This week, while studying Michelangelo, we revisited fresco painting. We did this last year when Giotto came to visit us. But this time the kids traced a picture onto tracing paper, and after we mixed the plaster of Paris with water and let it set a few minutes, we laid the tracing paper on top of the plaster and used a pin to poke the image through to the surface leaving a line of pin holes. In Michelangelo's time, they did something similar using chalk to leave an outline on the wall where they would paint.
So here Gianna is poking her image: