's cheaper if you get the
two-bulb fixtures, which may or may not be available in the length you
want.

But it's even cheaper (tho not by as much as it should be) to buy the
bulbs, ballasts, end pins, & wire separately and assemble. Then you need
to add a ground, and probably strong language at appropriate intervals.

Judy
Received on Wed Nov 3 23:01:24 2004