Kodak used to make a whole line of chlorobromide papers using the trade name
"Opal." Unfortunately, these were very slow papers that didn't fit in with
the rapid processing required these days. "Opaline Parchment" was a thin
weight paper in this series, if I recall correctly, with a semi-translucent
base so it could be put in a light box for back-lighting, if desired.
Sil Horwitz, FPSA
Technical Editor, PSA Journal
silh@iag.net