A theorem painting uses a set of stencils, or theorems, to complete each design. It was an art form that was taught at young ladies' finishing schools from the early to the mid-19th century as part of their training in home arts. Theorems can be painting on white cotton velvet (aged with a bath of coffee or tea) or on heavy paper, using either oils or water colors.
I use mostly cotton velvet and occasionally paper, but I always use oil paints. Details are added with a fine brush once the stencils are complete. Frames are custom made by my husband, and then false-grained or milk-painted in appropriate colors by me. When I can buy an antique frame at a good price, I'll use that, too.