Re: Eastern European RC papers

----- Original Message -----
From: "Ryuji Suzuki" <rs@silvergrain.org>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Monday, January 23, 2006 11:23 AM
Subject: Re: Eastern European RC papers

Although your suggestions are good ones, I think the real
problem is
somewhat blurred. Lack of gelatin overcoat and insufficient
gelatin
hardening may be seen as a problem by some users (such as
students who
don't handle RC prints carefully) but I don't think they are
closely
related to archival property given proper handling.

For example, I've been making enlarging and contact printing
emulsion
with no protective layer for some years but with careful
handling I
have not seen a problem.

This kind of image deterioration involves redox reactions.
RC paper
has a generator for a strong oxidizing agent in the
polyethylene
layer, for which companies in the west spent considerable
effort (and
many mistakes) in 1970s, 80s and early 90s. Manufacturers
like Ilford
and Kodak told users that the image deterioration was caused
by poor
processing and washing, and the problem does not lie in
their
products, while they secretly improved the formulation of
the resin
coat. And every time Kodak said there was no more problem
with their
RC papers, a new problem was found.

But putting too much focus on the RC is also very misleading
in my
view, because simply using baryta paper does not ensure good
permanence. The most effective way to prevent such
deterioration,
regardless of RC or FB, is to (1) treat the print in a
sulfide toner,
AND (2) store prints in a dry place. Residual thiosulfate is
often
blamed, but if the RH is kept low during storage, a small
amount
(still several times higher than ANSI limits) of residual
thiosulfate
is harmless.

  If I understand this right you are saying that there were
problems caused by the resin itself, independent of the
trouble caused by the Titanium dioxide reflective coating.
Is this correct and can you either expand on it or give a
reference that describes the effect more fully.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com