Cornstarch Play Clay 1 cup salt 1/3 cup water 1/2 cup cornstarch 1/4 cup cold water Food coloring In a medium-size saucepan, mix salt and 1/3 cup water over medium heat, stirring occasionally (about 3 to 4 minutes.) Remove from head and add cornstarch and 1/4 cup cold water. The mixture will resemble mashed potatoes. Stir until mixture thickens; cool, then knead. If it's too sticky, add a little more cornstarch. Store in sealed container with piece of damp sponge up to two weeks.