How do you make sgraffito?

To create sgraffito, first draw your picture or pattern in pencil or oil pastel. Then cover the whole page in black oil pastel. Scratch at the black pastel with a lancet or other sharp tool to reveal the picture beneath. Another tool that may come in useful for removing the black pastel is the 'wrong end' of a paintbrush. This is the method I usually use and it is very effective.