Judy Seigel (jseigel@panix.com)
Sat, 27 Nov 1999 15:44:36 -0500 (EST)
On Sat, 27 Nov 1999 FotoDave@aol.com wrote:
>
> Hi Judy, I don't know what "unitary" means in the above, but I agree
And I suppose you think I do know -- well, what I meant was that rather
than distinct layers, the difference is probably in the degree of
hardening... like you say.
> that the highlights soak away first. What happens is the hardened gum
> can still absorb water and swell given enough soaking, so in the
> highlight area we have a think layer of hardened gum, the water has to
Well we could use a few more *think* layers in life and other places,
wouldn't you say?
> soak through this and reach the unhardened layer, soften the
> unhardened layer and that got dissolved away.
>
> On the shadow, we have a relatively thick layer of hardened gum, so it takes
> a long time for the water to soak through this layer to reach the unhardened
> part, so indeed the shadow section gets developed slower.
>
> This slower rate of development with shadow gives a practical limit to
> achieving Dmax with single-coat gum.
Dave, I agree with all you've said so far (and need I add a million
congratulations !? Don't feel bad about grousing -- some people have an
AMAZING sense of entitlement!), but sentence directly above I think is not
true. With a gouache or other strong pigment AND A NEGATIVE MATCHED TO THE
SCALE OF THE MIX you can get a D-Max with one coat as dark as the pigment
will coat. Or so it has seemed to me. There are probably tradeoffs,
perhaps some flaking or staining -- can't generalize because each paper,
pigment, mix and size combination is sui generis (and I DO know what that
means, ha ha!), and it's not necessarily automatic or easy, but certainly
can be done.
> In addition, since the thicker area
> actually gets more filtering effect from the pigment, the shadow that needs
> more exposure actually gets less exposure, so gum has a long shoulder if one
> wants to include the deep deep Dmax (as Adam Kimball mentioned one time that
> he got the visually linear range but then it took 5 or 6 steps further to get
> the deepest black).
> If one coat thicks, expose a lot (I mean, A LOT, like 30 minutes or an hour),
> and soak long, one is able to get a long scale with gum (10 to 12 steps and I
> have those steps), but that includes the loooong shoulder for the shadow (I
> believe you called it "blocked up" shadows with little separation - the
> separation is there but not useful enough for tone separation).
I agree here, too -- but in my experience the really long soak CAN warp
the curve... tho not necessarily, depends again on the mix... The tendency
in my tests was for a nice long scale up to the high midtones and then
whoooops -- BIG step where the highlights washed back in the long soak.
Meanwhile, I' ve been distracted by head cold & seasonal rites, and
apologize for not having paid as close attention to your original
announcement as I should have. If this question was answered, please
excuse -- and if it's part of what's not for publication, forget I asked.
But when you call your method a *carbon* print, what is the basis for that
definition? Because it's based in gelatin rather than gum arabic?
> That's another reason why the SDC is different from standard gum. It is able
> to achieve deep matte black but with full tone.
>
> > (I would imagine
> > that the "direct carbon processes" which pop up now and again (and
> > lately!) use a thinner coat too.)
>
> Well, I don't know how thin is thin, but yes I know the direct carbon process
> that "popped up" recently uses a relatively thinner coat. ;)
This is in fact the century of pop art... and again congratulations on
that...
Judy
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| Judy Seigel, Editor >
| World Journal of Post-Factory Photography > "HOW-TO and WHY"
| info@post-factory.org >
| <http://rmp.opusis.com/postfactory/postfactory.html>
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