Re: Stain and exposure (was: Re: Gum image has reversed

On Jan 10, 2006, at 10:19 PM, Katharine Thayer wrote:

>
>
> For the most pigmented mix, while there were fluctuations in the
> lightness and darkness of the stain, probably as a function of how
> much of the gum emulsion had flaked off (which didn't seem to be
> directly related to exposure)

It might be worth pointing out that for prints 1 and 2 (there, I
found a use for the numbers I put on them) the gum emulsion flaked
off entirely, and what's left on the paper is pure indelible stain.
On print 4 the gum emulsion is almost entirely gone; all that's left
is her hair, the border, and some small dark areas within the fan;
the rest of the "tone" on the paper is all stain. Why the gum
emulsion didn't flake off of print 3 is another of those mysteries,
but the whole question of why some of these flaked and some didn't,
in a sort of random-appearing way that doesn't seem to be directly
related to exposure, I suspect has to do with subtle differences in
how the coating went on, perhaps even minute differences in how damp
the brush was.

The coatings appeared completely smooth and even as they brushed on.
But the "smoothing" step following the coating had little effect on
these overpigmented coatings, as I showed with the coating on the
newspaper. It was like trying to brush out printing ink or something.
It just sits there, it doesn't spread out and settle into a smooth
even thin layer as a normally-pigmented gum coating does in the
smoothing step. So any brushstrokes or coating unevenness in the
initial brushing on of the coating just stayed right there in the
coating. (You can see these unevennesses and brush strokes especially
revealed in the stain of the top row where there's no gum emulsion
left). This uncertainty and variation in the smoothness or
thickness within and between these thick coatings is what I think is
responsible for there being no clear relationship in these test
prints between exposure and whether the hardened coating flaked off
or not. Most of these did; my sinks were full of bits of black
hardened gum. I really hate working with overpigmented lamp black;
it was a mess cleaning out the brushes, the sinks, everything was
black and gucky.

I said initially that I don't think there's much to be learned here,
but on reflection I think what's to be learned is that if you put too
much pigment in the gum, weird and unpredictable and often unpleasant
things happen, but there's no need to overload the gum with pigment,
and if you don't, you'll get much better results. That's all folks,
Katharine
Received on Wed Jan 11 15:58:11 2006