One of the things I do with the robot draings is sketch on vellum. I tear up tracing paper by drawing too hard and erasing too hard, so I don't like it, but vellum is much thicker. The nice thing is that I can make a drawing, tweak it a little, then fold over the paper and trace to get a cleaner version, or fold the paper to get one side to match up with the other. I also like that I know from the start that when I am drawing on vellum it is just a preparatory drawing. When I draw on paper I get trapped into thinking whatever I draw has to be perfect and finished, even if it is just intended as a plan for a painting. Then I get stuck and don't finish. But with the vellum I know it's not meant to be a finished piece, so I loosen up a little. Anyway, here's a scan of some sketches I did one day a few weeks ago.