Re: Foxlee Gum Process

> BUT, with what Dave is saying, if I read it correctly, AND with the
> fact that acids will insolubilize gum without exposure, I think what is
> happening is that with pressure the layer of pigment is adhering to the
> image gum left on the paper as per Dave's suggestion (glycerined pigment
> adhering to the hardened gum layer where water does not soak in, but not
> adhering to where the paper will swell with water, correct Dave?) but the
> hardening that occurs to the layer is probably due to acid, not
transferred
> bichromate (which is why 36 hours was necessary; if it was developed right
> away, the gum might swoosh off).

Hi Chris,

Actually my explanation is that there is no hardening. The acid doesn't
insolubilize the gum. The gum has been insolubilized by exposure. The acid
simply breaks the glycerin so that the ink attached better to the already
insolubilized gum.

And I think the reason to wait for 36 hours is so that the "oily ink" can
dry up at least a little.

> The fact that Foxlee and others practiced his process, as did Marion
> practice his, means that something was going on, but that the "something"
> they thought was going on, wasn't, is very likely.

I think so too.

> I'm really only interested in it because it seems like so much work
> when they could be just doing a gum print the easy way. I think wanting
> acclaim for new inventions was uppermost in their minds.

Well, there is actually some advantage to their process. One thing is since
pigment is not added to the colloid, you don't have to worry about staining.
You probably don't have to worry too much about sizing it either.

But I don't know if they truly "invented" the process. I think that many
processes at that time are similar. Afterall, the main thing is simply to
harden the colloid by exposure, and then process it to get an image (one can
use it positively, negatively, mix in pigment, apply pigment later, etc.
etc.) but the basic mechanism is the same although the working procedure to
get the image varies greatly. I don't mean to imply that they lied or
claimed undued originality, but they themselves might not understand the
process that well at that time either.

Dave S

> ----- Original Message -----
> From: "Katharine Thayer" <kthayer@pacifier.com>
> To: <alt-photo-process-l@skyway.usask.ca>
> Sent: Thursday, June 24, 2004 5:30 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 Jul 15 19:43:23 2004