Re: yellow gelatin

Judy says:
> The good news is that, as I've mentioned, the yellowing can be avoided,
> but the bad news is that it usually takes a while (at least IME) to show
> up. Except for direct effects of an alkali you don't see it right away.

So you're saying the yellowing can be avoided by your two methods of only
using 15cc of the glyoxal, and rinsing the paper after the glyoxal
application.. and that the yellowing altho not showing up immediately will
show up later. In what way? When? If I remember, the yellowing described
in detail on this list was mostly on paper not used right away, correct?
That it happened pretty rapidly, due to unknown sources, either exposure to
oxygen or light or non exposure to oxygen or light, as seemed to be the
usual non-consensus of the list.

My glyoxal is already very yellow, and *even so* the coat does not look
yellow on the paper.
If it happens slowly over time AND gets worse and worse to the point that it
degrades an image, this is a problem, but one we will only know years from
now. Maybe we'll be in the history books as an archival nightmare. The
worry is not enough to make me want to start using formaldehyde.
>
> They were putting an overall tone on the paper itself which you don't get
> in a gum print unless you've been VERY bad... the "buildup of dichromates"
> at least as I've seen it (though with sweet NYC water it's rare) is
> usually brown and only in the *image.*

Yes, I realize this...my point was--perhaps not clearly made-- that the
shift in tone of the pigment, as you mention the pigment color change, is
all the yellowing I would ever think to need, so when I came across the
historical mentions of "warming up" an image I was really surprised. I even
tried it on one image, and it does look kind of cool, like an old
photograph, but not my cup of tea. Its existence in the highlights takes the
zing away from the image (I made a wall at school of reject gums, and this
is on it).

When I clear a print, there is a definite cooling of the image. Anywhere
there is gelatin hardened and left behind, there is a modicum of residual
dichromate, which is yellow. Sometimes it is slight enough to only be
noticed when clearing a print and clearing only half the print to see the
color change, as in, if you were making a class example of it. Very
interesting. Actually, I do it on my Stouffers wedges quite a lot to see
how much the steps are affected by residual dichromate.

<snip, here> I doubt ALL can be cleared out -- if so, what's the color
change from?
>
> Judy

Good, this is what I need to know (the Sil thing).

I'm thinking that dichromate does not get yellower with age...but if glyoxal
continues to yellow through years, that is a concern. Kind of like using
varnish on the prints. Speaking of which, the varnish recommended was mastic
mixed with methylated alcohol (1:7), which one book said was the common
artist fixatif, so, Judy, try that.

I did leave as I said my glyoxal gelatin outside in the sun for a week,
along with leftover glyaraldehyde gelatin, and the glut was white, the gly
was yellow, but neither changed color to a darker shade nor did either
harden the gelatin even more than a very stiff like Jello-blox kind of
thing.

I will be side by side testing glut and gly this weekend.
Chris
Received on Wed Mar 24 06:06:23 2004