Pewter figurines are cast from hot metal using rubber moulds in a centrifugal casting machine. The rubber moulds are made by placing a 12" rubber sheet in the frame and laying out the master patterns around the mould and placing another 12" rubber sheet on top. The frame is then covered with a tight-fitting aluminium disc and placed in the vulcaniser (below Left).

Pewter figurines are cast from hot metal using rubber moulds in a centrifugal casting machine.

Pouring Metal

The vulcaniser is a piece of equipment designed to heat and pressurise the the mould frame to cure rubber in the mould making process. The Vulcaniser consists of two thermostatically controlled platens and a 20 tonne hydraulic ram for closing the two platens onto the mould.

The control panel consists of two thermostatic controls and a timer.

Each platen has it's own thermostat and these are set to 165º C.

The timer is adjustable according to the thickness and size of the mould to be made.

The mould frame should be powered with talcum powder to prevent the rubber from sticking to the mould frame.

Two disks of rubber about 12mm in thickness are then powdered with Talcum Powder to prevent the two disks from sticking together when the rubber is vulcanised. It will also allow for the removal of the master patterns when the mould is made.

One rubber disk has to have a hole to allow the pewter to be poured into the finished mould.

The centre is marked out.

The raw rubber is cut with sharp knives.

The rubber is very pliable before being cured and may be easily cut.

The centre is removed and the aluminium plug (right in picture) will be inserted in the hole.

The rubber is then coated with talcum powder again.

Care should be taken to ensure that the rubber is well coated with talcum powder.

The mould frame has been placed in the vulcaniser for an hour to be pre-heated to about 160º C. All the aluminium filler plates are also heated.

The mould frame is removed from the vulcaniser using insulated gloves.

The filler plates are also coated with talcum powder. Whilst the bottom rubber disk is being warmed.

The mould frame is again powdered ready for the first rubber disk to be inserted

The warm rubber disk is pressed into the mould frame by hand.

The rubber is again powdered.

The centre plug is powdered and inserted in to the hole.

The figurines are then placed on the rubber towards the outer edge of the mould and about 18 mm in from the mould frame perimeter.

even spacing is essential to ensure a balanced mould when it is spun in the casting machine.

The rubber in the mould frame will be the top half of the mould and whilst the figurines are place on this rubber the other rubber is being warmed.

Once the figurines are in place locaters are placed between each of the figurines. This is necessary to ensure that the top and bottom parts of the mould always fit together.

The locators are now in place with plenty of space between the outer edge of the mould.

The second rubber disk is then pressed carefully into place so as not to disturb the placement of the master patterns and powdered.

A sheet of release paper is placed over the top of the mould to ensure that the rubber does not stick to the filler sheets.

About 8 - 10 sheets of newspaper are then placed over the top of the mould frame to ensure a tight fit which will not allow the rubber to seep out from the frame when heated and under great pressure.

An aluminium plate is the carefully pushed into the frame so as not to disturb the placement of the master patterns.

Once the first aluminium plate is in place, the excess newspaper is cut away using the outer edge of the mould frame as a guide.

A second filler plate is in place and the paper is cut away.

The second filler plate is carefully pushed into the frame.

Any excess paper is then cut away.

The vulcaniser is still at 160º C and the frame is then placed in between the vulcaniser platens.

The frame is always placed in the centre of the platens to ensure that an even pressure is exerted to ensure that the mould will be parallel.

The bottom platen is then slowly jacked up to full pressure to ensure that the rubber is squeezed around the figurines and into all the undercuts.

The vulcaniser is at 160º C and the frame starts to heat quickly.

The frame is now under full pressure and the timer is set for two hours.

After two hours, the pressure is released on the platens and the mould frame is removed from the vulcaniser.

The melting pot is used to melt bars of pewter. It holds over 60 Kgs. of metal. The temperature of the metal is measured with a thermo couple and a thermostat controls the metal temperature within a few degrees.

Pewter is cast at between 290º C and 320º C depending on the bulk of the pieces being cast. The ladel will hold about 2 kgs of metal.

The mould is placed in the casting machine. and a top plate is located and secured on top of the mould.

The lid of the casting machine is closed and the mould begins to spin. When it has reached the correct speed, molten pewter is poured into the mould.

The metal is poured carefully and continuously to ensure that the mould is filled and care is taken so as not to overfill the mould.

Once the figurines are cast, they have to be detailed.

A high speed drill with tungsten carbide bits is used to detail the figurines. The drill is similar to a dentist drill and as powered by compressed air. High speed steel bits can also be used.

Once the figurines are detailed they are polished in large vibrating tumblers using a technique developed by this company.

Rubber moulds can be used over and over again and providing care is taken, they will last for well over 100 spins.