Abstract: Defects in green, unsintered ceramic casting cores which contain a thermoplastic binder are repaired according to this invention. In a preferred embodiment, a mixture of a volatilizable solvent and ceramic particles are applied to the defect. The solvent softens the binder in the core, and the loose ceramic particles patch the defect area. After the solvent volatilizes, the binder hardens and binds the newly applied particles to the core. Then, the repaired core is heated to a first temperature to volatilize the binder, and then to a second, higher temperature to sinter the ceramic particles to each other.

Abstract: The surface of green (unsintered) casting cores which contain ceramic particles and a thermoplastic binder are bonded to each other by softening the binder in each core and applying a layer of ceramic particles to the surface of at least one of the cores to be joined, assembling the cores to each other such that the core surfaces are in close contact with each other; causing the binder to reharden; and then heating the cores to volatilize the thermoplastic binder and to sinter the ceramic particles in the cores to each other.