An insulated investment casting shell mold is made by first mixing at least one refractory material with a slurry vehicle forming a prime coat slurry, and optionally mixing at least one refractory material with a slurry vehicle forming a backup slurry. The prime slurry is coated onto a fugitive pattern and optionally dried and/or stuccoed wherein the stucco has at least one refractory material. Optionally, at least one coat of the backup slurry is applied to the prime coated fugitive pattern and optionally dried and/or stuccoed after each coat of the backup slurry. The backup and stucco may be applied a plurality of times to obtain a desired shell wall thickness. An insulating slurry is formed by introducing gas into a slurry vehicle having at least one refractory material and containing a stabilizer and a foaming agent wherein gaseous bubbles become entrained therein forming an insulating slurry having closed porosity therein. The insulating slurry is coated onto at least one portion of the pattern after the prime coat and preferably at least a portion of the outermost layer of a backup coated pattern has the insulating slurry thereon.