U of S | Mailing List Archive | alt-photo-process-l | Re: Eliminating CaCO3 in buffer in "archival" watercolor papers

Re: Eliminating CaCO3 in buffer in "archival" watercolor papers

From: BOB KISS <bobkiss@caribsurf.com>
Subject: RE: Eliminating CaCO3 in buffer in "archival" watercolor papers
Date: Sat, 16 Aug 2008 10:39:52 -0400

> A late question: What concentration of Na4 EDTA do you
> recommend to remove the CaCO3?

This should be determined experimentally, but I'd start with
1%. If you want to do this right, this is how I would do:

1. Establish a measurement method for calcium in paper.

2. Run parallel treatments; one piece in water, other sets in
each of the treatment solutions.

3. Find the effective range of concentrations, pH, etc., and
give enough safety margin.

4. Find the working capacity of the solution.

5. Publish results.

EDTA is a very good start for research purpose, but I'm a bit
leery of adapting it to production work, because it is very
nondegradable and stay in the surface water for a VERY LONG
TIME, and it started to cause problems. If you dump EDTA into
sewer system, it goes right through the treatment plants and
gets dumped to the ocean. At least, EDTA solution should be
reused until it becomes ineffective, to minimize the quantity.

Ryuji Suzuki
"Strange how people who suffer together have stronger connections
than people who are most content." (Bob Dylan, Brownsville Girl, 1986)