RE: Iron

Ryuji, Does the reading that you have done then suggest that use of an EDTA
clearing bath would not good? One reason that I switched to using it years
ago, was that it left the paper feeling better. The acid washed paper felt
stiff or brittle. Which is worse for paper, residual acid or iron? Both? And
is it a specific EDTA? I have started with di sodium for bath 1 and then
switch to tetra as the clearing proceeds. Would a pH change slow the iron
from reacting?

Eric Neilsen Photography
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> -----Original Message-----
> From: Ryuji Suzuki [mailto:rs@silvergrain.org]
> Sent: Monday, March 27, 2006 8:20 AM
> To: alt-photo list
> Subject: RE: Iron
>
> On Mon, 27 Mar 2006 11:48:39 +0300, "Loris Medici"
> <mail@loris.medici.name> said:
>
> > In the light of the previous exchange, I believe residual iron is a real
> > and serious problem for iron-silver processes.
>
> I agree iron can be a problem, but I would want to compare what level of
> iron is detrimental to paper and what level of iron is found in
> traditionally processed iron-silver prints. It is probably that the
> aging of paper is accelerated by any amount of iron in rather
> dose-dependent manner. If this is the case, we want to get some idea of
> what amount of iron impregnation that would not significantly shorten
> the life of paper compared to non-impregnated paper, and aim that value
> as the archival standard for the processing of iron-silver processes.
> However, I have no idea what that level would be, at all.
>
> > Actually, that was another person's question. My understanding was since
> > iron is a strong catalyst for silver oxidation + a catalyst won't
> > exhaust, even a small amnt. is not tolerable. This is not an absolute
> > fact, it's my (maybe completely wrong) personal take. I hope future
> > messages on this issue will clear that for us (including me).
>
> Iron catalyst won't be exhausted by the mechanism described in the web
> page in yesterday's post and a few other review papers I managed to get
> last night. This is typical of iron catalyzed oxidation seen in many
> places. I've also seen a research that showed that EDTA treatment of
> iron-gall inked paper worsened its keeping property, which is consistent
> with the idea that iron is acting as the catalyst.
>
> Users of iron-silver processes should be concerned about 2 issues.
>
> 1. degradation of silver image due to environmental pollutants
> 2. degradation of silver image and paper substrate due to iron
>
> For 1, I think the best method is to use noble metal toning or use Fuji
> Ag Guard.
> For 2, I think the best method is to modify the process to ensure
> thorough removal of iron and then treat the paper with something that
> inactivates iron's catalyst action and also act as an antioxidant.
>
> In these, we are concenrned about easier problems than those
> ink-corroded paper conservators because the treatment is applied at the
> time of creating the work. Much of the problems in paper conservation
> seems to be related to the fact that most useful treatments being
> water-based, change of color or strength of the ink, and volume
> processing of the material.
>
> However, before any treatment is justified, I think there are two points
> that need to be demonstrated: 1. a problem exists. 2. the problem can be
> solved by the treatment without any adverse effect.
Received on Mon Mar 27 09:50:34 2006