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 11:26:58 2004