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I remember
well the dismay of finding out that selenium toning was ineffective. Digital is far less labour intensive... although much less engaging. All round, digital is just too un-mysterious... too easy. Good for my commercial stuff certainly but missing the "Plastic" stage. It used to be that all 5 senses were involved... I long for the darkroom these days but the water out of the taps here is 35 deg. C and there's no place to buy any darkroom equipment or materials. karl shah-jenner wrote: from 2005 Robert : None of your references comes from Kodak. A fine point, but quite : important in my view. Lets look at your references: me: no you're right, it IS important.. and I am still dredging thu my references to find the specific site link .. As one researcher stated elsewhere "there is a very large literature on fixing and washing of photographic materials. Much of the research was done at Kodak Research Labs and is available in various scientific and technical journals. Kodak decided at the formation of the labs not to publish in a house organ but rather in established, peer-reviewed, journals. That made the research immediately respectable but has also made it somewhat scattered. Some publications, notably _Photographic Science and Engineering_ are rather hard to find. " But I finally found one, from Kodak, which acknowledges selenium toner was as I said, not adequate for protecting silver. The actual Kodak article I referred to at the time is still lost to me, and Kodak do not seem to have it.. nor would they really make a great effort to retain it since an admission that their product didn't do what it was claimed it would is hardly something a company would highlight. Nonetheless, it is clear from Kodak's article (and the NEW and IMPROVED product they had to sell in it's place) that selenium didn't do the job. Of course, they're still happy to market the product, after all, people buy it. http://graphics.kodak.com/docimaging/uploadedfiles/en_A1671.pdf "The Image Permanence Institute (IPI) at the Rochester Institute of Technology (RIT) in Rochester, New York, extensively researched redox blemishes in microfilms. IPI’s research showed that selenium toning did not effectively stop the spread of redox. IPI then looked at a polysulfide solution and Kodak Brown Toner solution in place of selenium. IPI’s testing showed both solutions stopped the migration of redox blemishes into the roll of microfilm. As a result of brown toning, toned microfilm has a higher resistance to the formation of redox blemishes. The combined use of brown toning and molecular sieves significantly enhances film longevity even under adverse conditions. " (again, adverse conditions is key - as I said before, anything can be archived - archiving is a storage process, not a production process) and another more relevant than the wishy washy Kodak article. http://palimpsest.stanford.edu/iada/ta95_123.pdf "In the mid 1980s selenium treatment was recommended for extending the stability of black and white film and prints in several publications [Lee et. al., (1984) and Drago et al., (1986)l. On this background all RC-prints and duplicate negatives were selenium treated at our department. Further research around 1990 showed that the selenium treatment (Kodak Rapid Selenium Toner, (KRST)) did not effectively protect the image silver specially in the low density areas of photographs [Reilly et al., (1989) 124-125 and Reilly et al., (1991), 101-1021" "Recommendations from Kodak concerning the use of Kodak Rapid Selenium Toner to protect the prints has varied" again, it came down to minute sulphide impurities in the early batches of selenium toner actually doing the protecting of the silver, later batches of greater purity removed the sulphide, and the subsequent protection that Kodak had used to market the product. "The test results .. indicate problems, specially in the highlights when using selenium to stabilise silver images. The results suggests that polysulfide treatment should be preferred to selenium. On the other hand selenium treated prints are generally found more attractive than polysulfide treated prints" regarding film treatment: "It can be concluded that treated films are more resistant to peroxide attack, but complete resistance with selenium calls for a more concentrated solution or longer treatment time (25 minutes!) than normally stated" this all leads to the statement: "Our conclusion so far is that all duplicate negatives made of historic negative cullections should be treated with IPI SilverLock, 1+50 for 3 minutes" and that's the thing - Silverlock is a sulphiding agent, not a seleniding agent. finally, a GREAT article from someone who actually cites the chemistry for a change rather than just talking about what someonhe else said: http://www.largeformatphotography.info/toning-permanence.html "Toning and Permanence of Silver Gelatin Prints By Douglas W. Nishimura, Image Permanence Institute, RIT" "everyone hears that bad processing is the root of all deterioration" .. "All of this issues were ignored and people only focussed on the poor processing. Hence, every photographer hears that bad processing is problem. You will find that finding examples of poor processing are not so easy to find. In fact, the major cause of deterioration is oxidation" " Fuji found that a small amount of residual fixer in their samples actually made them more resistant to oxidative attack. They weren't the first people to discover this. George Eaton told us that back in the 1960s, they found the same thing at Kodak, but didn't know how to tell people to wash well, but not too well" "There is nothing magic about microfilm silver (except that it tends to be very fine grained), but the chemistry that governs what happens to microfilm silver, also applies to paper " ("Microfilm was the first photographic material considered to have enough value that its deterioration warranted reseach funding and interest.") "When we brought this to Kodak, they tried to dig back in their records for formulations and chemical sources. They had run into something similar with regard to stabilization processed photographs. Prints produced by users in the field had unusually stable prints (quite resistant to oxidants), but when they tested the processors in the lab, they didn't find any high level of resistance to oxidants. It drove them crazy .. It was possible that selenium toner tested by Bard et al was an old bottle possibly contaminated with active sulfur compounds. However, we obtained a bottle of selenium toner from the same approximate time and tested it and got no better results. Kodak tried similar tests out and also found that the selenium wasn't working as well as it apparently did in the early 1980s and no one understands why." "we did find it interesting that the long-known solution of gold chloride and sodium thiocyanate (known as Kodak GP-1) worked pretty well. .. in the 1960s worked on a better formula that was to become known as GP-2. It consisted primarily of gold chloride and thiourea with a few other salts added. This formula really worked well on films and prints. Henn and Mack observed that as they increased the gold content of the solution, they observed no increase in the "protectiveness" of the solution, but as they increased the thiourea content, the treated film stability went way up. They didn't pursue the problem and simply decided to use five times as much thiourea as gold. So here we have pretty strong evidence that the thiourea complexing agent (that kept gold from falling out of solution) was contributing to the stabilizing effect of the toner. Gold solutions not containing active sulfur (such as GP-1) had no such effect if we varied the concentration of the complexing agent. " amazing really (the last bit) that they didn't 'pursue the problem'. It becomes really clear that the sulphide is the protective agent, yet they either didn't see it, or were not being very observant! "..you're forced to draw some conclusions about sulfur. .. Just a tiny amount of sulfur "dusted" on the surface of silver image particles can make the silver fairly stable against hydrogen peroxide oxidation, but for things like ozone and nitrogen oxides, actual conversion to silver sulfide is required. Selenium will work, but a heavier dose of toner is required in order to ensure that the mid-tones and high-lights are adequately protected." How about papers? Back in 1992 we had a Swiss Graduate student here doing his MFA here. The title of his thesis was On Black-And-White Paper Image-Stability Enhancement: Effectivenss of Toning Treatments on Silver Gelatin Prints Determined by the Hydrogen Peroxide Fuming Test. This 411-page thesis reached the same conclusions that we had regarding toners with film. " it's been a long time tracking this down, but it' something that bothered me . karl |
