Quote Originally Posted by DKT
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 emulsion is coated on top of the plastic.
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.