The ground? Well, it's whatever my sitter shows up with. In this case it was some kind of stretched, medium weave canvas. How's that for specifics?
I do realize how much I have come to love my smooth, rigid New Traditions' surfaces, as the paint behaves so differently on texture, and my not-very-delicate touch threatens to poke holes in the stretched canvas.
However, as I write, I realize what a great excuse I might have for bad demos! I'll try it out and let you know how it works.