I know this is late. Sorry, guys.
Now that I've laid down some guidelines on Transmutation effects, let's see them in action. One of the many Transmutations that we see Mrs. Yoop do in The Tin Woodman of Oz is turning the Tin Woodman himself into a Tin Owl. If this were nearly any other character, this would be a Transformation using those rules. But since the Tin Woodman is made of tin rather than flesh and bone, this spell is considered a Transmutation.
This involves a change to both Form (he now looks like an owl) and Function (he can actually fly like an owl, too), so 2 points of Power there. He also takes a reduction in Size, but his Substance (tin) remains the same throughout. So altogether, it's a Power 3 effect.
Power: Transmutation, Tin Woodman to Tin Owl (3)
Scope: Person/Object (1)
Ritual: Simple (-1)
Duration: Permanent (2)
Effect Power: 5
A pretty powerful spell, really. Mrs. Yoop must have some Oz Points hiding somewhere in order to pull that one off.