It is proposed that the high pH levels necessary to maintain the suspension rheology in investment casting pots leads to dissolution of the alumina particles causing coagulation of the colloidal silica. To reduce the pH level necessary for suspension stability, a colloidal silica-coated alumina particle was developed that looks like the common industrial material but has significantly longer pot lifetimes. The rheology of the pot appears stable for up to six time longer in a laboratory setting than a similar suspension prepared with conventional materials. The shell prepared with silica-coated alumina also produced more uniform shell microstructure and did not exhibit selective agglomeration of the silica commonly observed in shells produced with conventional raw materials.