Re: tonal inversion and pigment loads

> 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

Where there's no exposure (no gum) there's
> maximum stain. Where there's a little gum, the stain is a little
> lighter than where there's no gum. Where there's a little more gum,
> there's a little less stain. Where there's maximum gum, there's no
> stain. Hence: steps; hence: inversion. As I said before, of course
> exposure is necessary to create an inversion, because exposure is
> necessary to create an image. What's cool about the inversion is
> that it's a tonal (though reversed) image, but the image itself isn't
> made of hardened gum; the hardened gum only acts as a resist. The
> visible image is made entirely of pigment, deposited as stain. It's
> very much like a gumoil print, where the gum is a resist and the
> positive image is made of oil paint, except that rather than applying
> paint in a separate step, the pigment stain is deposited in the same
> printing that gives you the gum resist. For gumoil you would use a
> positive rather than a negative to create the gum resist; since in
> this case you're using a negative to create the gum resist, you end
> up with a negative image instead of a positive. But if you wanted to
> play with this effect (if you could figure a way to reproduce it
> reliably, as I can't seem to) you might want to use a positive
> rather than a negative.
>
>
>>
>> As far as pigment load, I thought I would share my method that has
>> taken me through 1000 (no s--t) prints: I mix 1 tube of 14/15ml
>> watercolor paint (not pigment powder) into 45 ml gum--this makes
>> 60ml solution. At time of use, I use this stock solution in this
>> ratio:
>>
>> 1 tsp stock pigmented gum:1 tsp plain gum:1 tsp water: 1 tsp
>> saturated am di.
>
> It's interesting all the different ways to get to the same place.
> Instead of mixing the same stock solution for all pigments, I mix
> different stock solutions for every pigment. I don't measure, I just
> dump in paint til the color looks "right" for that particular pigment
> (usually at maximum color saturation, but less saturated for tricolor
> reds and blues for example) and then I use that mix 1:1 with
> saturated ammonium dichromate. I don't add more gum, unless for one
> reason or another I want to print the color paler than the stock
> solution, and I never add water.
>
> Chris's basic mix looks to be about 6% paint, which is what I figured
> both of our pthalo mixes to be when we had that earlier conversation
> about pigment loads. But it sounds from this like she mixes strong
> pigments (which I would consider pthalo to be) at less than that, in
> which case I may be using more pthalo, which makes my caution about
> not paying attention to labels ("a lot," "not very much") even more
> appropriate. And I use considerably more of other pigments than I do
> of pthalo. I've put a whole tube of pigment into 20 ml of gum, but
> that was when I was trying to make a light and weak pigment (Bohemian
> Green Earth in that case) stronger and darker by using more of it,
> which is kind of like trying to make up for a unit loss on items by
> selling more of them.
>
> The point about pigment loads is that gum can easily handle any
> pigment at full color saturation, with no problem. Once full color
> saturation is reached, there's no point in adding more pigment. If
> you keep adding pigment beyond color saturation, you will reach the
> point where the gum simply can't hold all of the pigment in
> suspension, and then you run into those weirdnesses we've been
> talking about, like stain and inversion. People who have never run
> into these things, as I said the other day, have been smart enough or
> lucky enough to keep their pigment loads under the limit of gum's
> capacity for holding pigment. I wasn't, in the beginning; I used too
> much pigment and experienced a lot of staining, and that was on sized
> paper. But once I understood that it takes less pigment than I
> thought to achieve full color saturation, then I never had pigment
> staining any more, and could print on unsized paper without a problem.
>
> Tonight's Pineapple Express is roaring in right on schedule, and
> especially ferocious tonight.
>
> Katharine
Received on Fri Jan 13 00:10:44 2006