The good,old,fungus on Ektachrome question,revisited
Case in point : a friend with a quantity of unmounted slides,70's era :obvious fungal damage most visible on the surface in reflected light,but does not appear to have damaged the image itself.
I cautioned him against using anything water-based,but that's the limit of my expertise.
A product called PEC has been suggested.I also have on hand Edwal Film Cleaner,and some high purity isopropanyl alcohol.
Checked the threads on this before posting- but any helpful update would be welcome.
The film was probably processed in Australia : does anyone know if a protective lacquer was used at that time ?
You might try a few of the products mentioned, but do it on a small piece of film, and preferably an image that is not very good in case you have bad results. I made the mistake of trying PEC on a Kodachrome slide that had fungus. Nearly ruined it.
Avoid alcohol. Even "laboratory grade" alcohol will have water in it. Even if you could get "100% alcohol," the moment you opened the bottle, it would start absorbing water right out of the air.
Alcohol can be used sparingly and carefully but I would not use it on archival film or film with sentimental value.
The "correct" thing to use would be trichloroethane or carbon tetrachloride... if you can find it.
I have heard that PEC-12 should not be used on some kinds of film but I don't know the particulars. I know that its main ingredient is methanol. Again, you have the water absorption issue because methanol is hygroscopic but I don't know about any other substances that can be used for cleaning film.
Regardless of the substance used to clean film, you have to be really careful. Use a soft, lint-free swab or pad. Apply the cleaner, sparingly, to the swab then carefully dab or blot the film with a minimum of wiping. Work in small areas. Don't move to another area until you have the first area clean and avoid smearing dirt from one spot to the next.
That's, pretty much, all I know. Common sense, really.
P.S. - You might want to consider scanning the film and digitally removing the dirt or fungus spots. Most film scanners have infrared dirt removal features that work pretty well if you do it right. The rest can be cleaned up with Photoshop or GIMP.