Cadmium elimination effect on paper storage life

[Sal Santamaura]

There's been much posting here and elsewhere about the elimination of cadmium from fiber-based printing papers. Discussions usually relate to possible effects on image quality. I'd appreciate anyone with detailed information on the chemistry involved sharing what they know about how unexposed paper storage life might be affected.

This question is posted with an eye toward acquiring a large quantity of Azo. Although it is an extremely slow paper, and has a reputation for lasting virtually forever without fogging (suffering only a slight reduction in contrast after many, many years), I'm concerned that recent changes might have diminished its long-term keeping qualities.

Thanks in advance for your inputs.

[N Dhananjay]

I do not know the exact role of cadmium - I think it was used to tweak the characteristic curve, but hopefully someone else will know more. As far as the longevity of Azo is concerned, I will hazard a guess that it is still excellent. Clearly, we know old Azo could last decades (since we have decades old Azo lying around to test and prove that notion). We obviously cannot say that about the new stuff since it is just being manufactured - the only data point I can provide is my own, 4 years and going. However, I think the reason for Azo's longevity is primarily the fact that it is chloride emulsion and is therefore, very slow. This makes it much less suceptible to fogging and degradation. Its probably a good idea to cold store it etc but I would not expect a significant (order of magnitude kinds of stuff) reduction in longevity. Hopefully others will chime in with more info. Cheers, DJ

[Ron Mowrey]

Fyi guys, EK launched a comprehensive program to eliminate Cadmium and Mercury in all photographic products (paper and film) that contained these elements. In addition, Lead and a number of other noxious items were either eliminated or reduced.

I don't feel free to discuss the purpose served by these chemicals, but suffice it to say that todays products all keep far better and have better and more reproducable curve shapes.

In fact, most EK color and B&W papers can be kept at room temperature for quite some time without significant change taking place. I have kept color paper on the shelf for over a year with no real change.

Now, I limit my comments to RC based paper products and film. Traditional paper based products keep more poorly than RC based or film products in my observation. I don't know the reason, but I suspect that the paper is capable of absorbing chemistry from the emulsion which the RC and film supports cannot.

Hope this helps.

[paulr]

"Traditional paper based products keep more poorly than RC based or film products in my observation. I don't know the reason, but I suspect that the paper is capable of absorbing chemistry from the emulsion which the RC and film supports cannot."

Hmmmmm.
Is this conjecture? I seem to remember tests (including ones by Wilhelm research) finding just the opposite.