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 08:26:52 2006