Patent ID: 7370688

Claim:
A method of manufacture of a multilayer ceramic shell out of a master pattern of a part to be manufactured, said method comprising the steps of: preparing a first slip containing ceramic particles and a binder, wherein the first slip comprises mullite flour in an amount ranging between 65 and 80 in weight %, dipping the master pattern in said slip and forming a contact layer, and depositing sand particles on said contact layer and drying said contact layer, wherein said sand particles are mullite grains having a grain size distribution range between 80-250 micron, wherein the first slip does not contain any zircon and the first slip comprises a wetting agent, a liquefier and a texturing agent, forming additional layers on said contact layer thereby forming a ceramic shell; disposing of said master pattern thereby forming a ceramic mould; baking said ceramic mould; casting a metal part in said ceramic mould; wherein said contact layer forms an interface between said ceramic mould and said metal part, and wherein said additional layers comprise a mixture of alumina and mullite flours in amounts ranging between 45 and 95% in weight, and mullite grains in amounts ranging between 0 and 25% in weight.