Older films (like Efke / CHS 25, RIP) came on PET base, so there's a notice on their web site:

"CHS 35mm and 120 Films are beeing coated on clear PET. Therefore the films are sensitive to light piping. We sell all 35mm and 120 films in black plastic containers. Please load your camera only in subdued light and put the films back in their black containers as soon as possible."

I got FP4 and HP5 in a foil: http://www.flickr.com/photos/jernej_...in/photostream