Ceramic casting mould and a method for its manufacture

A method of making a seamless ceramic casting mould with a thin outer wall comprising the steps of:

• making a first die, at least a part of which defines the shape of an article to be cast,
• providing within the die one or more high temperature disposable supports which support the thin outer mould wall during the firing process but which are disposable at a temperature at which the thin outer mould wall has acquired self-supporting strength,
• filling the die with a disposable pattern material whereby the supports become embedded in the pattern material, and allowing the pattern material to set,
• removing the disposable pattern from the first die and inserting it into a second die, the inner surface of which is dimensioned to conform generally with the outer surface of at least the article-defining part of the pattern and to define a space therewith which conforms to the required thickness of the outer wall of the mould,
• providing supports between the pattern and the die which are made from a ceramic material,
• injecting a ceramic material under pressure into the space and allowing it to set to form the outer wall of the ceramic casting mould, the inner surface of such outer wall defining the outer surface of the article to be cast,
• removing the disposable pattern from within the mould and firing the mould.