From: Joe Smigiel (jsmigiel@kvcc.edu)
Date: 07/13/03-08:50:58 PM Z
Sandy,
I think a lot of folks have trouble printing gum and the fogging problem with UV tubes may not be restricted to just my experience. But, instead of advising people to change the UV source, people are usually directed to alter the size or paper or sensitizer ratio, etc., when maybe, just maybe, the UV tubes are not the best choice for gum printing. I've made good prints with the UV tubes, but in my experience the exposures are not consistent print to print and this weird fogging problem crops up once in awhile.
The standard advice in most books on gum printing is to use Knox gelatin for size, Rives BFK paper, Winsor & Newton Alizarin Crimson, Cad. Yellow, Winsor Blue (pthalocyanine blue) and Lampblack pigment with 14B gum and to measure tube pigments by the inch and expose using UV tubes. Well, I have never been able to make a print with Winsor Blue that didn't stain. (Others apparently have.) Winsor Blue is a beautiful transparent blue but one of the most staining pigments you can buy. I've made some good prints on Rives BFK, but find other papers are better for my methods. Cad. Yellow is opaque and to me, a poor choice for gum printing. Alizarin is another stainer and apparently a bit fugitive. Knox is soft and higher bloom ossein works better for me. I also think ammonium dichromate is more prone to fogging than potassium. And the Andersen pigment stain test...well just check the archives for that one.
My point is that the light source has never been considered as a potential problem in gum printing. I don't know why the UV tubes give me a problem once in awhile, but I've pinned down my fogging problems with gum printing to the light source and made an adjustment which has eliminated the fogging. I'd suggest that others might try the same if fogging problems occur.
Several years ago on the Bostick & Sullivan bulletin board the issue of light sources for printing gum did come up. Several people reported much improved results simply from switching from UV tubes. Several people switched to quartz lamps at that time, including myself. We just didn't hear much about it on this list.
Joe
>>> sanking@clemson.edu 07/13/03 22:14 PM >>>
Joe,
If the quartz halogen lamp works better for you than UV tubes, great.
Other folks on the list may want to experiment with this lamp since
it is really dirt cheap compared to virtually all other UV light
sources.
As for the consistency of UV tubes your experience is just vastly
different form mine. However, I have to belive that if there really
were a generic problem of consistency with UV tubes in printing gum
(as opposed to your particular problem) a bunch of other people would
have noticed and commented on it since the tubes are so widely used.
Sandy
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