>proper material. The other consideration is that there may be a UV
>inhibiter in the transparency material that would inhibit doing cyanotypes.
>That last thought is pure conjecture on my part.
Mylar is completely opaque to UV, so it would do more than inhibit, it
would prevent exposure! It's interesting to put a piece of Mylar (polyester
film) in the path of a UV lamp shining on paper or cloth that has UV
brighteners in it; the area covered by the Mylar is completely black.
The transparency films for laser (including copying machines) and dye-sub
printers must be heat-resistant, which Mylar is, so I would suspect it (or
one of its derivatives) is the base material. Mylar is also dimensionally
stable.
As another point: the "Estar" base films use polyester film; these could
also be a problem with processes requiring UV exposure. I haven't done any
testing in this area, but it's a good one to place in my backlog. Has
anyone experimented in this field? If so, let me know, as it would help in
providing a starting point.
Sil Horwitz, FPSA
Technical Editor, PSA Journal
silh@iag.net