Re: pigments for gum and PDN

Chris,

I'm making slow progress but so far my observations may back you up
somewhat (but not entirely) on the idea of different curves for
different pigments. I found that starting with the same curve and same
exposure time (2 minutes) for all, the reds and yellows that I have done
have developed in 20 minutes and similarly well-stepped, although I
don't have enough data to say definitely that I don't see a difference
between reds and yellows. But I do see a definite difference between the
reds-yellows and the blue (I'm only using pthalo so far to simplify
comparisons between reds and between yellows). With the pthalo, I
haven't been able to get the two darkest "steps" to differentiate, even
with 2-day development. No doubt a curve that adds more negative density
for the shadows could help that. (I tried cutting exposure to 1.5
minutes but that was underexposed; I lost the lightest "step" in about 5
minutes of development.)

But my sense is also that there's too much pthalo in the pthalo. I
wouldn't have thought til this week that you could get too much color
without staining, but now I'm thinking that it is so (based on not only
this but on the way the colors work on top of each other). This is more
pthalo than I would ordinarily use with my intuitive-by-eye mixing
method, but I was trying to standardize the colors as much as possible
by using each color absolutely as saturated as I could get it (I've done
this by putting more color into the gum, printing, putting more color
in, printing, til I didn't see any difference in the depth of the
printed color between two printings).

Which brings me to recall Dave Rose's comment of a while back: why are
we messing around with paints, when dry pigment would be so much easier
to standardize? While I think these experiments are useful at the stage
where we are now, (any data are better than no data) I think eventually
they must be redone with dry pigment in order to be able to draw any
general conclusions from them.

I am still trying to get my mind around how different curves for
different pigments would work for tricolor, so am anxious to see what
you discover in the end. I can see how if the pigment/gum ratio is too
high, a curve that adds more density in the shadows could help hold
back some of that excess color, as with my example with pthalo above, so
that the darkest gradatiions will develop more quickly. But if the
pigment/gum ratio was too low, I don't see how a curve could help with
that. And if one was using a weak or unsaturated pigment that couldn't
hold its own with the other colors, I don't quite see how a curve could
help that either. But I'm open to persuasion with data, of course.

> I've finished the cyano coats (Fab Artistico Traditional White Cold Press
> ONLY because I have run out of AEW hot pressed sized paper)

Sorry, what's AEW paper?

Katharine

and found one
> thing for sure--this paper requires a 15 minute exposure instead of a
> comparable 6 minute exposure on Platine, and Platine is a more gorgeous
> thalo. Side by side, the PDN curve wins over my old curve. First layer
> only, though and two more to go.

K
> Chris
> ----- Original Message -----
> From: "Kees Brandenburg" <ctb@zeelandnet.nl>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Saturday, June 11, 2005 6:12 AM
> Subject: Re: pigments for gum and PDN
>
> > Hello Chris
> > Did you make your curves from a one coat gumprint? As the tonal range
> > gets longer with more coats curves might be more accurate when measured
> > and calculated after more than one coat (i.e. with your usual/preferred
> > number of coats). Never tried it though.
> >
> > At what point do the curves for the individual colors differ?
> >
> > -kees
> >
> >> Today I print a side by side gum my old way (one curve for all three
> >> layers, black ink only neg on Photo Warehouse film)and then with all
> >> three layers done with their own color and curves (PDN method, colorized
> >> negs with 3 separate curves and 3 separate printing times, no black ink,
> >> Pictorico film), to see if there is a benefit with gum this way or not.
> >> I have no clue. I am going to predict that gum is such a variable
> >> process that it does not matter, being able to take care of these
> >> variables through development and by eye, but I'd love to be proven
> >> wrong. I know with cyano, silver, palladium and solarplate the PDN
> >> system works like a charm. I also know that at the least I have learned
> >> lots more about how gum and color respond by doing it.
> >
> >
> >
Received on Sat Jun 11 10:59:39 2005