Moulds and Casts
Heads were initially carved in wood or clay by hand, by people such as Percy Mortimer, Gill Leaper and Peter Carter-Page.
Moulds were taken using plaster of paris (in the early days these were used to make solid heads which were heavy) and cast usually using a material called Revertex. The heads were 10% bigger at this point to allow for shrinkage later in the process.
These heads were then sent off to the foundry and metal moulds (mostly aluminium but some in brass) were cast.
The moulds then went back to the factory where people like Percy would finely finish the surfaces to ensure no imperfections were left in the mould, as these would would be visible in the final cast.
Pumice (reportedly from Mount Vesuvius in Italy) was mixed with Gelatin to make a pourable mix, the consistency of batter.
This was was kept in a giant vat heated by a tank full of hot water at a consistent temperature.
The pouring moulds were held together, front and back, with strong elastic bands. Liking to re-cycle, Bob would use bands made from old car inner tubes. Today, most tyres are tubeless but back in the 60's and 70's inner tubes were more common place, so easily found.
The mould was placed on a large bed of ice to cool. It was then taken to the tank and filled through a non-clogging sugar tap with the hot liquid mix. The mould was rotated by hand to release any air bubbles and evenly coat the inside. This was a skilled job as too little would result in gaps or weaknesses in the cast leaving it brittle. Ron Louth, head of the pouring room was an expert at this and trained most the staff on how to create the perfect cast.
Any excess was then poured back into the vat and the mould was up-ended and placed on a tray above the vat to allow the mould to drip (you can see this in the picture of Ron from Pelpup news 26)
The mould was again placed on a bed of ice for around 20 minutes until the cast became like set jelly. People working in the area would have a run of up to 40 pieces and would know when each were ready to be removed from the mould. They would carefully prize it open and remove the jellied cast, returning the mould to the ice bed ready to be used again. The cast would be carefully trimmed of any raised seams or excess protrusions and these would be put in a bowl to go back into the vat to melt back down. Any cast that didn't look right could also be put back in the vat, ensuring little or no wastage!
The next stage was to place the cast onto the drying rack. This was a wooden frame with rows of dowels covered in a cloth mesh. The cloth mesh would sag in half moon rows between the dowels creating a hammock effect, and therefore allowing maximum air flow and even support with minimum pressure during drying. This rack was placed in a giant cupboard with sliding doors with a huge fan at one end. This drying 'tunnel' would help the casts to dry evenly, but even then it could take upto 24 hours.
Once the moulds were set they would be categorised on trays and placed in the racks of tea chests (you can see the numbered tea chest in behind Ron in the above picture). The painters would then come each morning and take what they needed for the day.
Over time moulds would need re-fitting. Engineers Blue would be painted on one side then the moulds held together to see which sides needed to be filed to once again create a seamless fit.
Bimbo Mould and Cast (Pelpup News 26)
Heads & feet on drying rack (Pelpup News 26)
In this photo (Pelpup News 26) Rosita and Mrs Hands are making pressings of puppets feet. This process produces a solid cast useful for hands, feet and Skeletons, all of which have to be heavy.
The materials used were similar to the ones described above, but were not so fine. They used rabbit glue not Gelatine and ordinary white mineral powder as opposed to expensive pumice powder. The warm mixture is made into a dough and formed into long sausage shapes, which you can see being placed in a flat sided mould. Then the top half of the mould would be put on top and placed under a mechanical press with a pressure of 1000 lbs per square inch.
In a similar way to the pouring moulds, it was then returned to the ice bed to cool. After a while the moulds were opened and the contents placed on drying racks. These could take upto ten days to dry.
Rosita and Mrs Hands pressing feet. (Pelpup News 26).
Shirley and Ron Louth pressing hands (Pelpup News 11).
A Macboozle Hand Press from the factory.