Re: tonal inversion and pigment loads

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 11:31:52 2006