gum curves

Hi all,
Gees--subject line sounds like a sex spam for an old folks home..

This weekend I was a curve maniac. Anything to divert myself away from a
nude powerpoint with 265 slides to input and organize.

A number of months ago I was working out gum curves and then I had to move
from the South. That work just got resumed this weekend. I was testing,
doing all my curve work with Nelson's PDN system, to see if, with gum, the
colorized neg makes any difference over black ink only negs. In the past I
always used the PhotoWarehouse OHP at about 1/3 or even less the cost of
Pictorico, and that accepts black ink well, but color puddles. Hence,
monetarily I would much prefer to stick with PWOHP.

One other problem I have with Pictorico aside from cost: it is such a
thick base that it is the only substrate i have ever had problems with not
being in contact with my paper and producing fuzzy spots. The PWOHP is so
flimsy (and stretches, sometimes, in the printer) that it remains closely in
contact with my paper in a contact printing frame. I do not have a vacuum
easel :(. So if there are any waves in the paper from moisture or what have
you, you have to watch this.

Consistently I have found this: magenta and yellow and cyanotype all have
different curves with both black ink only and with colorized inks. So I can
pretty much say with surety that I will, upon splitting my channels for my
tricolors, curve each individual color's neg separately. That's the charm
of the PDN system is its ability to make custom curves--i did 6 over the
weekend.

I need mention that PDN was not designed to use black ink only so I am
bastardizing Nelson's system (sorry, Mark)...but I figured that I needed to
find correct curves for the black ink only negs, too, to give an honest
comparison.

I think I may say, too, that, oddly enough, each color's curve in black ink
and in a colorized neg is similar in shape, but maybe not the same. I have
no idea what this means. But cyanotype is very responsive to black ink
only, in fact, probably too much so. And, the curve shape is similar with
each color within the pigment family, e.g. cad yellow and a transparent
yellow

Today i begin printing side by sides of colorized and black negs, but it'll
take a couple weeks to finish and post results.

I still am planning on testing Lehman's hydroquinone hardener, but that'll
be when I run out of my current batch of sized paper.

Bob, so nice that you posted the stuff about grainy cyano--I have had that
at times, too, for some unknown reason.

Oh, it's a monday!
Chris

PS OHHH question, how do you deal with the areas of midtone sky that print
out in uneven strips of density--what is that called??
Received on Mon Nov 7 08:32:55 2005