I did a search for you and found this:
The best clay for your Claymation
From the nature of the different types of clay above, the non-hardening plasticine or plastalina clay is the main clay used in stop animation. These are manufactured in different colors and stay soft and moldable even for a long period of time being exposed to air or room temperatures. But this doesn’t mean that the other clay types are not important. The hardening clays are also needed to create your Claymation characters or parts which are not movable. The hardened clay or figure will also serve as the internal support or frame of the soft plasticine clay. To simply explain, your clay animation characters will eventually have movable and immovable plays. The hard immovable parts are where the other types of clay such as polymer are best suited.
They key things to remember when choosing your in summary are :
OIL BASED
NON HARDENING
SELECTION OF COLORS
FLEXIBLE
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Best Clay to use for Claymation Animation - iKITMovie Stop Motion
Newplast is a non drying, re-useable claymation modelling oil based clay. It is available in layered 500g bars. It is easily pliable to make a variety of clay models but is firm enough to retain its shape well for some time.
Aardman have used Newplast which is made in the UK and they have also use Van Aken (which is made in the US ). However they now use their own special proprietary mix called “Aardmix”. No one outside of Aardman is 100% sure what goes in to making it but I would suspect it is largely Newplast plus one or two extra oils to make it even more pliable.
If you are new to stop motion animation and in particular claymation then we advise you on what is the best clay to use for claymation animation
www.ikitmovie.com
