A nonhardening substance used for modeling sculptures ? Roma Plastelinafor sketches, models for casting, and by students. It is plastic (in the sense of being workable). It cannot be used for permanent work (unlike ceramic water-based clays, it is never fired or glazed). colored modeling clayAlthough it becomes less useful as its oil either dries or is absorbed from it (making it brittle) or as it picks up impurities, but it can be reused for many years if kept relatively clean. Even new it can vary greatly in quality. Most common varieties are made of clay mixed with petroleum greases, oils (typically linseed oil), turpentine, sulfur dioxide, and pigments. It softens as it is modeled by the hands (because of their warmth), pieces joined to each other by pressing them together and blending with fingertips. Equipment that might be used with modeling clay include modeling tools and armatures. Molds can be made from modeling clay. There are numerous commercially produced types, including the brand named Plasticine. It is sometimes called model clay.clay menagerieSome of the additives in oil-based clays, such as turpentine and MEDICAL ALERT!preservatives, might cause skin irritation or allergies, and sulfur dioxide might cause some respiratory problems in certain asthmatics. The amounts present are usually small. Use gloves or apply a barrier cream to hands if skin irritation results from using modeling clays. Clean hands well after contact by washing them with soap and water.Also see Material Safety Data Sheet (MSDS) and polymer or PVC clay.