I have only scratched the surface for how the family of angles plays into photographing various materials. If you care about lighting, please do yourself a favor and get a copy of the book “Light: Science and Magic: An Introduction to Photographic Lighting” by Fil Hunter and Paul Fuqua. It covers this subject and much more, in-depth and in a way that makes it interesting and easy. Google books has an excerpt here.
The next post covers a little product photography from a recent shoot. Come on back and I'll show how I approached lighting a larger than tabletop object.