Re: gum "curves"

[Katharine Thayer <kthayer@pacifier.com>]

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.



Katharine