Method of shell molding

Claim 1

THE PROCESS OF PREPARING A SHELL MOLD COMPRISING APPLYING TO A HEATED METAL SURFACE A LOOSE FIRST MIXTURE OF SAND AND A THERMOSETTING RESIN, PERMITTING THE RESIN PORTION OF THIS SAND-RESIN MIXTURE ADJACENT THE HEATED METAL SURFACE TO CURE AT LEAST SUFFICIENTLY TO PRODUCE A THIN, SELF-SUPPORTING LAMINA OF SAND-RESIN, MIXTURE, EXCESS OF NON-ADHERING LOOSE FIRST SAND-RESIN MIXTURE, PERMITTING THE RESIN IN THE SAND-RESIN LAMINA TO CURE FURTHER, REAPPLYIMG A LOOSE, SECOND SAND-RESIN MIXTURE TO SUBSTANTIALLY THE ENTIRE AREA OF THE ROUGH SURFACE OF THE THIN LAMINA, MAINTAINING THIS LOOSE, SECOND SAND-RESIN MIXTURE IN CONTACT WITH THE THIN LAMINA UNTL THE DESIRED THICKNESS OF SHELL HAS BEEN PRODUCED, REMOVING THE EXCESS LOOSE, SECOND SAND-RESIN MIXTURE AND CURING THE LAMINTED MOLD FORMED, SAID FIRST SAND-RESIN MIXTURE COMPRISING SAND SUBSTANTIALLY FINER THAN THE SECOND SANDRESIN MIXTURE.