The first step to do a god work in a foundry is to have a good mould. the mould is a negative made generally with plaster and rubber (siliconic or other kind) that we need to make a wax copy of the model that the sculptor give us. Is not so easy as it seems to make a mould that will have the right characteristics. Most of the time the model is very intricate , sometime so complicate that to simplify the operation of negative making the model need to be cutter or divided in several parts , so from a single sculpture we have to do several moulds. the different pieces will be welded again together in wax. Even more complicate is when the model can not be divided for different reasons ,maybe is an ancient model or is made in a material (stone, glass….) that cannot be repaired after the operations.
the first operation to make a mould is to put on the model some protective wax or oil to prevent any damage of it. then will be applied the first layer of rubber and others will follow to make a good thickness . after this the plaster will be applied not in just one layer but in several one and in different times, in manner that the mould will result as a 3d puzzle , so at the moment of the extraction of the wax from inside, the delicate model will have no damage at all.
To make a mould in the proper way require a lot of experience, because each project is a unique and in the end to make it you have to apply a principle instead of making a standard series of actions.
A good mould will ensure the good realization of the wax with all the details of the sculptor’s model , no deformation and will simplify a lot the following operation to obtain a metal sculpture.
see you next week