[Pram Maven]

Fun stuff.

I wonder what adding beeswax would do it? Or even paraffin. Both plasticine and polymer clays have a mineral oil base, which for you chemists out there is made of short chain carbon molecules. (microcrystalline wax has long chains, making it more sticky and flexible).
Paraffin would make the clay more brittle, but maybe in really small amounts it would improve it a little.