Most of us are familiar with Plasticine and Aloplast which is very similar. Other commercially-produced materials are Play Doh and some new ones which will set rock hard without being fired. These are slightly different in texture from clay or dough and from each other. Their main drawback is expense so that children are rarely able to have a large quantity at a time. They all need to be kept in good condition. Plasticine needs to be warmed slightly in cold weather. Play Doh will dry out and cannot be restored to its original texture. It may be that their special properties are useful for older children but for the pre-school age range the usual provision of clay or dough seems adequate with perhaps a very occasional change to a Plasticine-like material.