In order to produce various stainless steel castings, a new ceramic mold making process based on full mold EPS patterns has been developed. In this method, a ceramic shell approximately 10 mm in thickness is created by applying a coating to EPS pattern, which is then heated in a furnace in order to gasify the EPS pattern and harden the ceramic shell coating. Unlike the Replicast process, the ceramic shell thus formed requires neither a vacuum nor back up sand for the pouring, and being pre-heated, is not subject to thermal stress. The strength of the ceramic shell at high temperatures is very important since support sand is not used. A trace of the x-ray diffraction measurements revealed that the cristobalite peak occurs at 21.9°. When the ratio of fused silica is increased, the cristobalite intensity rises significantly and the post-cooling bending strength decreases. It is thought that because fused silica transforms into cristobalite, a large thermal contraction occurs during the cooling period owing to the decrease in bending strength, and as a result, many fine cracks are generated throughout the ceramic material. The results suggest that the most suitable refractory material for the ceramic mold is a 1 : 1 mixture of zircon and fused silica. On this basis, pre-heated ceramic molds have been used without back-up sand to produce various stainless steel castings.