“Sgraffito” comes from the Italian word meaning “to scratch.” And it fairly well sums up the process.
First you need something to scratch on.
Then you paint on some nice thick coats of underglaze, while its leather hard.
Then you scratch out a pattern. I have endless amounts of doodles to look at if I’m ever having trouble deciding exactly what I want to do. Then you bisque your pieces so the pattern is fired on.
Finally, add a layer of clear glaze and fire again and voila!