Re: "blacklight" tubes and light sources in general

The lore is that fluorescent bulbs keep glowing/emitting long after they've
been turned off. I have a fluorescent fixture in my darkroom which I shutoff
at least 10-20 minutes prior to working on any film. Could the fogging be
caused by leaving the contact frame in the UV box and going for coffee?

----- Original Message -----
From: "Joe Smigiel" <jsmigiel@kvcc.edu>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Monday, February 14, 2005 6:31 AM
Subject: Re: "blacklight" tubes and light sources in general

> Otherwise mind-boggling, inexplicable, random fogging from one gum print
> to the next. I've never had a fogged gum print since I made the switch
> to a quartz halogen FEL lamp (and more recently, a mercury lamp in the
> NuArc). Before, maybe 1 out of 8 prints would become inexplicably
> fogged, frustratingly perhaps at the third or fourth or Nth or final
> layer.
>
> In contrast to your experience, I don't believe the output of the (my)
> tubes is constant nor predictable.
>
> This observation of random fogging with UV tubes has been observed by
> others including Stephen Livick and a few other individuals I have been
> in contact with the past several years. Although I can't explain the
> observation other than speculating about a nonconstant output, I repeat
> that I have never lost a gum print to fogging or overexposure since I
> switched lamp types so I've never looked back. Switching lamps abruptly
> eliminated fogging for me.
>
> Of course, I've dropped a few fragile wet prints or made some water drop
> craters in the emulsion to compensate.
>
> Joe
>
> >>> zphoto@bellsouth.net 02/14/05 12:20 AM >>>
> all my hundreds of gum prints are printed with UVBL (Edwards light
> box)...5
> minute exposures, perfect, predictable....but I do use only a 7% am di
> in my
> mix. What doesn't work for you, Joe?
> Chris
>
> > You don't say for which process(es) you intend to use the UV source.
> > IME, UV fluorescents basically suck as an exposure source for gum
> > bichromate but are fine for other processes. I would recomend a
> quartz
> > halogen, metal halide, or photoflood for printing gum.
>
>
>
Received on Mon Feb 14 09:42:46 2005