Patent ID: 8235092

Claim:
A method of making an insulated investment casting shell mold comprising the steps of: mixing at least one refractory material with a first slurry vehicle to form a first slurry; coating a fugitive pattern of an article to be cast with said first slurry forming a coated fugitive pattern having an innermost layer; providing a second slurry vehicle; mixing at least one refractory material with said second slurry vehicle to form a second slurry; adding at least one foaming agent and at least one stabilizer to said second slurry; introducing small, stable gas bubbles, compared to gas bubbles formed by the foaming agent alone, into said second slurry containing said foaming agent and said stabilizer; entraining said small, stable gas bubbles in said second slurry containing said foaming agent and said stabilizer thereby causing said second slurry to maintain said gas bubbles to form a bubbled insulating slurry; applying said bubbled insulating slurry to at least a portion of said coated fugitive pattern to form an insulating portion having closed porosity therein; drying said insulating portion; removing said fugitive pattern from said innermost layer forming a green shell mold; and firing said green shell mold to form said insulated investment casting shell mold with a reduced thermal diffusivity as a result of said closed porosity thereby slowing the cooling of material cast within said insulated investment casting shell mold.