contact printing alt processs under acrylic/perspex/plexiglass

If you are doing alt-process contact prints that need UV to expose image, be
aware that acrylic sheet filters more UV than glass.

I believe Perspex is acrylic and not polycarbonate as is Lexan. I do not
know UV filtering properties of polycarbonate.

Regular glass (picture framing Tru- Vue brand) filters about 44% of the UV
spectrum shorter than 380 nm.

UV filtering acrylic (like Cyro OP-3 or Ato-Haas UF-3, UF-4 or UF-5) filters
98% of the UV shorter than 400 nm. It takes a little of the blue/violet out
of the visual light spectrum.

'Ordinary' acrylic sheet doesn't have a UV filtering spec...you have to
inquire...it's between 70 and 80% for Ato-Haas' product, and presumably
similar for others. The filtering spectrum is shifted as well and not
characterized.

I was told that both regular glass and acrylic will filter the very short
wavelengths (below about 200 nm if I remember right).

Strictly textbook here - I haven't tried either yet, but I would expect
less UV will get thru acrylic/Perspex sheet.

Murray
Received on Sun Sep 1 20:17:31 2002