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

Re: gum "curves"

Just as a person who is currently experimenting with curves for my
gum-over-cyanotypes, my take on this debate is that the most powerful use of
Mark's curves system is for printing methods (such as platinum and
cyanotype) where post-printing manipulation is not really possible. In those
cases you can take an original with a full range of tones, and using your
own chosen processes (printer, negative substrate, exposure device, paper
etc etc) produce a digital negative which will make a full-range print with
good separation right across the tonal range, and no test strips needed.
I've done it with cyanotype and it worked just fine right off the board.

With gum you have a choice, and I guess it depends on personality type and
your approach to the art. Because you have so much post-exposure control
with gum, you can "manage" your print right through until it's dry and even
beyond. On the other hand, if you prefer to put the effort in earlier in the
process and then have a result that is predictable with the minimum of
hands-on manipulation, then you'd probably think that the effort involved in
analysing your workflow and materials, generating curves (it's not very
hard) and then keeping everything as constant as you can, is well justified.

(Of course, I appreciate that the words "gum" and "constant" are not often
found in the same sentence... In the lab we used to call it TMV - Too Many

I seem to recall Robert Pirsig exploring the difference between what he
called "classical" and "romantic" mindsets in Zen and the Art of Motorcycle
Maintenance. I suspect that that's the underlying debate here.

Best wishes


On 27/10/06 17:32, "Katharine Thayer" <kthayer@pacifier.com> wrote:

> 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