From: Joe Smigiel (jsmigiel@kvcc.edu)
Date: 07/13/03-07:51:08 PM Z
Sandy,
I usually print around 8x10 and to maintain even illumination the 1000w FEL lamp is about 6 feet away from the contact frame. The lamp is in the DP light housing which can be focused to minimize hot spots. Exposures range from about 6 to 10 minutes using various pigments, saturated potassium dichromate and a gum:sensitizer ratio of ~2:1.
As far as the UV tubes, I think they are fine for other alt processes, but they are not consistent IME for printing gum. I can't repeat results from one print to the next using the same emulsion, paper, etc during the same printing session. (Maybe there is some sort of voltage flux affecting the lamps but I've found the FEL works better so why continue to print gum with the UV tubes?) I don't have those problems with the quartz lamp. The exposures are a bit longer since I have to back the lamp away to get even illumination but that's OK especially when I'm running a bunch of prints. I run out of tray space for development quickly so a little longer exposure time really doesn't matter.
I know others will disagree, but I believe the quartz lamps, regular incandescent photofloods, and good ole Sol are much better sources for printing gum. I recently acquired a NuArc plateburner with a mercury lamp but haven't run any gum through it...works great for vdb and I suspect other processes.
Joe
>>> sanking@clemson.edu 07/13/03 20:34 PM >>>
Joe,
I looked at the spectral power distribution of the quartz halogen
lamps and what I saw suggested there was very little UV radiation,
and my logical conclusion was that the lamp would be less efficient
than other lamps for printing with UV processes. Since you are using
the the lamp for gum printing I was obviously mistaken. But please
describe the set-up you are using in terms of wattage of lamp,
distance from printing frame, how much area is covered evenly, and
your basic printing times with whatever type of negative you are
using.
As for the UV fluorescent tubes causing fog, I don't think so. I
certainly get no fog with either carbon, kallitype or palladium
printing, or for that matter with the little gum I do, and the output
is very, very consistent. In fact, I am using my UV bank of tubes
without a light integrator and the resulting prints are just
absolutely dead-on identical, at both short and long exposures.
Sandy King
>Sandy,
>
>I have successfully used a quartz halogen FEL 1000w lamp for gum
>printing. In fact, I prefer it over UV fluorescent tubes since I
>believe the latter cause fog and are less predictable in output than
>the FEL. The FEL lamp is standard in the Lowell DP photo studio
>light and can be purchased from a number of bulb suppliers as well
>as mail-order photo suppliers like Calumet. The cost is somewhere
>around $16 for the lamp.
>
>iWhy do you state the quartz halogen lamps "would not work for your
>needs" in gum printing ?
>
>Joe
>
>>>> sanking@clemson.edu 07/13/03 15:53 PM >>>
>Sarah,
>
>There are many kind of quartz lamps, including halogen which would
>not work for your needs. There is an Ultraviolet quart lamp that is
>used in medical therapy. One place that handles this type of lamp is
>Baar Products, at 1-610-873-4591. You can find other sources with a
>Google search.
>
>Be very sure that you understand the potential dangers in using a
>lamp of this type. Most of the UV lamps that we use for exposing UV
>processes (HID lamps such as mercury vapor and metal halide, BL, BLB,
>and SA fluorescent tubes) put out most of their radiation in the
>Ultraviolet A zone, which is not especially hazardous to your health.
>I have not seen a spectral intensity chart for the medical therapy
>lamps but if they put out a lot of UV in the range below 300
>nanometers I would advise against their use.
>
>There is an article on UV light sources for alternative processes
>that you can see at http://unblinkingeye.com. However, I did not do
>any research on UV quartz lights because at the time I did not know
>that this type of lamp was being used to expose UV processes.
>
>
>
>
>Sandy King
>
>
>
>
>
>>Hello,
>>
>>I want to start with gum printing and I'd like to ask if anyone has
>>an idea from
>>where I can buy or order a 1000 W quartz lamp (in the USA).
>>
>>Thanks a lot,
>>
>>Sarah
>>
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