Re: Another Ziatype question

From: Sandy King <sanking@CLEMSON.EDU>
Subject: Re: Another Ziatype question
Date: Mon, 11 Oct 2004 13:50:26 -0400

> Have you checked the pH of your developer? Staining that can not be
> cleared results from the formation of iron hydroxide from residual
> ferrous iron, Fe(2+) in an alkaline environment. In kallitype
> printing staining can take place during both development, if the
> developer is alkaline, or during washing, if the tap water is too
> alkaline. The iron content of the tap water, in combination with a
> high pH, may also play a role. I suspect that the same goes for
> Pt./Pd. printing since residual ferrous iron is a reduction
> by--product.

I don't practice those processes myself, but I can add a bit about
iron chemistry.

Unless the solution contains reducing agents, Fe(II) ions are
converted to Fe(III) in neutral to alkaline pH, and make ferric
hydroxide like you mentioned. If the intention is removal of iron, it
is best you don't let this happen. I would try acid DTPA or EDTA
solution to facilitate removal of iron.

--
Ryuji Suzuki
"You have to realize that junk is not the problem in and of itself.
Junk is the symptom, not the problem."
(Bob Dylan 1971; source: No Direction Home by Robert Shelton)