RE: An exchange with Mike Ware (on Argyrotype)

Thanks for the contribution Ryuji.

-----Original Message-----
From: Ryuji Suzuki [mailto:rs@silvergrain.org]
Sent: 24 Mart 2006 Cuma 08:42
To: alt-photo-process-l@sask.usask.ca; mail@loris.medici.name
Cc: mike@mikeware.co.uk
Subject: Re: An exchange with Mike Ware (on Argyrotype)

Ryuji:
"The complexing effect of citric and other acids depending on the pH.
Relative effects between ligand-Fe(III) and ligand-Ag depend mostly on
the type of the ligand. If you want to make it most specific to
iron(III), I'd go for oxygen ligands, such as oxalic acid,
acetylacetone, gluconic acid, etc. and buffer at their optimal pH to
complex iron."

Loris:
Can you suggest a formula (most preferably using oxalic acid) that does
this job?

Ryuji:
"Another approach is to use compounds that make very insoluble complex
with silver to protect the image while using very powerful iron
chelating agent(s). For example, there are several substituted
tetrazoles, imidazole, etc. potentially usable for this purpose.
Benzotriazole may or may not work, but 1-phenyl-5-mercaptotetrazole is
pretty strong in its adsorption as well as having very small ksp with
silver."

Loris:
Well, I seriously doubt I will manage to find the compounds you mention
above.

Ryuji:
"One problem with residual iron is that it can generate hydroxyl radical
in presence of air and moisture, and this WILL attack silver image. To
solve this problem, it's most effective to incorporate iron ligand
chelator that inactivates iron's redox catalysis, a radical scavenger in
the paper base, or more preferrably both. Most effective ligands have
some affinity to silver."

Loris:
Can you please decrypt the above statements for us mortal non-chemists?
:) Which compound can do that job?

Ryuji:
"Regarding relative longevity of those nongelatin silver processes, it's
probably the best to run a peroxide fuming test with very low peroxide
concentration. (If you use a test condition used for toned
silver-gelatin prints, I expect the image to fade very fast and won't be
able to see any relative difference.)"

Can we use household 3% peroxide for this, or still need something
stronger?

Regards,
Loris.
Received on Fri Mar 24 06:35:41 2006