Re: Foxlee Gum Process

From: Katharine Thayer ^lt;>
Date: 06/26/04-02:32:51 AM Z
Message-id: <>

I spent six hours driving yesterday, and thought about this way more
than the topic warrants (I think Chris introduced this only as a novelty
after all) but I didn't have anything else to do while I was driving, so
I kept turning it over in my mind.

One thing I puzzled about a lot was Dave's apparent resistance to the
idea that pressure might account for Marion's observation. He said the
other day that he wanted to understand my thought process. My thought
process is very simple: (1) I'm thinking about this general assertion
(made by both Foxlee and Marion) that if you put unexposed,
undichromated, colloid next to exposed dichromated colloid, and weigh it
down good, that there is a reaction between the unreacted dichromate in
the exposed colloid and the unexposed colloid, rendering the unexposed
colloid insoluble. Foxlee implies that this reaction occurs only in
image areas. (2) This assertion simply makes no sense. (3) Therefore,
there must be some other explanation for the reported results. (4)
Galinsky suggests an alternative explanation: perhaps the pressure
forces the soluble colloid in with the insoluble colloid. (5) I think
this hypothesis makes sense. After all, in both descriptions, the thing
has to be weighted down to make it work, so why wouldn't one suspect
that it's something mechanical that's doing it, since it's almost
certainly not a chemical reaction for reasons that have already been

Galinsky doesn't claim that she has proved that it's pressure, and I
don't claim that for her, although perhaps a careless wording when
writing in haste may have suggested that I was claiming that. No, I was
only interested in the question that was raised, not in whether she made
an adequate test of the question. I agree with Dave that she may not
have tested the question adequately, but whether she did or not seems
rather beside the point of what I was trying to say, which is that when
we are considering explanations for the observations, pressure seems to
me a better potential explanation for the effect than the explanation
that was given, that it is caused by a chemical reaction between the
unexposed and exposed colloid.

In the meantime, I have undertaken a quickie test: first I made a
dichromate-sizing image. I could see the image at first, but by the time
it was developed and dried it had become invisible, which would be
expected after all for one who can't get dichromate stain, as any
visibility of this image would have to be a result of dichromate stain.
When I went to take the print off the line, I thought, well, this isn't
going to work, there's no image there. But when I turned it at a slant
to the light, there it was, a perfect image in white on white,
insoluble sizing against soluble sizing. I can see using this in
something, it's actually rather cool.

Anyway I put pigmented gum on that and dried it, and then cut it in two
pieces and put one half under what serves as industrial-strength
pressure in my shop: the Oxford English Dictionary; that's what I use
when I want to flatten the heck out of something. The other half is in
the dark but not under pressure. This afternoon I will take them out and
develop them for an hour. I really don't expect to see anything, but I'm
willing to be surprised. With this I am testing neither Foxless's or
Marion's methods but two general assertions: (1) that unexposed
undichromated colloid can be rendered insoluble by being brought in
contact with exposed dichromated colloid in the dark and (2) whether
soluble pigmented colloid can be forced by pressure to stick to
insoluble colloid to create an image that is made by mechanical not
chemical means, as suggested by Galinsky.

If a pigmented image forms in both conditions (a most unlikely outcome
IMO) then Foxlee is right, and I will eat crow. If there is a dark
reaction in both conditions, then that would provide support for the
general assertion in (1) but not for Foxlee's claim. If there is no
pigmented image in the print without pressure but a pigmented image in
the print with pressure, that would provide support for (2) and no
support for (1). As I say, what I think most likely is that the
pigmented gum will simply wash off in both conditions (the fact that
Foxlee adds other things besides the gum to make the stuff stickier
suggests that it may not work with just gum and pigment alone) but we'll
see. As I said, I'm not testing Foxlee's method, but simply the general
assertion stated above in (1) and Galinksy's suggestion that Marion's
result could be due to pressure alone causing insoluble and soluble
colloid to intermingle. Marion didn't add anything to the colloid as far
as I know, but h/she was using gelatin rather than gum, so of course
it's not an exact test, but as close as I can get in a quick and dirty
test of the two questions.
Katharine Thayer
Received on Sat Jun 26 09:29:51 2004

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