Re: Foxlee Gum Process

Dave Soemarko wrote:
>

>
> > As I've said, I don't think your explanation works because
> > it predicts that the entire print would become a wall of insoluble
> > colloid, rather than the image being retained.
> >
>
> If you assume that even the insoluble part still has enough dichromate to
> harden the other gelatin sheet, then the whole print would indeed be a wall
> of insoluble colloid; but my argument is that the insoluble is not really
> playing much, if at all, it is the insoluble part that comes to play; that's
> why one would get an image.

Whoa, I missed a turn there, they are coming too fast for my old legs.
So you're saying that the image that was created in the first exposure
becomes the negative for the negative image that's created by the dark
reaction? So you'd need to use a positive to have the image come out
right? Okay.....

But this isn't what I thought Chris was describing.....

> I replied about Foxlee's process separately. I think, again it is just my
> opinion, that Foxlee uses a completely different mechanism. In the Foxlee's
> process, the oily ink sticks to the insoluble gelatin, but the print is then
> immersed in water again, the soluble gelatin absorb water, and water repels
> oil, so this part get cleared. This is more closer to gumoil (except that
> rather then immersing in water, the print is cleared by wiping, but the
> principle is similar, the oil attached stronger to the insoluble part
> because there is no water whereas it is more readily to be wiped off from
> the soluble gum part), or similar to acrylic-gelatin method that one wrote
> in Photo Technique (except that there the principle is the acrylic would
> attach itself to the insoluble part, whereas the soluble gelatin is washed
> by HOT water). In this case (Foxlee), it is another clever use of the same
> concept except that oil-water characteristic is utilised.

I missed the part where you said you think Foxlee and Marion are
different processes; I'm going by the identical explanation they make
for their result, that the result is caused by a reaction that transfers
from the exposed dichromated colloid to the unexposed colloid.

 I don't see anything in Chris's description about oily ink, only a few
grains of dry pigment, and I don't see anything about using a positive
rather than a negative. And while I think the whole lithography
explanation is interesting, I'm not sure I buy that the reason this
works is that it's actually lithography not gum printing after all. But
it does satisfy the criterion for an explanation that makes sense and
explains why there's an image and only an image, because it doesn't have
anything to do with dichromated colloids. But it doesn't explain Marion,
so then where do we go.

> And I am thinking that it works similar to dye transfer, since the first
> gelatin sheet is hardened proportional (from the top), the dichromate will
> get into the 2nd gelatin sheet in proportional thickness as well.

 I can't find my book that describes the dye transfer process, so I
don't know how apt a model that is for what we're talking about here,
but surely even if it is, the proportionality would be inverse, which
takes us back to where we were.

This is getting impossibly confusing. I'm beginning to think we're
talking about completely different things so it's no wonder we're
talking past each other. I think this is my stop; I'm off this bus.
Katharine
Received on Thu Jun 24 16:03:19 2004