blade or other rotating blade mixer for several minutes to achieve uniformity concentrated 75 phosphoric acid is then added in a ratio of about 1 3 pounds to approximately 3 2 pounds of the dry mixed powder of the previous step this composition is thoroughly mixed to a mushy consistency and then dumped from the mixer a predetermined volume of the mix which is dependent upon the size of the product to be molded is placed in the cavity of a heated compression mold in this case the product is a standard switch insulator part known as an arc chute roughly rectangular in shape being about 9 inches long 2 inches wide and 1 4 to 7 16 inch in thickness which varies in different parts of the product the molding press capacity will vary with the size of the part but for the arc chute described above a clamping pressure of about 3 tons is required the mold is closed to compress the molding composition into close conformation with the mold surfaces and is maintained closed for a cure interval adequate to achieve a required preliminary hardness or aging of the molded part in this example the cure time is approximately 3 minutes after which the mold is opened and the molded piece removed the piece is typically then subjected to a post bake in an oven to complete the curing process the part is then ready for final dressing or finishing and packing for shipment the product has a hard dense fine grain surface of the type desired for electrical or thermal insulator purposes the same procedure as that of example 1 is followed but the proportioning of the ingredients.