Re: UV light outputs?
John Rudiak (wizard@laplaza.org)
Mon, 15 Jul 1996 22:09:00 -0600 (MDT)
>
> My business partner and I have built a UV lightbox, using commercial
> grade, uncoated blacklight florescent tubes. It works great, but
> we've been having a "discussion" about the output of the tubes. He
> feels that the tubes have a "warm-up" time and ought to be on for at
> least 5 minutes before use. I put the box on a darkroom timer, so
> that it turns on at the start and off as the time ends. Now, I don't
> have a proper light meter to measure which way is better, but I'm
> hoping that one of you gentle folk out there can tell me if there's
> any kind of a differance in our methodology? Are there surges in the
> electrical output at the start of the timer, surges that would
> negatively affect the image? Do the bulbs "warm up" over time and
> sort of "stabilize" their output, or is it fairly consistant right
> from the start?
>
I use a similar home-made exposing unit, and have noticed a whiule ago
that the first print of the morning is a little lighter (I figure about
10% relative to exposure) than subsiquent prints made during the printing
session. I have adopted the habit of turning on the exposing unit for
the first print while the paper is drying in my drying cabinet, and have
found that this is not necessary for subsiquent prints until I break for
lunch, and the unit cools down. After lunch I do the same thing for the
first print, finding it unnecessary for subsiquent prints as long as I
continue printing at a rate of an exposure every half hour. I have also
noticed that this is more important in the winter, so I believe that tube
temperature is relevant to light output.
Anyone else?
John>