U of S | Mailing List Archive | alt-photo-process-l | Re: gum "curves"

Re: gum "curves"

On Oct 26, 2006, at 8:42 PM, Judy Seigel wrote:

I also suspect that Katharine is right -- that every change of pigment, and mix, every new batch of sensitizer (they tend to lose speed as they age), every new purchase of gum (which changes drastically from maker to maker, and also season to season) every new tube of paint (they've been known to perform differently, even when officially the same) AND every MIXED color (which would surely change the "curve") would require a new curved negative. AND if you decide to avoid such changes as far as possible to keep your nicely curved negs viable, you will be, as far as gum printing is concerned, tying one hand plus 3 fingers behind your back.
I didn't just make that up out of thin air, that's been my understanding from the "curves" contingent all along, that a curve is specific to a particular set of printing conditions, including emulsion, paper, equipment, and environmental conditions (and a particular inkjet printer) and to use the system properly you need to make a new curve every time you change any part of that equation. I remember one discussion where I was arguing that I get perfectly good results using the same curve (no curve) and adjusting the exposure for different pigment mixes and conditions, and wondered if just printing the same curve with different exposures might achieve the same end (in the print) as printing different curves with the same exposure. I was told that holding the curve constant and changing the exposure doesn't yield the same results at all as holding the exposure constant and making different curves for each pigment, the implication being that doing the latter gives such superior results that if you're not doing it that way, you're just not really up to speed with gum printing (although as I keep saying, surely if this were true, the gum prints coming out of this system would be so superior to gum prints ever made heretofore, that it would be apparent to all... frankly I just haven't seen it). Since I hadn't done that comparison myself, I couldn't argue with the assertion. And recently someone was telling us that the thing about the currently fashionable curves system that makes it superior to all others is that it is geared precisely to the conditions and materials of one's specific situation.

I don't know how it could be otherwise, since the curve is generated for a specific printing protocol, and as we all know, different conditions, different materials, different equipment, different pigment mixes, etc, require different printing protocols.