Ryuji said:
I have been presenting the chemical mechanisms and also referring to IPI research which confirmed that double strength of Sistan can expedite image deterioration compared to untreated image. All of these sum up to the conclusion that Sistan is not as good as image protecting agent should be.
Your basis to support Sistan is pretty weak: a single report from Ctein (who apparently didn't test anything but the recommended usage of Sistan). What Ctein showed is that Sistan treatment was sufficient to prevent one particular aspect of oxidative degradation at his condition.
The goal of testing for archival processing and image permanence should be to test the material at sufficiently harsh conditions to ensure good survival of the image at all reasonable storage conditions. Ctein's test was specifically designed to make it harsh for RC paper. It is insufficient to conclude general overall efficacy of Sistan treatment, and it is also insufficient in terms of robustness of the treatment efficacy.
How many Sistan users do you think would worry enough to run standard peroxide and bleach test? I've run these tests on Sistan-treated prints as well as prints treated by other means, and I have first hand experience as well as knowledge on the chemistry of these processing. I also follow publications in scientific as well as technical journals and patents on this issue as well as many areas of photography.
I understand with your presenting these mechanisms and keeping up to date with publications.
I merely point out that first, the 'wisdom' accepted at EK when I worked on image stability was that chemical tests were unreliable. Accelerated heat and light tests were reliable.
Also, Ctein's tests were done with natural keeping using light not chemicals. Due to his professional method of testing, and his incentive for solving this problem as best he could, I trust his answer.
I'm not saying one is better than the other, just that our accpted practices at EK at that time correspond roughly to Ctein's tests and that the tests using light and heat rather than chemicals were quite reliable. The accelerated EK tests using light, heat and humidity worked well compared to actual samples kept for 20 or more years. And, these tests were concieved years before there was an external standard that you have cited.
In point of fact, B&W image stability has been well characterized for nearly 100 years and is elaborated on by Haist. It boils down to this, you must retain just a small quantity of sulfur compounds in your print. Too little or too much leads to image degradation, and Ctein's work has indicated the same thing. Image stability of B&W had a resurgance in importance with the introduction of RC, as the stability of the RC support and the images thereon changed due to the fact that the coatings washed more completely changing the levels of retained sulfur compounds and altering image stability. Adding TiO2 and the other chemicals to the equation further complicated issues.
These issues, BTW, applied to some extent to color as well.
In any event, much more was done at EK that was never published than was published, and I'm sure this was so at Agfa during the development of Sistan. I am in no position to suggest that the use of Sistan is useless in the face of evidence that shows otherwise. Used properly it will work, but used improperly it will either not work or harm prints. Our goal is to use every chemical properly. Used improperly, any photographic chemical can ruin otherwise good negatives or prints, therefore I see no problems at all with Sistan provided the instructions are followed. Used outside of those limits, I see no reason to disagree with your asessment either, that it can be harmful.
Hundreds of reports exist internally at EK concerning image stability and hundreds of patents exist on stabilizing both B&W and color images. The internal reports, as noted above, are never released outside of Kodak and the same is true of Fuji and Agfa among others.
Now, Fuji has ceased production of their stabilzer citing the difficulty or expense of manufacture, and yet you say it is rather easy to make. If this is so, as someone asked above, why are they really stopping production? That is a rhetorical question. I really don't care. It is a fact that we cannot change. I'm sure that with proper testing we might find that the Fuji compound also has 'loopholes' in stability.
And that is my final point here. There are compromises and loopholes in all practical applications of chemical solutions to image stability and in testing image stability. I've pointed some of each of them out above. So, knowing theory and running a few tests is quite useful, but not broadly revealing. It is when you have a roomful of people who have run thousands of tests, and you statistically compare results that a picture begins to emerge. That is where the corporate approach has benefit for the average photo artist and hobbyist.
In fact, I have found based on a single image stabilty test that something was worse, but statisticaly it was better, but had a higher variation. So, a single test was useless. I have found that theory predicted one thing, but practice gave a different result over a number of trials, and I had to accept practice over theory. Again, a single test was useless.
Due to this, I find that repeated statistical tests are the most useful, and that if practice overrules theory, the theory may still be correct but I have to accept what results from practice.
PE
