I do not paint on paper or canvas, I paint on, or rather under glass or any clear surface - perspex or acetate are just as good.
The surface I apply the paint to will become the reverse of the painting. The marks I apply first will make up the foreground and detail of the finished image. It is, literally painting in reverse. As I apply paint I need to regularly turn over the plate to see how the image is progressing. Once I apply paint onto the plate I can no longer alter how it will look in the finished piece since painting over a mistake is not possible, any mistakes would need to be removed and repainted onto the clear surface.
As a process it is unpredictable, changes cannot be made once the marks have been applied. Finishing touches need to be applied first. As the 'canvas' is actually a piece of transparent glass or perspex, the finished image has a luminosity to it, light reflects from the smooth transparent surface as opposed to being absorbed into the texture of the paint.
The Horse (framed)
Red and Blue