a plastic base for use with a cylindrical flask for the elimination of wax patterns prepared for making metal castings by the lost wax process is identified . the base is made of a plastic material which is used in place of conventionally found rubber bases . the base is constructed of a thin - walled resilient plastic material and allows for direct set up of the wax patterns , as well as increased speed in the preparation of the plaster mold in the cylinder for making metal castings . the plastic base comprises an inner annular raised platform comprising a shoulder and the cylindrical flask is pressed on the shoulder deforming the plastic about the bottom edge of the flask to form a seal between the base and flask .