Tap washed pottery shards in pans of water, scrubbing them with a toothbrush. The more delicate pieces he cleaned with a small paintbrush, fine-bristled.Kathryn and a male student worked a device called a rocking screen. The young man troweled dirt from a tall pile into a plastic bleach bottle with the upper section cut off. He spread this dirt onto a horizontal screen equipped with handles and held in position at elbow height by a bracketed wooden framework. Kathryn gripped the handles and rocked the dirt through the fine mesh, one hour, two hours, three hours.I sat in the shade, watching.