Re: Image formation in gum

On Dec 16, 2005, at 8:32 AM, Katharine Thayer wrote:
>
> I have prepared a page that shows that same effect in a different way,
> but I just realized that I don't know how to do something in my new
> version of GoLive, and I can't upload the page til I figure that out.
> So it will be a bit longer. On my page, I show the tonal inversion in
> images which are underexposed, so that it's abundantly clear that the
> gum layer wasn't hardened completely.

Okay, here it is

http://www.pacifier.com/~kthayer/html/inversion.html

I wish I could claim credit for thinking of underexposing the images,
but it happened because we were in one of those rare times, once or
twice a year when the wind comes from the east instead of off the
ocean, and even though I doubled and tripled the usual exposure time
for this paper negative to adjust for the lower humidity, it wasn't
enough additional exposure. But it shows the effect better, I think,
when it's clear that the gum layer isn't adequately hardened,
especially in the one where I just let the incompletely hardened gum
dissolve completely off the paper.

And to stress the point, what I think interesting about this is what it
might say about top-down hardening; even though it's obvious that the
gum wasn't hardened through, I don't know how to account for the
negative image except by supposing that the colloid at the paper level
must have been hardened enough to form a resist that kept the excess
pigment from depositing on the image areas.

Katharine
Received on Fri Dec 16 12:39:07 2005