So for all of those who are obsessed with learning to paint form with accuracy in light and shadow, here is a really handy chart that Greg Mortenson made for my painting class. I also like how he made the tones broken down into nine values. It looks easy when you see it broken down on a simple sphere, but once you try and apply it to a face, not so easy!
Forgive my palette done on palette paper today, but this is a simple illustration of painting in "strings". Greg showed me how to mix a nice warm out of Gamblin's Asphaltum and Ivory Black, then mix it with white gradually till you get this nice gradient of values. You can also mix this with just Ivory Black and White, or any of you mother tones you want to make a large pile of. Then, once you have you basic values established, you can mix the two in the middle to get warmer cools, or add chroma on the outside for more variations.