Stability of Black and White Photographic Images

[dancqu]

This thread's title with quotes pre and post, entered
via Google, will lead to an Abbey Newsletter. I doubt
my hot link will work.

Some issue has been made as to toning with sodium
sulfide so this pointer. Although much of the article is
very technical and detailed a substantial portion is in
plain english. Material specific to micro film is present.

The introduction through Early History is of general
interest. Scroll down about 2/3 of the article to where
Selenium Without .... will be found. Pick and choose
from there to bottom material of interest.

The emphasis off and on is with microfilm. I have read
more than once that microfilm and print emulsion image
structures are very similar. They are both fine grain
silver gelatin images. Comment. Dan

palimpsest.stanford.edu/byorg/abbey/an/an12/an12-5/an12-507.html - 37k -

 

[Photo Engineer]

Dan;

Prints on paper suffer from less sharpness due to internal reflections. At normal viewing distance you cannot see the sharpness difference.

OTOH, microfilm is maximized for sharpness via fine grained emulsions AH layers and acutance dyes.

They are both hoped to be stable, but for different reasons.

PE

 

[Ryuji]

First, try this: http://tinyurl.com/zsvop

There are several researches on this topic by IPI, european groups and testing run by myself. There are some speculations on the possible changes in the formulation of KRST (search for the old pure-silver list) but I now think the real reason is elsewhere.

There are a number of reports from early 1980s and earlier, proving dilute KRST treatment was completely effective with microfilm of that time. But later 1980s the same treatment was not as reliable as the older tests, again, with the emulsion of late 1980s and 90s.

There are two differences I see in these studies. One is that the standard condition for accelerated testing became harsher and harsher. Many early tests were run at 100ppm or 500ppm peroxide. Recent ones are run with 1000ppm or sometimes 3000ppm or even higher. Samples are usually incubated in a constant humidity and temperature for several hours to days. So, one possible difference is that, something that was effective against 100ppm peroxide is now ineffective against 1000ppm peroxide.

Another difference is in the way emulsion is made. During 1980s, commercial emulsion production methods saw a lot of technological advancement. Microfilm emulsions, being slow, high contrast and requires high resolution, were the first product category to apply a lot of new technologies, such as tabular grain emulsion. The frist group of t-grain products were released around 1983, including Kodacolor VX-1000, medical X-ray film, and microfilm (all Eastman products).

I think both of these difference gave rise to apparently contradicting results from early and late 80s to 90s.

I have run some tests with AGFA MCC, AGFA MCP and Forte Fortezo papers using 3000ppm peroxide concentration. Polysulfide treated prints were most resistant to peroxide attacks across the density range, from light to dark.

Some published tests included enlarging papers. One was the work at Smithsonian, another was the work of Harald Sorgen at University of Applied Sciences Koln. Maybe there are more if I look up my file. The reason why microfilm was studied is because of the availability of research funding and perhaps other factors.

Anyway, it's not that selenium is not effective at all. It is somewhat effective but not as effective as polysulfide.

 

[Photo Engineer]

I think one must consider reciprocity failure in all accelerated stability tests. Chemical reciprocity will cause odd effects if concentrations are increased to high levels and/or temperature and humidity are part of the test.

That is why the true test is whether the photograph is still around in X years, not how they withstand Y hours at high temperature immersed in an atmosphere of peroxides. (BTW, Hydrogen Sulfide gas is also used as well as carbon dioxide and sulfur dioxide, as they are some contaminants present.)

As part of Kodak's actual test, they have a room that is devoted to light stability covering one floor of 1 building. The photographic products are allowed to age naturally in daylight, and are then compared to the accelerated tests when the natural aging is done. This test takes years to accomplish.

PE

 

[DKT]

I think the reason why it was about microfilm, was because of some deterioration problems they found in various archives around the country back at that time. microfilm has been the format for long term records use in this country, since I guess about the 50s. They use it for storage & dissemination of all sorts of records, newspapers, old books etc. not only is there a huge amount in archives all over the place, but it is also the longterm storage medium. the reason why you find those reports on the various conservation sites, is mostly because they're dealing with the archivists & preservation managers that work with the reformatting projects. the projects are pretty big in terms of preservation. much larger than anything using other photo materials. so, I think that's why the money was available and put towards the research as well. makes sense really, if you think about it.

 

[Photo Engineer]

DKT;

I agree, but I have seen some microfilm that was processed in pretty miserable conditions and wondered to myself how well they would survive. At this point, in most cases, no one knows how well they were actually processed.

In other cases the film was casually stored at local libraries under ambient conditions.

OTOH, I have seen films stand up very well after careful treatment and storage at George Eastman House.

PE

 

[DKT]

PE--I don't know, I don't work with those programs. the agency I work for does have a microfilm lab, and I know they do a lot not just archiving the records , but also smaller local gov't as well-either send their stuff to get reformatted or they act as an advisor for outsourcing the stuff to vendors. The projects aren't limited to records entirely, they run through newspapers, books etc. They do have a published set of guidelines that outline the QC checks & procedures though, and it's all in accordance with the ansi/iso standards. these projects, are sometimes funded from the Federal level though, as are a lot of the preservation surveys etc--they have to meet certain standards. I don't think there's much leeway really with this stuff. the QC checks cover optical & physical issues as well as the processing, including methylene blue tests, and then storage & access (master & surrogate).

I do know that the microfilm programs are huge compared to other types of "archival" imaging using analog materials. I think it will be the last format left to be honest, because there's a lot of digital being used in the place where sheet film, b&w rollfilm, and papers were used in the past. these programs all revolve the LE of microfilm, and everything else is compared to that. I think the reason why film is still being used at all, is because of microfilm. This is just my personal opinion mind you, but there's a big change going on right now in terms of imaging (as you know), and the microfilm programs seem to be pretty steady, not to menton the talk of archiving computer files to microfilm. I don't think it's going anywhere, the rest of us probably are going digital in terms of "archiving", but not those programs.

'course even at home--these are my opinions only.