Re: Glutaraldehyde again

>Katharine said, huge snip by me: I mixed this glutaraldehyde at .04% as a
proportion of the gelatin
> solution; I think I figured out once that Chris mixes hers at .015%, so
> it's possible that I used too much of the glutaraldehyde. But this is
> just another one of many reasons why I'm not convinced that
> glutaraldehyde is the way to go.

Good morning! Verrrrry interesting, Katharine.
     Katharine, you're right; I mixed 6 ml of 2.5% into 1000 ml of 2.8%
gelatin, using on all different kinds of paper. I gave 2 coats on half and
one coat on the other half of about 50 large sheets. I did the same number
of sheets the second time, but the second time I used 3ml only of 2.5% per
1000 ml gelatin.

I spray developed 3 layers of gum on every one of those sheets, and the only
problem that came up was the Rives BFK with the 3ml glut and only one layer
of size, that was undersized on the top little teeny heads of the fibers and
stained with thalo blue speckles in the highlights. My coatings were
absolutely stable--even with full on spray.

I had no unevennes of coating or spottiness or any sizing issue. And I went
through all those sheets within 4 months. Next time I size I'll save a few
sheets and store for a few months and see if this appears suddenly also.
But I do think that the amount of glut was probably the cause of the
problems. Oh, I brush sized, not tray soaked.

The only thing that unnerved me the first time I used glutaraldehyde was
that the coating did not appear to sink into the paper right away, which is
why I went to the lesser amount. However, those 6ml sheets did not present
any problems.

The way I see it, we have alum, glut, gly, and formaldehyde. I'm not
willing to use formaldehyde--if my husband walked into the house and smelled
a chemical, he would finally know how much chemistry I fool around with, and
freak (so far he thinks it's just jello). Alum has been, in a number of
sources, called into question as far as archivalness goes (anyone know
anything about this and if it is true and why it would be true???) and in a
couple sources said to cause graininess (perhaps a scapegoat) and shrinking,
and glyoxal has yellowing problems for some, including me.

If glut was problematic, I would go back to glyoxal fairly happily, though.
Right now I'm using unsized Fabriano Artistico all summer, and it works, but
I much prefer having sized paper. My development times are more predictable
and less. I have to spray and spray.

One more thing: I'm still thinking about your statement that you never have
dichromate staining in any of your step wedges. I did a series of wedges
from pale to deep color, at same exposure times, to see the relationship
between pigment and scale, and the dichromate stain is very perceptible in
the pale ones and not as much in the deeper shades. I cleared half of each
side of the 4x5 step wedge to show the comparison between the cleared and
uncleared colors. In every one, there is some dichromate stain that has
cleared--the color becomes cleaner and less yellow, albeit more perceptible
in the paler shades. This is with the low dilution dichromate, too. Which
leads me to believe that a lot of the differences you and I perceive in gum
may relate to exposure, as I expose heavily enough to allow a good full
spray development, but a half hour development time or less. The unsized
paper takes an hour.
Chris
Received on Sat Jun 12 08:32:41 2004