On 10/8/2009 2:36 PM laran spake thus:

What is ruby lith? I need to find a source and don't even know what it
is (using as my red filter for my enlarger - possibly)

Rubylith (one word) was (and still is, if it's still available) a trade
name for transparent red masking film used in the graphic arts (notably
in the making up of flats for offset printing, known as "stripping") as
a photo-opaque film (orthochromatic photosensitive materials like offset
printing plates are insensitive to red light). Cut-out areas in printing
flat could be covered with Rubylith to eliminate printing marks on the
plate caused by light exposure.

From the Madison Avenue-ese "ruby" (meaning "red") + "lith" (as in
offset lithography).


--
Found--the gene that causes belief in genetic determinism