Dick I think it's possible that platinum/palladium and kallitype coat
differently. My sense of the situation, my *recollection* (I haven't done
either for several years) is that the pl/pd makes a syrupy concoction, the
kallitype more liquid like VDB. It, I believe, will soak into the paper
more, and can, therefore, get greater D-max by coating heavy.
I've noticed in cyanotype, BTW (haven't made these tests in other media),
that, as I have mentioned, with some papers double coating increases
D-max, with others it decreases, wiping off emulsion.
> Ziatype and the Ware platinum processes are especially prone to this
> problem due to the printing out function which is self masking. The masking
> by its nature makes the coating thin and any wash-off of surface black only
> reveals the white paper underneath.
Sorry, I don't get that -- you mean that a shadow area can become
completely white from self-masking? I've never seen that.
> ....I've examined
> prints under a microscope and often see grain that is like white lines. My
> theory of what is happening is this. During coating the brush scrapes the
> surface of the paper and raises up paper fibers. Raised fibers may also
> occur naturally in some papers. Visualize some fibers is sticking up like
> miniature telephone poles, and assume some degree of transparency. The
> result is light during exposure strikes the emulsion on these fibers from
> all directions, including from the opposite side of the fibers. The
> consequence is that the emulsion on these fibers gets far more exposure
> than those fibers laying flat. The result is that they then solarize and in
> effect, revert back to white. This will happen mostly in the dark areas of
> the print.
I've never seen solarizing in platinum, but I have seen it in cyanotype,
where it doesn't at all become paper white, but a lighter blue. Are you
sure that paper white you notice is solarizing? Have you seen solarizing
to paper white in other parts of the print? As noted, I never have, tho
it sounds great.
However, I do have test prints in cyanotype on Rives BFK which show white
lines something like you describe. I haven't looked at them under a
magnifying glass, much less microscope. But since, as noted I've never
seen solarizing to white with cyanotype, I've always assumed it was caused
by fibres sitting on the surface, then washing off, leaving the area under
them either uncoated or unexposed. Well, it really doesn't *look* much
like that, but I couldn't think of any other explanation.
I left my microscope at the laboratory, but will take a look by
magnifier..
cheers,
Judy