Re: Foxlee Gum Process

I probably should not say too much, but if I only read from the information
below, I think in the case mentioned, Gallinsky probably just misunderstood
Marion's writing, and she subsequently did a wrong test and so she couldn't
duplicate Marion's observation (though from Marion's writing sounds like
s/he probably didn't quite understand what was really happening either).

What Marion did was to exposed the dicrhomated gelatin *UNDER A NEGATIVE*,
so the exposed parts get hardened, but there are unexposed parts with
unhardened gelatin and dichromate left. When another piece of undichromated
gelatin is placed in closed contact with the exposed gelatin, the leftover
dichromate hardened the undichromated gelatin. The amount of leftover
dichromate is proportional to the exposure, which is inverse proportional to
density of the negative, so Marion got an image. I think humidity would help
here, but we don't know the condition of Marion's lab.

In Gallinsky test, she exposed dichromated gelatin until maximum
insolubility! The is no leftover dicrhomate, no unhardened gelatin which to
retain some moisture. No wonder she didn't get any image. But then her
conclusion is about squeezee! That is an example of how we sometimes make
"logical" conclusion but might not be right because not all the parameters
or information is known.

Dave S

----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Thursday, June 24, 2004 6:30 AM
Subject: Re: Foxlee Gum Process

> Chris,
> This is quite similar to Marion's 1873 (Phot News 17:242) observation.
> described by Galinsky in 1930 (Biochemical Journal 24: 1706-1715) that
> "if a dichromated gelatin film which had become insoluble by exposure to
> light under a negative were placed in contact with a similar but
> unexposed film and the two were squeezed together under pressure, the
> gelatin in contact with the exposed gelatin became insoluble after 8-10
> hours and a print of the image was obtained. It was concluded that once
> action was set up by light in a dichromated gelatin film, this could
> induce the same change in gelatin placed in contact with it, without
> exposure to light.... The present writer attempted to reproduce this
> change in the absence of any mechanical influence, and found that no
> such alteration occurred."
>
> She exposed dichromated gelatin until maximum insolubility had been
> produced, and then added a gelatin coating and left the whole in the
> dark for 24 hours, then for two weeks, and then four weeks, and found
> by analysis that there was no change in the added gelatin regardless of
> the length of time it stayed in contact with the exposed gelatin. She
> concluded that a more probable explanation for Marion's observation was
> that the squeezing caused the insoluble material to impregnate the
> soluble gelatin in contact with it, thus making it more difficult to
> dissolve, although there was no actual change in the added gelatin
> itself.
>
> Katharine
>
> Christina Z. Anderson wrote:
> >
> > This list has been so darn quiet this week I figured I might as well
post
> > another historical gum blurb!
> >
> > This is the oddest process, so just a point of interest that maybe
> > relates to nothing, or maybe something. It is the "indirect pigment
image".
> > Sized paper, gelatin.
> > paper sensitized with a 2.5% pot bi.
> > Paper exposed.
> > Paper developed so nothing remains except a faint positive.
> > Paper is dried, and can be pigmented right away as per below, or saved
for
> > weeks later.
> > To pigment: 5 parts 40% gum to 1 part glycerin to 2 parts acetic acid
to
> > 8-10 grains dry pigment.
> > Coat and dry the paper, leave under pressure for 30-36 hr, like under
books,
> > and then cold water develop, no exposure. It'll automatically develop in
an
> > hour.
> > Based on, get this, Foxlee's idea that the action of light set up in one
> > colloid is transferred to, and continued in, another which is not
exposed to
> > light at all. (mind you, no bichromate has been supposedly washed out
in
> > the water). Foxlee prefers to use starch as the sizing colloid, but
Griffin
> > prefers gelatin.
> > Advantages: no rush to develop. Pigmented coat not printed thru so it
> > doesn't need to be carefully applied. Hardening from bottom up, so it
is
> > more durable.
> > Weird
> > Chris
>
Received on Thu Jun 24 12:24:57 2004