Stonex Self-Hardening Clay. This self-hardening white clay is prepared in moist form and ready to use. When completely dry finished pieces are hard and durable. Water can be used when clay begins to harden while working. When pieces are dry clay can be decorated with Rub n Buff, school paints, temperas, acrylics or liquid crayons. Air dry only. This package contains 5lb/2.27kg of white clay. Clay conforms to ASTM D4236. Made in USA.