Re: Image formation in gum (2)

On Wed, 21 Dec 2005, Tom Sobota wrote:
> ....The actual times are not important, of course, but this image
> shows that perhaps 'pigment stain' and 'tonal inversion' are two different
> effects. Both are probably related to pigment concentration,

I've ruffled feathers before with this, but, as Dooley said, facts is
facts. The relation of pigment stain to pigment concentration is only
proportional -- that is, if you're getting pigment stain with a little
pigment, you could expect propartionately more stain with more pigment,
but there is not (as per our old friend Paul Anderson) a magic line above
which stain starts to happen, and below which it doesn't.

In fact, as shown on page 46 of Post-Factory #2, more pigment can actually
produce less pigment stain. I surmise that that's because more pigment
makes the emulsion more viscous, or thicker, so less likely to soak into
the fiber of the paper... The *curve* then becomes much steeper, that is,
with fewer steps, as pigment density blocks up the bottom steps -- but,
again, pigment STAIN may well be less.

J.
Received on Wed Dec 21 19:55:19 2005