what causes bronzing degradation of a silver print?
I have a couple of prints on my wall that have started to degrade, I only noticed it when looking closely (cleaning the frames). They've started getting a reflective (the metamerism is what I noticed first) bronze appearance in the shadows/lower-midtones. It's uniform across the print (not just the edges) but definitely correlates with the denser parts. A couple of Zone-III regions have it speckled across them, and it forms dense lines of reflectivity where light & dark parts of the print meet. The darkest regions don't seem to have it and the higher zones are clear. It has a bronze appearance in diffuse light and a silvery appearance from straight-on - see attached.
The paper is Arista.EDU RC VC gloss, aka Foma Variant, developed in Ilford Multigrade 1+7, fixed for 1:00 in Hypam 1+4, washed for 4:00 (continuous agitation) with 6 changes of water. The change has occurred only (and equally) in two framed prints and other prints made in the same timeframe and stored in paper boxes have mostly not degraded; one (of maybe 20 in boxes) has bronzing over about 1/3 of its area, seemingly where it was more exposed to atmosphere. The prints are only about 20 months old. The framed prints are sandwiched between acid-free mat boards and behind glass. Not hermetically sealed. They're hung in a bedroom out of direct sunlight and the humidity is often very high due to drying clothes in front of a heater (we can get condensation on the windows) but there has never been condensation in the frames.
Being in Adelaide, I have a fair bit of iron in my process water, could that be a cause? Perhaps I have humidity-induced silver-mirroring and colouring of that due to iron?
What is the degradation and how do I avoid it? Is my portfolio of stuff printed so far mostly screwed?
Incomplete fixing and washing is at the top of the list.
Mark Barendt, Beaverton, OR
"We do not see things the way they are. We see things the way we are." Anaïs Nin
I think I fix for longer using bath A and B (I use plain hypo 3-4 minutes in each) and use hypo clear per Kodaks instructions.
The hypo clear is cheap... and RC is more expensive than hypo.
If your locality is very industrial that can be a problem my mum 'lost' her silver plated cutlery over several decades.
If you need archival consider toning...
I would agree with markbarendt. Are you using a single fixing bath? Two is more reliable.
This print was single-bath fixed. Note that this is RC paper not FB and I'm using fixer at film-strength not paper-strength. I am therefore fixing for twice as long, or at twice the concentration as recommended by Ilford in their Hypam datasheet. I also process at 25C not 20C, so that should also dramatically increase the fixer reaction rate.
Likewise the wash, Ilford recommends 2 minutes at 5C or higher, I do 4 minutes at 25C. Again, twice the recommendation ought to be safe!
As to excess silver in solution, I use the fixer to about 1/2 its rated capacity (40 of 8x10 per L of working solution), so the silver concentration should be under 2g/L. Maybe the Foma paper is more silver-heavy than Ilford's RC offerings, but I doubt that it should be dramatically so. And if it were, then I would expect highlight yellowing due to the creation of sulfides in non-image areas, but that's not happening.
I had a read of this guide, which has this to say about underfixing/underwashing (emphasis mine):
I have the opposite problem: silvering, and totally clear non-image/highlight areas. I would go with silver-mirroring, except that the mirroring doesn't extend to the deepest shadows, it seems confined to the lower midtones. I have been abusing the prints with high and variable humidity, which can cause mirroring.
Faulty processing results in silver-fixer compounds remaining in the print after processing. This can be the result of not enough time in the fixing bath, exhausted fixer, or not enough washing. The results are not immediately visible, but over time the fixer (sodium thiosulfate) breaks down and reacts with the silver to form small particles of yellow silver sulfide across the entire print. This weak yellow staining is generally only visible in the non-image areas and highlights
, while in the midtones and shadows it is masked by the silver image. The residual fixer will decompose and react with the silver image, causing yellow/brown discoloration of the image in the highlights and midtones. If faulty processing is the cause of discoloration, silver-mirroring will likely not be seen
, since the sulfur in the print reacts quickly with the silver ions, preventing their passage to the print surface
The PDF also talks of sulfide stains (from post-wash contamination), but they don't seem image-related: the examples are a fingerprint and a liquid mark. The effects in my prints correlate with the image structure, not fingerprints or blobs spilled thereon.
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not sure if bronzing is the same as silvering out but
Does it look anything like the images in this report: http://iaq.dk/image/rc_photos.htm
Originally Posted by polyglot
Very interesting, thankyou. Does anyone have an example of what this "silvering out" looks like? And what constitutes "gross overwashing"?
Originally Posted by jnanian
No, the highlights are all completely clear. No yellowing except where it looks like image-silver has been ion-migrating and then both sulfiding and plating out in a mirror.
Originally Posted by paul_c5x4
hard to explain what silvering out looks like
kind of like the print has metal on the surface of it that
has tarnished. when tilted to the side it has a metallic-sheen to it.
and with regards to grossly over washing ...
according to pe you need to do a residual hypo test to see when it
"passes" and when it does, stop washing ...
if you have ag stab, you can use that to stabilize the rc prints
it is the same as sistan ( i think it is the same as sistan )
or use selenium toner to tone your rc prints ...
were your prints in frames ? i have heard that rc prints out-gas which also
causes problems ...
Last edited by jnanian; 07-01-2014 at 07:30 AM. Click to view previous post history.