after two days, the mold is peeled away and the cast allowed to cure for seven days. Any plant toxins in the cement are neutralized by filling the trough with water and adding about 2.5 g of dissoloved potassium premanganate. After two to three hours, the solution is discarded and the trough is rinsed out. Drainage holes are drilled into the trough. Troughs are allowed to cure for another two or three days. See MacPhail(1990) for details on reinforcing thin (less than 5 cm thick) troughs with hardware cloth, creating textural refinements, using other materials, and readying the trough for final planting.