Methods for fabricating wires insulated by low porosity glass coatings are provided, as are high temperature electromagnetic (EM) devices containing such wires. In embodiments, a method for fabricating a high temperature EM device includes applying a glass coating precursor material onto a wire. The glass coating precursor material contains a first plurality of glass particles having an initial softening point. After application onto the wire, the glass coating precursor material is heat treated under process conditions producing a crystallized intermediary glass coating having a modified softening point exceeding the initial softening point. The crystallized intermediary glass coating is then infiltrated with a filler glass precursor material containing a second plurality of glass particles. After infiltration, the filler glass precursor material is heat treated to consolidate the second plurality of glass particles into the crystallized intermediary glass coating and thereby yield a low porosity glass coating adhered to the wire.