From: Richard Sullivan FRPS (richsul@earthlink.net)
Date: 09/29/01-11:45:00 AM Z
Packing UV tubes close together does increase the out some but not as much
as one would expect. A good trick is to make a double bank. You'll need to
use the ballasts and stand-offs for the bulbs but in effect what you do is
use both sides of the light bank. Build a holder for your print frame and
you can print on top of the bank as well as on the bottom. Of course unless
you do both prints the same exposure you will need to do what I called
managed printing. That is the light bank stays on and you remove the print
from the light when it is cooled.
I had a bank like this in California that I bring with me to New Mexico. (I
took out the light unit and never rebuilt it.) It was a work bench with a
glass top and tubes ran underneath the top. There was also a shelf
underneath the tubes. I could print on top or on the shelf underneath. As
you can see, if the tubes are close together all the light coming from the
upper portion of the tubes is lost in a one sided system. Most people do
not concern themselves with printing on this scale but if you are printing
a portfolio for sale as I did in the late 70's (Harry Smith San Francisco
c. 1906) then you are looking for production capability. I was jumping
around like puppy dog in a room full of rubber balls - coating, printing,
washing and drying. You can for production make up for print speed by
having print space in some cases, specifically where you need to print
different negs but if you want to make 25 prints of the same neg then the
difference between a 1 hr exposure and a 10 minute exposure is significant.
Some points:
Flat bight clean white is more reflective than shiny aluminum or any other
metal including a mirror. Use a base white paint, the one they use to add
color to for room walls.
A fl tube bank is only a point source when the bank is far enough away to
look like a point. In other words at close distances, say for a 2 ft x 4 ft
bank, for anything less than 16 inches, the distance from the bulbs is
insignificant. At 10 inches or 6 inches or 2 inches doesn't matter much.
With a good white reflector behind the tubes you can space them about 1
tube apart and get about a 30% loss of light.
Semi collimated lights with a reflector give more "luminous" prints,
especially with thick emulsion processes like carbon and gum, or POP. This
is due to the image being projected from one direction of light rather than
scattered light.
So if possible forget fluorescents. If you are serious and have the space
go with a industrial metal halide light like Sandy built, it's cheaper,
easier to build, faster in print speed and some would argue gives a better
print.
--Dick Sullivan
At 08:26 AM 9/29/2001 -0500, you wrote:
>Not at all. At least none that I can perceive. I'm using a fluorescent
>tube bank, four inches from the glass, so light is flooding into the glass
>from all directions. Any minute distortions would be averaged out, I would
>think.
>
>A while back, when I was having problems with the lights "coming on",
>someone suggested aluminum foil be placed under the light fixtures, to which
>someone else warned about the problem of errant reflections and hot spots.
>As a crude test, I developed a sheet of paper that I had evenly coated with
>kallitype sensitizer, and used the heavy glass. Exposed for a middle gray,
>I saw no problems with evenness of lighting. I did catch some problems in
>my coating procedure, though...
>
>-----Original Message-----
>From: Judy Seigel [mailto:jseigel@panix.com]
>Sent: Saturday, September 29, 2001 2:13 AM
>To: alt-photo-process-l@sask.usask.ca
>Subject: RE: UV light and Contact Frame
>
>
>
>
>On Fri, 28 Sep 2001, Keith Gerling wrote:
>
> > All of my printing of late has been on 22x30 inch paper. I use a 28x28
>inch
> > piece of "coffee table" glass that is almost a half inch thick, and
>beveled
> > on the edges. Incredibly heavy and awkward, it takes a bit of practiced
> > coordination to move it around, but it seems to do a good job of holding
>the
> > negative flat. I use a piece of carpeting underneath the print. One
>thing
> > is for sure: you won't need to worry about weights or rubber bands. I
> > bought this glass at a place called "Hobby Lobby" that specializes in silk
> > flowers and other weird, kitschy items. They also sell beeswax and
>paraffin
> > at prices far less than other stores.
>
>Keith, I realize this may be just superstition -- but doesn't the very
>thick glass have some kind of distorting effect?
>
>Judy
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