CASTING

They broke the mould........

With the discovery of the metal, bronze, and finding that it could not be hammer forged, a way of shaping the metal had to be found. Because bronze melts at a relatively low temperature, compared with other metals, you have liquid that can take up the shape of whatever you pour it into.

With the transition from Neolithic to Bronze age, one of the first objects to be copied into the new technology was one of the the great status symbols, an axe head.

Open casting
So....... to make a hollow in a mouldable material (that will not burn!), you hammer out the shape of an axe-head in the surface of a flat piece of stone, set it up level, and pour your molten bronze into the hollow. Let it cool and tip it out.

This was all right, but it produced a very 2 dimensional object, It is difficult to make anything with thickness, as one side (the one on the top of the mould) is always flat!

The next idea was to make two moulds that were mirror images of each other, making a channel into the thick end of the object. Fit the two halves together face to face and bind with wet leather (it shrinks as it dries and holds the mould tightly). Stand the mould upright with the opening of the channel at the top. Pour your bronze into the mould and wait until it cools.

This method works quite well, but, the object you are making cannot be very intricate, so a new way of mould making was developed

Lost Wax Casting
First you have to start at the other end of the process.

Carving a piece of wax into a life size model.
Make the mould around the model, using clay
Fire the clay, and at the same time melt the wax out of the mould (The graphic shows a cutaway example) Pour the molten bronze into the mould
Smash the clay off the bronze and clean and polish the casting