Self-hardening clay is suitable for all hand methods of modeling. Moist form is ready to use. When dry, modeled objects are hard and durable without any firing and accept any medium. Coat dry pieces with varnish for extra strength. Marblex is prepared in moist form, ready to use. 25 lb. package of gray clay. Gluten-free. AP Seal, non-toxic. Does not qualify for free shipping.