Material for moulding techniques

Polyvinyl chloride is made from rubber. There are different grades of flexibility and they all have their own colours so that it is clear to see the difference. PVC has a few advantages; The mould will not tear easily The mould can be cut up and reused when it is not needed any more Mixing materials is not required with PVC. There are also some disadvantages to using PVC; The material has to be handled when it is very hot The fumes are dangerous PVC can not ensure there will be a good standard of finish. Cold pour moulding compound Cold pour moulding compound is a silicone rubber that is flexible. It is in sealed containers and these containers must be kept in a metal container. It has a shelf life of roughly six months providing it is stored correctly. Cold pour is made of two chemical materials mixed together. One of the materials will need to be weighed out on scales, the other comes is a bottle that has the measurements down the side. Cold pour has a some advantages such as the mould does not tear easily and stays very flexible. It shows details from original moulds better than PVC will. It is also quite cheap, no expensive equipment is required. There are some disadvantages though. Materials must be weighed accurately. Cold pour needs to be stored in a specific way because of the chemicals. There is a fair amount of waste because it can not be cut and reused. Clay is used to seal leaks, support the moulds and it boards of clay are used to form a case over the mould. The clay is layed out on a wooden board that has French chalk on it to stop the clay from sticking. On each side of the wooden board are two pieces of wood that are the thickness that you want the clay. The clay is laid in between these two lengths and ruled in.