An induction furnace apparatus and method for reducing the magnetic field produced by the operation of the furnace. The induction furnace including a refractory vessel, an induction coil, and an outer shell having a layer of metallic and magnetically permeable material. The metallic and magnetically permeable material comprising a plurality of elements having a shape and size that is chosen to maximize the packing density of elements throughout the layer. The outer shell further including a top, base, and sidewall arranged about the refractory vessel such that the metallic and magnetically permeable material is formed between the refractory vessel and the outer shell. The invention provides a method for casting metallic and magnetically permeable material with or without a non-conductive matrix. The castings can be formed into inserts or incorporated into the top, base, and side wall of the outer shell. The invention includes inserts comprising metallic and magnetically permeable material located in a space formed between the refractory vessel and the outer shell.