Drywall Ancient Greek Columns Project. JR HI MIddle School. Every year our 7th graders learn about Ancient Greece. We use water to rub off the brown layer of cardboard on a 6"x8" piece of drywall. Because we use water the clay inside becomes a little damp which makes it easier to carve. We use a pencil to draw out our design then clay tools to do the carving. Tempera paint in "antique" colors and natural sponges are used to add the color. This takes about 45 to 60 minutes to complete.