It is a bit more complex, with various formulations based on diacetate, proprionate, formiate, butyriate and triacetate competing for almost fifty years (all of them plagued with occasionally turning into stinking goo without any obvious reason), until a highly stabilized triacetate was introduced in 1958. Which is still in use today, except for special applications requiring high dimensional stability, where polyester bases directly succeeded nitro film, the whole acetate group having issues in that domain.
Bookmarks