It's also been written about quite a bit on the conservators/archives list run off CoOL. One or two of the researchers at the Image Permanence Institute belong to that list and have posted about this...it's also written up in an issue of the Abbey Newsletter--from the early 1990s, in an article that deals with microfilm deterioration. I would post a link to it, but it's all copywritten material--at any rate, if you go to Conservation OnLine and search the Conservation DistList or do a general search of the site, you can probably find similar articles. I think it's more complicated than just having some residual fix left in the material--my understanding from reading this stuff was that Kodak and some of the other manufacturers realized this going back 30-40 yrs ago, but couldn't come up with a quantifiable measure for how much should be retained. Douglas Nishimura (hope I spelled that right) from the IPI has written the most about this on the DistList. You can search by the year or the author.
hope this helps, KT
Thanks for the information guys. I will look into this because it flies in the face of everything that I have ever heard. But then again, life is ever evolving. Thanks again.
go to the Consdistlist archives--you can get to this at the bottom of the CoOL opening page. look under search by author, and find Nimishura's post--there are several that deal with this topic, but they're hidden in other postings...I did a quickie search & found it in 9/21/97 "processing RC papers"...if you go to the Abbey Newsletter--look at Vol. 12 no. 5/ june 1988. "Stability of B&W Photographic Images with special Reference to Microfilm". Somewhere on the Distlist is another version of this same tech paper, I used to get this list at work but email got all fouled up & I lost track of it....I think the state archives nearby uses a methylene blue dye test for residual fix. You can find about these tests on CoOL as well. You probably wonder why all this is about microfilm, but that's what most of these archives use for longterm records storage and it's sorta the standard that other materials are put up against. At any rate, these are worth reading, but probably won't change the way alot of people process...
I wonder at the comparison of microfilm and RC paper to fiber based paper. I can certainly understand that image degradation may not be as pertinant to a plastic substrate. Fiber would appear to be another matter entirely.
No, actually image degradation is probably more an issue for a plastic based material than a fiber base one for number of reasons. For one thing, microfilm is the standard in archives for longterm records retention and preservation reformatting. Fiber based papers are used to make archival prints for some types of projects like a building survey or whatever reason, but microfilm is what other materials are compared against. If it's done to the standards--this includes type of film, process and storage--it's LE rated (life expectancy--they don't use the term archival) for 500 yrs. Polyester based films are very stable and don't require the lower temps that the acetate films have. My guess is a fiber base paper would be maybe 100 yrs or less, but it would depend heavily on how it was stored. Paper isn't going to be as stable as a polyester support because of temp & rh and handling. Same goes for an RC paper. If the paper itself didn't self-destruct from say the dev-inc. agents, or the brighteners, or preservatives-- if it was stored in a climate controlled vault it could be considered "archival"--might be a hard concept for some to accept, but it comes down to the storage environment in the end. You can spend all sorts of money on archival processing & enclosures, but if the environment isn't right, it won't mean much in the long run.
All these materials are different because of base supports--but the thing in common is silver halide emulsions. Silver is silver. It might be that microfilm is finer grain, and has a tighter pattern for the emulsion, and is more sensitive--I don't know really, I'm a photographer--I'm not a conservator, an archivist or a materials engineer....But I do know that microfilm is the standard for archives. They have a whole set of ANSI/ISO standards that they check against. These include filming & storage--from enclosures & handling to temp & relative humidity. We follow similar stds. where I work for storage of objects--to keep our AAM accredidation, and I can tell you that the criteria would be almost impossible to do outside of a temp controlled facility or vault. It's really hard to do even in a facility designed for this purpose...you pretty much have to put things away forever, or view them for short periods of time without committing the unforgiveable act of touching them, and use uncomfortable temps & rh's and lighting.
So what you have is a bunch of archives around the country that discover problems with their microfilm collections over a span of a decade or so. They study it, and come with these recommendations--which include a change in the way the film is toned & post-treated. They also begin to review the standards for storage...but this also includes regular film & photogaphic images in general. You won't find many studies out there of photos in the "real world". There are no set standards being followed for the most part. Alot of funding for institutions is contingent on these accredidations and being able to follow these standards. It's what defines a professional institution. But what this means is pretty much putting images away in dark rooms, or in cold vaults away from anyone ever seeing them--and displaying copies or using "surrogates". The prints are treated as artifacts or master images with duplicates used. It's just different...they're looked at as records, not so much art. Outside--people process film to their own made up standards, they display & handle them however they see fit. Nobody can predict how long anything will last, not even a manufacturer, without some control to go against. You couldn't find a bigger test pool than microfilm in archives....
There's a theory that rc paper is more sensitive to pollutants than fiber because the emulsion is lying on top of the support. the base traps pollutants and they can attack the image from both sides. With fiber , the theory goes, it allows pollutants to pass through and the damage is slower. So, it could be a big deal--depends on what you're doing I guess. Where I work, we're film based for longterm, so it's of interest to me and I pretty much believe it's all the same in the end...
Camera and Darkroom had an extensive analyis of RC paper and compared it to "Fiber -Based" (actually not true - both RC and "Fibre" can have a paper fiber "support" - a *few* RC papers are consrtucted with a plasitic - Polyethethelene? - core). Both papers have emulsions that "Lie on top of the base"... and the "base" in both cases lies on top of the support - the difference is in the polyethelene encapsulation of the "support" of RC papers...Being impervious to chemicals and water itself, washing and drying times- and curling - are drastically reduced.
Base materials are different - "Fiber" papers use "baryta" - a white clay: RC uses Titatnium Oxide - a pigment used widely in white paint.
Its hard to envision RC emulsions and bases "trapping" pollutants - where they "soak" into the fiber support with no PE encapsulation, it seems to me that they would hang around considerably longer and have a more pronounced effect on image degradation.
they have a paper core with back & front layers of polyethylene. They're not entirely encapsulated though, so this is how chemistry can enter the sides of the paper by prolonged wet time (the paper can become delaminated from excess wet time or mishandling. Chemicals can get into the base and not be removed easily and can cause stains later on. they're not so impervious to heat & humidity either. They can still curl & flex with cycling conditions and when it comes to processing--they can burn up & melt in dryers or get a mottled/hazy look from low heat or air drying).....the emulsion is coated on top of the plastic. If you want to read theories & what-if's about RC papers--look at Henry Wilhelm's book a bit where he theorizes that if a RC paper were made on an opaque melinex (polyester) base like a Cibachrome, that this would be a more stable material than a fiber base paper...it would be like a b&w version of a cibachrome, that could toned for protection. At any rate, polyester is a better material, but is more expensive--polyethylene is cheap.
Here, I did some homework for y'all, I thought maybe you'd maybe just go dig this out yourselves, but there are alot of things like this out there--you could also try the archivist listgroups (look on Archives-L) or the conservators that deal with indoor air pollution. As far as I know, these posts are all copyrighted to the ConsDistlist authors, so I'm going to sort of point in that direction.
oh well, read these, dig around & form your own conclusion. --my opinions only as always--KT
One of the pitfalls of writing here is to try to determine the proper "depth" of a reply. I try to get the point across as simply as possible, and that leaves a lot open to "yeah ... but that is not the whole story". True, the edges of a paper with a fiber support (trying to use the same nomenclature as the original message - "core" seems more descriptive) ARE succeptable to capillary action - "sucking up into" of liquids ... as they are not sealed.
Is the emulsion truly "on top of the plastic, or is it properly "on top of a layer of Titanium Oxide" - which is desirable for a "bright white" and "uniformly white" background for the emulsion?
In any event, the point I was trying to make was that, considering the construction or RC papers, the idea that they are less archival than "Fiber Papers" because they entrap pollutants does not seem to make much sense.
Mylar cored - or PE cored - papers would be even better - the big drawback here is cost. Ilford produces an Ilfocolor "Deluxe" - or something that sounds like that - with a plastic core - I've used it - interesting stuff - it reminds one of a sheet of metal - and I like it a LOT, but it costs something like three times as much as regular (fiber-cored) Ilfocolor - the stuff I use for nearly all of my color printing.
Go to Abbey Newsletter, Vol. 21 no. 4, Nov. 1997. "How Stable are Photos on RC Paper" by Douglas Nishimura, IPI. This is pretty similar to his post on the Distlist, but contains some more info about ANSI recommendations for storage and a little more about the polyethylene base.
Like I said, read this stuff--there's a ton of material on CoOL and links to dozens of other sites as well. KT
Is the emulsion truly "on top of the plastic, or is it properly "on top of a layer of Titanium Oxide" - which is desirable for a "bright white" and "uniformly white" background for the emulsion?<<<<
>>>Mylar cored - or PE cored - papers would be even better - the big drawback here is cost. Ilford produces an Ilfocolor "Deluxe" - or something that sounds like that - with a plastic core - I've used it - interesting stuff - it reminds one of a sheet of metal - and I like it a LOT, but it costs something like three times as much as regular (fiber-cored) Ilfocolor - the stuff I use for nearly all of my color printing.[/quote]
BTW-- this is sorta what threw me here in your post--before I spun off into the standard archives rant I seem to be afflicted with--must be poor morale or something.....
PE cored would be polyethylene--not Mylar which is polyester. Polyester is a better plastic, very stable and hard to tear/cut. If you look at film-- alot of roll films are on acetate or some variation of it, and this base can shrink with age actually-- it buckles the emulsion right up off the base. It can lose like 10-15% of it's size as it degrades. The average lifespan for a roll of b&w film in normal conditions is only about 50 yrs or so, but for the polyester based films (mostly sheets), it's much longer because the plastic is more stable. This is why it's used in microfilm...the other worry is then the emulsion--and this is why they use sulfide toners. In a preservation project, they make a "master" copy and then use dupes, or "surrogates". The master is never really used, but kept in a cool/cold vault or other type of room.
But polyethylene is a cheap plastic-- a ciba (classic) was on some sort of solid white melinex base, so the theory was that if a b&w paper were made like this it would have been a sheet of white polyester. I don't think there is such a thing as a PE "cored" paper--in that it's a paper core inside 2 layers of polyethylene. At any rate, the emulsion is on top of all this mess--even if it's the TO that causes problems and worries---the emulsion can still fade, stain and get attacked by pollutants.
Doesn't surprise me that the Ilford paper costs more than regular paper though--we use some Mylar D enclosures and they cost about 3 times as much as polypropylene, and even more than polyethylene--but here again, it comes down to the environment--at a certain point, even these "safe"materials can cause damage--you see that in sleeves & enclosures alot. It all comes down to the temp & rh. I went to an IPI workshop once, and it was a great weeklong learning experience--so packed with info, you just couldn't take it all in. One thing they kept saying was to tone everything. Film, paper, etc. Tone everything in selenium or sulfide toners. The other was that when it came to film, there were 2 priorities--the "needs of the base" and the "needs of the emulsion". The base was controlled by the environment--and if that failed, it wouldn't matter much about the emulsion at that point. I know there are inherent differences in all these materials, and it might seem odd to talk of film & prints lumped together, but silver is silver...
my opinions only, KT