Ouch Mark, I hadn't thought of dry mount tissues as a source of contamination. So what do you use instead to hold the print flat?
I have evolved to an adhesive-free style of mounting/framing for my personal work. Would be easier to show in a video sometime, but I'll try to provide some insight with a modest verbal description here.
First I prefer the beauty of wood frame for my work, so I use wood frames, the caveat being to seal the rabbets with frame sealing tape (e.g. Lineco frame sealing tape). This tape looks like a white paper tape, but it has an internal aluminum foil carrier, so it isolates both the wood and even its own adhesive from the print, mount board and overmatte when used. It eliminates any concern about off gassing from the wood discoloring the edges of the print.
Second, I print with wide margins or trim borderless when I want a borderless look. For my borderless prints, I print on a matte fine art paper such as Moab Entrada natural 300gsm. Framers all advise that placing a photograph in direct contact with glazing is bad practice, but they learned this from experience with silver gelatin prints. Gelatin is gelatin which means at moderately high humidity (70%RH which is a very real world result in many regions of the world) it reverts to gel state. then as humidity drops it blocks and sticks to the glass. However, a fine art Matte paper like Moab Entrada does not have a gelatin binder and the microporous silica in its binder acts as an anti-blocking layer to prevent the well known "ferrotyping" issue with traditional photos. Hence, placing the matte fine art media in direct contact with the glazing is a totally safe practice in my situation, and in fact it gives the print nearly the same visual "pop" that folks get with other face mounted acrylic print methods yet retains total reversibility. If the acrylic scratches, simply disassemble the piece, remove the print and replace the acrylic.
Third, I add a 2 ply conservation matte/mound board behind the print to serve as additional moisture buffering material in the framed print's microclimate environment. Then I lay in an oversized 1/16 inch PE foam liner sheet into the frame followed by a conservation grade foam board and finish off with framing points. Then the excess PE foam is easily trimmed with a utility knife (cuts like butter). The PE foam is doing a couple of things. It is first and foremost a vapor barrier, not a perfect one, but good enough to stabilize the microclimate in the frame to mitigate daily/weekly/monthly RH swings which when severe enough contribute to cockling of some artwork on paper over time. It is also a dust jacket but hidden underneath the foam core board rather than placed on the back of the frame (I can't tell you how many torn dust jackets on the back of frames I've seen over the years, my approach avoids that problem). Lastly it cushions the print and Matt board assembly to even out any pressure points in the package and thus helps to ensure the print expands and contracts uniformly over long periods of seasonal RH cycles.
For my prints where I want an overmatte, I simply print a wide margin border (e.g., 2.5, 3, 4 or more inches of margin around the image) such that the final print size matches the overmatte, mount board, and frame's inner dimensions. This eliminates the time-consuming practice of T-hinging, corner mounting, etc and gets rid of any adhesives inside the framed print microclimate. One just inserts the glazing into the frame, then the overmatte when used, then the print, then the 2 or 4 ply mount board, then drop in the PE foam layer, finally the foam core backer board, and finish off with framing points. I concede my technique of wide margins lends itself to 24 and 44 inch printers better than the smaller prosumer desktop models, but the time and labor savings are tremendous, i.e., worth it to consider stepping up to a 24 inch printer over a 17 inch desktop model. I often print the image with a fine stroke line which shows where to cut, and then the image, and the overmatte, mounting, and frame components all self align..not tedious measurements to get image and overmatte looking perfectly centered.
I've used this approach to framing my work for several years, and so far so good. I also routinely print at up to 32x40, so I can confirm my method works well up to that size. I don't have any need to go bigger with my personal work, but I'd guess the technique could be adapted to larger pieces, perhaps going to a stiffer backing board, slightly thicker PE foam, and a thicker acrylic glazing sheet for larger pieces.
I hope that describes how I avoid adhesive mounting techniques entirely when printing and framing fine art inkjet papers.
cheers,
Mark
http://www.aardenburg-imaging.com