This disclosure relates generally to methods and apparatus for investment casting of a metallic component, and to methods and apparatus for producing ceramic casting cores in particular. The method of producing an investment casting ceramic core is provided that includes: providing a core body consisting of a leachable material; surrounding the core body with a mold composition within a vessel, which mold composition is configured to solidify; leaching the core body from the mold composition subsequent to the mold composition solidifying, thereby leaving an internal cavity within the solidified mold composition; depositing a ceramic composition within the internal cavity of the solidified mold composition; sintering the ceramic composition to a solid ceramic core; and removing the solid ceramic core from the mold composition. The ceramic core mold composition includes one or more body constituents that include at least one refractory material in particulate form, and one or more solidifying constituents configured to solidify the mold composition in a dimensionally stable form around a core body consisting of a leachable material. The one or more body constituents may include one or more of alumina, crystalline silica, or magnesia particulates. The one or more solidifying constituents may include a binder configured to bind the at least one refractory material in particulate form into a solid. The binder may include at least one of a poly-vinyl alcohol, a sodium silicate, a polyethylene glycol, an aqueous solution of starch, or a poly-acrylate. The solidified mold composition is configured to remain in a solid form, including an internal cavity subsequent to leaching of the core body. The solidified mold composition is configured to transform from the solid state to a non-solid form during a sintering process. The mold composition may transform from the solidified mold composition to a loose particulate form during sintering. During the sintering step the mold composition may change to a form that permits the sintered ceramic composition to be removed undamaged from the vessel. During the sintering step the ceramic composition may be configured to cause the one or more solidifying constituents to depart from the vessel and remaining mold composition constituents within the vessel in a loose particle form. The one or more solidifying constituents are configured to depart from the mold composition during the sintering process.