From: Christina Z. Anderson (zphoto@montana.net)
Date: 08/17/03-09:34:18 AM Z
<Judy said> Actually, I think there was something in the 1905 Gum Bichromate
book
> along those lines by someone else, so Mr Wille wouldn't have been the
> first... but my point isn't who thought it up.
Yes, there is, but not the same titration test. It is the bend test.
> You note that Maskell and Demachy addressed pigment stain. I note that
> that was 2 paragraphs of a 38-page treatise, or more or less in passing...
> THAT was the "importance" (or lack thereof) in the other early works as
> well.
Yes, and as I also quoted at length in a previous post of a month or so ago,
Demachy himself didn't have a problem with pigment stain and wondered what
all the fuss was about.
>
> I surmise that it became so important with Anderson because he was
> printing with 100% saturated sodium dichromate which he used about 2 parts
> to one part gum--- as would make a stone give off pigment stain, and is, I
> guesstimate, about 100 times the dichromate other printers used.
As I also stated in a post a couple weeks ago, 100% sodium
dichromate--100%!!--is not that fast. I found it to be less fast than
ammonium dichromate, which blew me away. I will certainly retest this and
see if I am mistaken, but the assumption that 100% sodium dichromate would
be, let's say, 3x as fast as 30% ammonium dichromate does not seem to be
true with my limited testing. I will certainly redo this test, because I
have a liter of the stuff sitting around and I don't plan on using it in my
practice except to do silly tests :) but it really surprised me. The only
thing I could think of was that the thickness of the syrup held back light
more than one thought, or maybe just maybe my am di that day was SOOOO hot
(doubtful) that more went into solution. So, to be fair, I'd really have to
make sure my room temp is around 70 and retest. To me, the primary reason
for not using sodium dichromate is that if you use a saturated solution
you're using way too much dichromate for the same result--no more "bang for
your buck".
> As for how it got into the canon -- I've said this before: It was the
> ZEITGEIST !!! In 1939 (year of Henney & Dudley) Kodak was gaining
> ascendancy with its factory materials. Kodak types were coming up with
> all these tables and charts and curves and of course when you sell factory
> film & paper you *have* to provide the tables & charts & curves showing
> how to use them.
<etc., big snip>
This I find FASCINATING.
> Otherwise they would have had Franklin Jordan, actually better known at
> the time & who knew more about gum printing, do the chapter...
I find this assertion interesting: Jordan's book is written very
cavalierly: a bit on the "flippant" side. I wonder if they didn't
appreciate his jocular attitude?
> > I. Degraded Highlights
> > A. Insolubilization of the gum/pigment on the paper
> > 1. Insolubilization due to light exposure
> > a. Fogging or accidental non-image exposure
> > b. Overexposure
>
> Did you test these assumptions ? For instance, I dried coated prints for
> 1/2 hour IN ROOM LIGHT, and found NO extra pigment stain... though more
> dichromate stain. Although a too thin negative may well "fog."
I've been using room light and have no fogging. It'd have to be accidental
exposure stronger than roomlight. But technically, how can we know whether
it is fogging or just too much exposure?
>
> As for simple overexposure with a reasonable negative, longer development
> will clear it. And in the normal course of printing, unless you've heat
> dried or gone to lunch & left the light on, or left a coated paper at room
> temp to "age,"there rarely is such a thing as "insolubilization."
> Judy
>
I've had enough prints where longer development did not clear. In fact,
there were some I left for 24 hours in the water, hoping.... So
insolubilization is definitely a factor. Well, obviously it is because that
is what we are trying to do with gum printing when you think about
it--insolubilize the gum enough so that pigment stays where we want it, but
not too much so that it stays in the highlights. And this can happen with
or without exposure, as delineated in the outline.
Chris
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