A method for producing a spark plug, the spark plug comprising a center
electrode, a metal shell and an alumina ceramic insulator disposed
between the center electrode and the metal shell, wherein at least part
of the surface of the insulator is covered with a glaze layer, the method
comprising the steps of: preparing a plurality of kinds of element glaze
powders wherein each kind of the element glaze powders has a different
dilatometric softening point and a different linear expansion coefficient
compared to other kinds of element glaze powders; coating a surface of
the insulator with the plurality of kinds of element glaze powders so as
to form a glaze powder layer; and baking the glaze powder layer to the
surface of the insulator so as to form the glaze layer by heating the
glaze powder layer.