Sand Sculpture This is recommended for older children, as the mixture may be too rough for little fingers to mold. 2 cups clean sand 1 cup cornstarch 1 cup water Slowly heat the mixture in a heavy pot, stirring occasionally, until thick (about 30 minutes). Turn the thickened mixture out onto a cookie sheet or shallow cardboard box. Work with it immediately. Allow finished pieces to dry for 24 hours or set them in a cool oven (200 degrees) for 4 hours. Turn off oven, open door, and let pieces finish drying for another 4 hours. Finish by sanding rough edges with an emery board. Add fancy details such as flags, trims, bushes, etc. with white glue.