 Main character heads were initially sculpted in either <unk> or clay . Once the general aspect had been finalised , this served as the template for a <unk> rubber mould . This was coated with <unk> ( fibreglass mixed with resin ) and enhanced with <unk> , a <unk> @-@ like substance , to <unk> <unk> . The <unk> shell was then fitted with a solenoid , leather mouth parts and plastic eyes , as well as <unk> teeth – a first for a Supermarionation production . <unk> known as " <unk> " , which had plastic heads , portrayed the supporting characters . These <unk> started their working lives with only a mouth and eyes ; their faces were <unk> from one episode to the next . Particularly striking revamp moulds were retained and , as their numbers increased , photographed to compile an internal casting <unk> . 
