Re: Hardening gelatin

Judy Seigel wrote:
>
>
> Extrapolating from one use of gelatin, or gum, or dichromate to a
> different use is IME almost bound to be wrong -- as for instance
> extrapolations made about gum bichromate from Kosar's citations about
> carbon. Even if the chemistry is the same, or similar, the mechanics are
> quite different.

Yes, we're in complete agreement on this, I think. My whole purpose in
that paragraph was to make that particular point.
>
> The only test for adequate hardening that I find relevant would be if
> there's pigment stain or not -- because that's the reason for hardening
> our gelatin (whatever it may be in Ryuji's use) in the first place.

The question of a laboratory test for telling when gelatin is hardened
came up when I wanted to compare the hardening of gum to the hardening
of gelatin, to settle my mind about something from an offlist
discussion. When I realized that there's no way to compare the two in a
way that would make the results interpretable, and when it became clear
that my correspondent and I were actually in agreement on a point that I
thought we differed on, I lost interested in this comparison. But the
question still puzzles me purely from a standpoint of intellectual
curiosity.

But since I don't get pigment stain either with UNhardened gelatin or
with no gelatin at all, I can't quite see how pigment stain would be a
useful test for whether gelatin is hardened or not.

I guess I always thought that the conventional reason for the gelatin
was to avoid pigment stain, and that the reason for the hardening was to
make the gelatin less susceptible to moisture and insects. So I've just
learned something new; that the hardening is considered necessary to
avoid pigment stain. Since I don't ever have a problem with pigment
stain, this is something I've not had to think about I guess.

When I started gum printing, I sized because that's what all the
instructions said you were supposed to do, although I couldn't see the
point in hardening, as I've already explained. But one day I got a call
from a gallery saying that they'd sold four tricolor prints and would
like another four as soon as I could get them there. I didn't have an
inventory of prints, and I didn't have any sized paper on hand, so on an
impulse I grabbed four pieces of paper right out of the box and printed
four tricolors, one of which is on the opening page of my website.

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

When I saw that I got no pigment stain on a three or four layer print
with no additional size, I never sized again. That is, I never sized
again until I used Fabriano Uno for a few months in 2002. The reason I
had to size that paper had nothing to do with pigment stain; it was
necessary because without added size the paper printed with attenuated
DMax. (It was interesting to me when Sandy made the same complaint about
this paper using a different process.) Some might wonder why it mattered
to me, since I was printing deliberately high key images at the time
anyway, but the thing is, I wanted the DMax I expected even if it was a
very light DMax (I printed with very very small amounts of pigment to
get the light tones I wanted); I didn't want the paper taking away
anything from what I expected the gum to do. But in order to get the
DMax I expected, I had to size the paper. I really disliked that paper,
and now I'm printing on unsized Lana aquarelle.
  

> a printer who makes gorgeous gum prints without hardening her gelatin
> size, and

As I've said, I neither size nor harden; whether my prints are gorgeous
or not I leave to the judgment of those who buy them.

Katharine's point that the dichromate probably tans or hardens
> the gelatin may apply -- although I'd guess that it only hardens where
> there's been hardening by exposure, so the paper whites -- which is where
> stain happens, or anyway where it's an issue -- wouldn't be hardened that
> way.

That's what I meant when I said that the hardening would only work if
there were tone throughout the image. It wouldn't work, for example,
with an image like this,

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

because wherever there is white the size wouldn't be hardened any more
than the gum is hardened in those places. But I didn't size that paper,
so it's not an issue, and obviously pigment stain isn't an issue either,
or the whites wouldn't be white. As I said above, it hadn't ever
occurred to me before that hardening is considered necessary to maintain
paper whites; I just thought it was to make the gelatin more archival.

>
> > I've never hardened gelatin myself in practice; even back in the
> > beginning when I routinely gel-sized my paper, I didn't harden the
> > gelatin for two reasons:
> > (1) I figured that if the paper manufacturers don't harden their gelatin
> > sizing, why should I? That's a somewhat flippant comment, because the
>
> I'm wondering if that's true -- don't most papers have alum?

The only one I was interested in at the time I was pondering this
question was Arches, which I used for more than a decade and which used
gelatin as a factory size, at least that's what they told me when I
asked, that they used gelatin and they didn't harden it, but they did
add a fungicide. I can't speak to other papers, except that Fabriano Uno
uses some nonspecified size that's not gelatin, and I hate it.
 
>
> Well again, I think the paper whites are the issue,
and have the
> impression (wrong perhaps) that the tanning action of dichromate depends
> on the exposure to light, not just applying the solution.
In the white,
> or very light areas, exactly where it's needed, that hardening wouldn't
> occur.

No argument here, except for the part about hardening being necessary to
maintain paper white, which for whatever reason I don't seem to have a
problem with. Peace,
Katharine
Received on Tue Mar 30 18:43:45 2004