Re: tonal inversion and pigment loads

On Jan 27, 2006, at 7:44 PM, Yves Gauvreau wrote:

> Katharine,
>
> I should have explained myself more clearly on this. If you look at
> Tom
> image again, you'll see that as the exposure increases, the number
> of "paper
> white" step(s) gets lower and lower suggesting that the lowest
> exposure
> (time) must not be allowed to invert at all, otherwise you get what is
> called "inversion" stains (for now). I think we can all agree on that.

Actually I can't, because I'm not sure what you are saying. Are you
saying that the answer is that you should expose so long that you
push the print tones all the way up to 21 so that there's no room for
stain, making all the steps from 1 to 17 black? And then just develop
for the next month to get rid of the tone back down to the four
actual tonal steps? This doesn't seem to me a reasonable thing to
do. And maybe that's not what you're saying.

To me the place in the middle where there's less tone, is just the
end of the normal tonal scale, the lightest highlights, and then the
stain starts. The hardened gum in the lightest steps forms a bit of
a resist to the stain, less with each ascending step, and so the
stain gets darker with each increasing step. That's all it is.

>
> I'm not sure there is away to get ride of the "inversion" stain
> otherwise
> Tom would have taken them out and this wouldn't even be a problem
> otherwise.

Well, you can't take it out of the thing you've just made, but you
can sure fix it for the next time, by making sure that you remedy the
thing that is causing the stain; either the paper needs more sizing
or the pigment load needs to be adjusted. I keep taking this page
down but someone keeps wanting it back up, so here it is again, the
PV 19 inversion I showed a couple of weeks ago. By reducing the
pigment load by 1/3 and reprinting, I made a nice magenta layer of a
tricolor, shown directly above the inversion, although still just a
touch too pigmented. In other words, it's not that hard to fix an
inversion, just fix the problem that's causing the stain.

http://www.pacifier.com/~kthayer/html/tricolorfun.html

And there's another example on my pigment stain page, in the tonal
inversion part: I show some tonal inversions with burnt umber, and
then there's a link to a similar image of the same subject, printed
with less burnt umber, which prints a perfect tonal scale with no
stain, to show the remedy for the inversion. If you don't want to
read the information, just scan the second paragraph under the
inverted images for the blue link "here." to see the comparison image.

http://www.pacifier.com/~kthayer/html/stain.html

The point being that fixing inversions is a snap, just fix the stain
and the inversion goes away.

>
> The step tablet should be opaque to light for steps and nothing
> should print
> above the first "paper white" step.

Yes.

> The observation we all made is that Tom
> test shows a relatively uniform tone above these "paper white" steps
> whatever the exposure (in these cases).

And that tone, is stain.
Katharine
Received on Fri Jan 27 23:20:56 2006