Ooooh I did not know that about Barry .
Not a surprise though with his wonderfully resonant tones. Sadly I only met him a handful of times.
One of many folk taken too early .
A plastic moulding compound called "Fastcast" can be swirled around a mould.
It sets very fast , but while still liquid the effect is somewhat similar to swirling warm wax around a candle mould .
Ive used fastcast only a couple of times for props. ( candle making is a distant childhood memory now - great fun though )
Fastcast is very brittle and cracks very easily.
However it was some years ago since I used it. I use resins almost never now, but I do know from friends who make props that new plastics and resins seem to come out almost monthly , and that keeping up is hard.
What was only available at very high cost to factories and big production houses in bulk , is now available cheaply in small quantities.
So there is probably a resin that works in the way you describe.
Like Les I would be interested to actually handle one of the resulting puppets to see if they are strong and resilient .
I have just replenished my supply of regular fibreglass resin and clear casting resin as I need to mould up some matching sets of crocodile eyes.
It has been years since I have made any puppet eyes for 'muppety' type puppets, and have exhausted my stock
So when I have made the "croc" eyes I will use up the rest of the tin of resin making other puppet eyes.
The resin only lasts a few months in the tin once you have opened it ...so I might as well use it up creatively ( the croc eyes will be expensive items otherwise )

A pic of eyes made years ago ..before the final clear resin layer
Best Richard