Unfortunately, the history of industrial products seems to be generally incomplete and murky. For some reason, we don't think it is important. We just discard the old and go on. The history of Kodak films is like this. Since the early Kodak color products were highly proprietary (Kodak controlled sales closely and did all processing in house up until after WWII), about the only way to trace them is through advertisements. Both negative and positive Kodak color films date from the early 1930s. The history of Kodachrome is fairly well known, although its maturation and the various changes the film manufacturing and processing went through would be hard to determine. As I recall, Kodacolor started as a very bad two color sandwich roll film product about the same time as Kodachrome. It rapidly improved to a thee color film. It gained its masking later, I think (but am not sure) sometime near the end of WWII. Ektachrome came about the same time and Ektacolor (a professional version of Kodacolor in sheet film sizes and allowing user processing) a few years after that. Once again, these products changed a lot over time, and it would be very difficult to determine just when and how. With Ektachrome and Ektacolor, Kodak did publish formulas, and researching old technical publications along with contemporary advertisements and reviews might provide some clues. Sorry I don't have better information. I would like to know more, too.
