As one who has struggled with categories in the past on other forums, it's important to have categories which are OBVIOUS - or people will choose incorrectly.(posted 8616 days ago)I'm a little unclear on the distinction between "processing film" and "developers" for example. Subtle differences in categories often cause confusion.
I presume "chemistry" is for fixers, stop baths etc? (but not developers or intensifiers?).
Note that you can't change category names once you create them, nor can you transfer posts in bulk between categories (you have to do it one post at a time), so it's worthwile making sure you get it right to start with, or you'll have to do a lot of work to change it!
Good luck.