Cleaning Kodachrome Film
This was published by Kodak in "Kodak Data Book On Slides"
(third edition 1947 pg. 23-23, reproduced by scan of the original publication.)
Kodachrome before 1955 usually has a protective laquer on the emulsion. Often the laquer has cleaning marks or embedded matter that must be removed for scanning. The emulsion on early Kodachrome is extremely fragile. Aggressive cleaning treatment will irrepairably ruin the original. It is recommended that conservators practice on surrogate samples before treating an important image. There are several types of Kodachrome emulsions and laquers, requiring different treatments. It is always a good idea to test a sample slide from the same lot when considering intervention techniques.