Van Aken Modeling Clay - Quality, economically priced modeling clay. It never hardens, remains pliable and plastic and can be used time and time again. It is self-adhering, non-toxic and is used by sculptors, model makers, clay animators and artists of all ages. Streaking may occasionally occur during the color formulation process, and can be dissolved as the clay is worked by hand. Certified non-toxic by the Art & Craft Materials Institute.