This is a sgraffito- white lime plaster is scratched back to reveal the dark lime plaster below. It is a classical technique used in Classical times and since revived. It was popular in the Art Nouveau era and used in architecture as well as pottery. This image is of the whitebeam tree seen from my window. The technique allows for no correction, so the marks are very direct and spontaneous. I have painted white pigment, in buon fresco technique, on some of the leaves.