Yes, that's what I figured. When the cups came out brittle and shattered I had no idea which ingredients/ratio of ingredients/lack of ingredients had caused it.
I've been learning VERY slowly from trawling digitalfire materials and google, but it's like troubleshooting into space. Hence a good textbook or two would help to focus me on what I need to know. If only I could afford to go back to school and do a formal ceramics degree!
A book I have here is: "Notes for potters in Australia vol.1. Raw materials and clay bodies"..author Ivan McMeekin May be able to get it a t a library.