Sand resist in watercolor?
Several years ago I learned how to use sand to illustrate a weathered stucco wall in the South of France. It involved wetting the paper (just water, or a light wash?), sprinkling sand (let it dry, or continue wet?) and dropping in other colors. When dry and the sand was brushed off the effect was very like the mottled stucco wall. I've since forgotten the exact method-- does anyone know?
edit: Thanks, Jay, but that was not what I meant. I am doing a watercolor from a photo I took of a flower-covered balcony in Venice. The wall of the building is very old and mottled, and this is the effect I am trying to remember how to reproduce.