Re: tonal inversion and pigment loads

Katharine,

here is an idea, I think it is well known that heat by itself causes some
cross-linking to happen and say under a step tablet where the density is
high enough, exposure alone doesn't reach the gum but heat does. It could be
that heat doesn't transform the gum dichromate in the same way as does
exposed gum, in other word the two phenomenon don't "create" the same type
of molecule and the cross linking of one may have different properties then
the other or something like that.

I think I'll try the following, I'll prepare a gum dichromate in a very dark
area and expose it to heat alone but with a step tablet on top as usual.
I'll try say a 100 F for 15 minutes and devellop normally all this in the
dark at least for the first bath. We'll see what it does, to be continued...

Regards
Yves

----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Thursday, January 26, 2006 1:53 PM
Subject: Re: tonal inversion and pigment loads

> Well, I was looking for something else I couldn't find and came
> across a post from Yves that said that he got inversions with a 500W
> photoflood that went away with a 150W grow light, using the same
> exposure times. This almost seems to suggest the opposite of what's
> been suggested by others, that maybe more exposure rather than less
> causes inversions. All I can say for sure is that we don't
> understand the phenomenon of tonal inversion very well, and perhaps
> we're all like the blind men and the elephant, feeling it from a
> different angle. At any rate, my website and my opinions here are
> based solely on my own observations and experience, and I can only
> say what I've seen with my own eyes and what has worked for me. Cheers,
> Katharine
>
>
>
> On Jan 26, 2006, at 9:31 AM, Katharine Thayer wrote:
>
> > Sorry folks, this is old business, but when looking for something
> > else I stumbled across this post, which I hadn't seen before, and
> > feel it deserves a response.
> >
> > On Jan 12, 2006, at 10:10 PM, Christina Z. Anderson wrote:
> >
> >
> >>> Sure there would. If for example the the pigment overload is
> >>> sufficient to cause the emulsion to flake off, and also
> >>> sufficient to cause staining, what you end up with is a thin
> >>> layer of hardened gum (left behind when the emulsion flaked off)
> >>> that's differentially hardened; this hardened gum acts as a
> >>> resist to the pigment stain, in an incremental way.
> >>>
> >>>
> >>
> >>
> >> Then you are agreeing with Judy that exposure figures into the
> >> equation of
> >> pigment stain, correct?
> >> Chris
> >>
> >
> > At first I thought, well, to give her the benefit of the doubt,
> > maybe this was sent before I posted my prints of an overpigmented
> > coating mix printed at five different exposures, showing equal
> > stain across all exposures, which demonstrates that in my gum
> > universe at least, pigment stain is not related to exposure. But I
> > checked and found that it was actually sent two days after I
> > posted those, so I'm puzzled...
> >
> > As I've said very clearly on several occasions, and as I said in
> > the post quoted above, I do agree with both of you that exposure
> > figures into the special case of tonal inversion, in the sense
> > that to get a tonal inversion you have to have a positive image for
> > the stain to use for a resist for the pigment stain to make a
> > negative image from, and to get an image you have to have
> > exposure. But to agree with that obvious and trivial statement
> > hardly constitutes an agreement with the assertion that exposure
> > "figures into the equation" of pigment stain, and the observations
> > I posted, showing that multiplying the exposure by 2, by 4, by 6,
> > and by 8 had no effect on the staining, give me little reason to
> > sign onto that assertion.
> >
> > I haven't yet seen any credible evidence that one can eliminate
> > either pigment stain or inversion by increasing exposure, but I
> > have eliminated both of them simply by changing the gum/pigment
> > ratio. I have seen some evidence, in Tom's (I think it was Tom)
> > posted test strips, that one can move the inversion up or down the
> > step tablet by changing the exposure, but again that seems rather
> > obvious and trivial to me; of course changing the exposure alters
> > where the tones appear on the step tablet; more exposure blocks the
> > shadows and sends the meaningful tones farther up the tablet, but
> > so what? The meaningful tones are still the same tones, and the
> > pigment stain is still there; the only difference is your shadows
> > are all blocked. The crucial variable in the inversion, as far as
> > I have seen, is overpigmentation, and if the gum is overpigmented,
> > you'll either get stain or inversion or flaking or something,
> > because the extra pigment has to go somewhere, and the way to fix
> > it is not to expose more, but to reduce the pigment, in my
> > experience. (It should be clear from the test prints that I posted
> > that reducing the pigment enough to eliminate the stain does not
> > mean giving up printing with a fully saturated pigment).
> >
> > One caveat: I did see an oddball thing where someone sent me an
> > inversion he got with a very small amount of pigment; he then got a
> > positive image with the same pigment mix by exposing more, but at
> > the same time he increased the exposure, he changed other
> > variables as well, so it's impossible to say what caused the
> > improvement. Which is why you should never change more than one
> > thing at a time.... at any rate, he was using blue photofloods for
> > the exposure and my experience with them suggests they don't behave
> > like normal lights do. So that one seems like an anomaly to me,
> > unexplained and unexplainable without further investigation, one
> > variable at a time. When someone can show me an inversion with a
> > light pigment load that goes away with increased exposure, all
> > other variables held constant, indicating that inversion is a
> > function of exposure rather than pigment load, then I'll eat my
> > words, or a few thousand of them anyway, but I can't eat my
> > pictures. If anyone's interested in a full treatment of my
> > position on pigment stain, I just uploaded that revised page last
> > night. There isn't anything particularly new there; I've said and
> > showed all this here before, I think. One of my goals on revising
> > the site was to cut down on the text, as no one seems to read it
> > anyway, but I don't seem to have accomplished that.
> >
> > http://www.pacifier.com/~kthayer/html/stain.html
> > Katharine
> >
> >
> >
> >
Received on Thu Jan 26 14:24:59 2006