Re: gum "stain" with zero exposure... etc.
Judy, far from me to claim that I understand what happens. I was commenting on your citing of Mike Ware: "The less viscous the emulsion...the more it soaks into the paper, hence the more stain". In the case of glass, where this tonal inversion or "stain" happens also, there's no "soaking into the paper" for any viscosity you might have, so the "stain" must have some other origin. According to what I have noticed, the pigment causing the "stain" just sits there on the paper or glass surface, apparently free of any gum. It is also very easy to remove manually (i.e. with a thin brush), since it doesn't seem to be bound to the surface in any obvious way.
So what seems to happen is that the gum in these regions, as expected, is washed away but for some reason a little of the pigment stays put. Could be some form of electrostatic binding, I don't really know.
BTW I call it "stain" because I don't think that it is stain in the usual sense, i.e. pigment getting stuck between the paper fibers that will not clear.
On Wed, Oct 7, 2009 at 8:22 PM, Judy Seigel <email@example.com> wrote: