Most mother moulds need to be a two piece casing which needs to be fastened together around the latex mould. You will need to find the easiest parting line for the two pieces to separate from the mould. This is usually on the less detailed areas of the mould. Once you have decided where your parting line should be mark it out with a pen on the latex mould.Now you can make your first half of the mother mould. Using non-hardening oil based clay build up a wall up to the parting line. Make this wall about 50mm in thickness and add some grooves into the wall to act as a registration point so that the two mould pieces will slot together in the correct place.air cooler mouldPlaster can now be applied to the first half of the latex mould right up to the clay walls. Make sure the clay walls with the registration grooves are covered with plaster. Small squares of hessian can be soaked in the plaster and added to the plaster already on the mould to add strength to the mother mould. Make sure you overlap these hessian squares. Build up the plaster mother mould until it is about 15 to 30mm in thickness and allow drying.Once the plaster has set you can remove the non-hardening clay. You will now need to apply a release agent to the plaster which was left with registration grooves when the clay was removed as we will now add the second half of the mould. If no release agent is applied to this part of the first mother mould piece the plaster will stick to the second half. We can use petroleum jelly for this.Now apply plaster to the second half of the mould in the same method as the first piece with hessian for strength. Once this second piece has set both halves of the mother mould can be removed. These pieces should come away easily. The mould support is now complete. The original model can be removed from the latex mould and casting material can be poured in. Thick rubber bands can be used to hold the plaster mother mould pieces together while casting.
