Metallic sheen on old prints

Over the weekend, I started digging through my old negatives to start a Grand Reorganization project. I noticed that some of my ~30 year old contact sheets have that metallic sheen/glaze look. What causes that? Is it under-fixing, or something else?

(I'm hardly surprised. I was pretty lax back then and even moreso on contact sheets.)

It's called bronzing. I forget the exact causes. It used to be quite common on framed photos done on RC paper of around that era. Some kind of light activated reaction with the TiO2 whitener in the paper in that case, but it can happen in other ways.

I've heard it called "silvering out". It's definitely due to poor fixing and/or washing. I had a couple of prints tacked onto my kitchen cabinets that get full sun on them for a good part of the day. These prints started to go that way after a couple of months. They were RC prints, and I know that I wasn't careful about fixing and washing them. I've never seen it with FB papers, but I'm sure it can happen. I have RC prints that are very old, but have been properly fixed and washed that do not exhibit this, so don't take this as a suggestion that RC papers are inherently inferior. I don't think they are.

See this link for some in depth information about bronzing:

James M. Reilly - Care and indentification of 19th century photographic prints

In addition, there is some info in this interesting document:

Photographs from the 19th century, a process identification guide by William E. Leyshon

Marco

I'm fairly sure Frank is right... inadequate fixing.

As said above TiO2 can mobilize metallic silver in an unstabilized PE Paper due to its photocatalytic action.

nworth said:

Some kind of light activated reaction with the TiO2 whitener in the paper in that case, but it can happen in other ways.

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One other fast way for bronzing is almost exhausted thiocarbamide / thiourea sepia toner.

I have seen a metallic sheen turn up in prints that I toned using a two bath ferricyanide bleach followed by redevelopment in thiourea, where the second toning bath was at the end of its life. If the toning times go upwards from maybe a minute or two to ten, than its not only time to ditch the toner, but in these particular situations, I have seen bronzing appear on prints after drying, especially in the darkest regions of the print.

Please note that this toner also contained sodiumhydroxide next to thiourea in the redevelopment bath (you can tone without that as well, resulting in more yellow sepia tone, while with sodiumhydroxide, the tones are more reddish brown sepia).

NOTE: this was on FB, not RC!, paper.

Marco

Marco, the exhausted thiourea toner scenario is equivalent to improper fixation. The potassium ferricyanide + potassium bromide bleach will turn metallic silver to silver bromide. If it's not redeveloped fully in the toner, some of them will be left. Insufficient fixation has the same effect.

Anon Ymous said:

Marco, the exhausted thiourea toner scenario is equivalent to improper fixation. The potassium ferricyanide + potassium bromide bleach will turn metallic silver to silver bromide. If it's not redeveloped fully in the toner, some of them will be left. Insufficient fixation has the same effect.

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Yes, I was aware of this, although to correct or better said supplement what you write: part of the silver is also converted to a silverferro/ferricyanide complex, which is a rather stable complex, even under light, not silver bromide. Just watch what happens if you throw a bleached image in fixer, not all of the bleached image will disappear.

This remaining complex is really quite stable, probably similar to a cyanotype, which forms a similar complex. I have two results of in this case partially bleached and subsequently fixed images (so NO thiourea toning!) that are now hanging in a friends house, and after two years, they still look exactly as when I finished them in the fixer. The yellowish complex (next to remaining black silver as I partially bleached and deliberately overexposed the paper quite strongly before bleaching), gives a really nice atmosphere to these images, a bit like lith images.

Some good info can be found in this nice document by Wilco Oelen:

http://www.woelen.nl/photo/toner.pdf

Another interesting point is that that bronzing was on images that I refixed after toning using fresh fixer! I started doing this with all my sepia toned images, after reading some more and Tim Rudmans advice.

I only noticed the metallic sheen after drying of the print. But it may be that the bronzing and printing out already occurred before fixing, although I still think some other factors are in play in this particular case of exhausted thiourea baths, as why would the bronzing occur so fast as to affect the image even in the short time up to the fixing? No real reason for that, as otherwise ALL bleached images would suffer from that.

Marco, thanks for the pdf, interesting stuff. Regarding the metallic sheen, I find it quite strange, given the fact that I've never seen it happening with the stinky sulfide (Na2S) toner. I don't think it's a case of "print-out", I've never done sepia toning under safelight conditions. Could it be inadequate washing after, or between the toning phases?

It also happens on old film and fiber prints. I worked for a museum exhibit preparation service, and once worked on a vast negative archive (70,000 negs from the same photorapher), most from the teens through the '30s. I had to catalog them, describe them, pick worthwhile ones, restore them if needed, and then digitize them (high-rez digital camera with a macro lens on a lightbox). Many of the sheet negs, though kept in glassine envelopes all those years, had developed this problem, mostly around the edges. We used metal polish (the kind built into the cotton), and left the residue in place. It worked like a charm. Lots of light applications did the trick for the damaged negs. For prints with the same problem, it was a three-step process. We used the polish, then rinsed it off in an acetone bath. Then, if any ink from the back of the prints showed through after the acetone bath, we would bleach it out using a special method...AKA taking the prints up to the roof and putting them in the sun while sitting in a tank of water. Everything turned out great. They had spent a lot of time coming up with these ingenious methods before I ever worked there, so I did not argue.

At the same job, I got to personally handle the transparencies or one of my favorite photographers; Ernt Haas, and to learn Ilfochrome printing when prints were ordered. It was quite a job!

Anon Ymous said:

Marco, thanks for the pdf, interesting stuff. Regarding the metallic sheen, I find it quite strange, given the fact that I've never seen it happening with the stinky sulfide (Na2S) toner. I don't think it's a case of "print-out", I've never done sepia toning under safelight conditions. Could it be inadequate washing after, or between the toning phases?

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Stinky sulfide toner is definitely different from a two bath bleach sepia toner. Although I have no real prove for it, reading Wilco's articles has pretty much convinced me that that part of the silver being converted to that silverferro/ferricyanide complex, actually for a large part remains in a sepia toned image, even after the redevelopment in the thiourea. This is not a real problem, as it is very stable too.

It is probably one of the reasons that smelly stinky (Na2S) toner is supposed to give deeper / darker browns, as that remaining complex of silverferro/ferricyanide in a two bath sepia toner, the yellowish component, simply remains and holds back the darkest possible brown tones of the image.

So, contrary to a Na2S toner, probably not all bleached silver is converted to Ag2S.

By the way, I do not tone under safelight conditions, maybe I should, but I haven't seen any detrimental effects or metallic sheening in any of my sepia toned images, except the ones that were redeveloped in a thiourea bath close to exhaustion, something I try to avoid nowadays.

Another interesting discussion by Wilco Oelen can be found here, in which he also did a permanence test of his novel Vanadium green toner, see the last post:

http://www.photography-forums.com/new-vanadium-toner-t92162.html

In addition, it seems Wilco truly devised a new and better type of green toner, since as he describes, most others are based on rather expensive, difficult to find, and unstable forms of Vanadium.

But I would be interested to read Tim Rudmans comments about the toner as suggested by Wilco.

But we are getting a bit off-topic here

More interesting info about toners and developers by Wilco Oelen here on his page:
http://81.207.88.128/science/photo/index.html

And a small discussion about the different types of sulfide toners, that mentiones the difference between the single bath Polysulfide toners, and two bath bleach / redevelop sepia toners:
http://81.207.88.128/science/photo/toners/sulfide.html

By the way, Anon Ymous, when you mentioned you used a Na2S toner, did you mean you use a one bath "Polysulfide" toner as described in the above link, or the "The plain sulfide toner, with its characteristic bad rotten egg smell" as described there also, but still requiring a bleaching step???

I know realize my last post may have been incorrect. If your Na2S is the kind of toner also needing a bleach step, than it probably does not give darker tones than the thiourea based toner I use, because that remark related to the Polysulfide single bath toner.

And a discussion about the chemistry of developers:
http://81.207.88.128/science/photo/developers/index.html

Marco

Marco, when I was talking about Na2S toner, it was about indirect bleach/redevelopment toners, like the Kodak Sepia Toner (the only one available locally). All bleaching/toning was done at the balcony, but not under direct sunlight. I had no problems whatsoever.

Anyway, Wolfgang Moersch has written some articles about sulfur toning (part 1 is here). At some point he states:

All thiourea toners are highly alkaline! Fresh solutions start toning abruptly. It is an early sign of exhaustion of the toner, if the print is not fully toned after 30 seconds. Instead of extending toning times to one minute and above, you should regenerate with alkali.

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(Yes, we've gone off topic.)

EDIT: Click the British flag to get the English version of the article.