Newplast™ and Scola Colourclay are a non-drying, non-setting modelling material. They are virtually identical to plasticine, and can be re-used many times. The material is sufficiently pliable to make a wide variety of models, but is firm enough to retain its shape indefinitely. It is the material specified by most animators as being the only fit-for-purpose plasticine available. Similarly, it is used extensively in industry, for a wide variety of applications ranging from construction to medical device manufacture.
This material is also suited for use in mould & plug creation / sealing / filling.