CinePost recently had a client with some film that suffered from mold/fungus. It shows up as spidery snowflakes/spots and is very distracting. The results are never guaranteed, but we’ve developed a method of soaking the film in a cleaning agent for several days, and then hand cleaning after to remove the mold/fungus. In this case we were able to remove the mold almost entirely! The untreated film is on the left with the cleaned up film on the right.
Mold on Super 8mm Film shown Side by Side: Removed on Right by CinePost from CinePost on Vimeo.