Re: Drying Handmade Paper

From: Ritab19106@aol.com
Subject: Drying Handmade Paper
Date: Mon, 27 Dec 2004 20:06:32 -0500 (EST)

> I have been applying liquid emulsion to handmade abaca paper, and
> then exposing and processing normally in the darkroom. After
> washing, I have been drying the paper (face-up) on fiberglass
> screens. The paper curls to such an extent that, even when placed
> for days in a (cold) dry mount press, it emerges looking very
> wrinkled.

How brittle is your print emulsion when dried like that? If it's very
brittle, your emulsion lacks gelatin plasticizer and this is the No. 1
suspect.

Ideally, prints should be dried in rather cool to cold room with RH 30
to 60%. Practically, avoid warm dry environment for drying. Gelatin is
very brittle in dry warm air.

You can soak the print in 0.5% triethylene glycol solution before
drying to see if it helps a bit. Another thing you can do is to use
rather strong solution of PhotoFlo 200. But the effect of these
treatment is rather limited. (These are gelatin plasticizers but they
have to be applied as the last step in the processing because they are
diffusible or washable.) Since these solutions have some weak
humectant effect, you shouldn't use them too strong. Old
recommendation for glycerol also works but I don't recommend it
because of its strong humectant effect. Final glycerol treatment
should be considered non-archival.

You might want to try blending Rohm and Haas Rhoplex AC-33 into
emulsion. You can buy 250ml of this product as Primal AC-33 from
Kremer Pigmente. Primal is the name Rohm and Haas uses outside the
U.S. for this product. In each 100ml of emulsion, you might want to
blend 5 to 10 ml of this product with good agitation. Exact amount
varies with emulsion, but I usually use 1 to 3 ml of this product per
gram gelatin in the emulsion.

This additive makes gelatin layer more durable during wet processing,
but it also makes gelatin more plastic than plain gelatin. The effect
is much better than immersion in triethylene glycol. With 300g/sqm
watercolor paper, my prints dry flat with some weight. (I use AC-35
for sizing blend, AC-33 for emulsion blend.)

Another possibility is to coat 5-10% gelatin solution on the back of
the fully processed print when it is half dried. I don't know about
today's films but this is one trick used by photographic industry to
reduce curling as well as providing retouchable surface. I don't
recommend you to do this on papers unless the print is fully processed
and washed, because washing print is much more difficult once gelatin
is applied.

There are other gelatin plasticizers like sorbitol, dextran and other
sugars. Commercial emulsions also blend in other stuff like latex
polymers, colloidal silica, etc. in addition to gelatin, but I don't
know if the liquid emulsion products use the same technology as what
they use for their own films and papers. (I doubt it.)

--
Ryuji Suzuki
"People seldom do what they believe in.  They do what is convenient,
then repent." (Bob Dylan, Brownsville Girl, 1986)