A spark plug includes an insulative sleeve. A glaze coating is disposed on an exterior surface of the insulative sleeve. The glaze coating includes a boric acid, a borosilicate glass, a barium borate glass, a phosphorous glass, a silicate glass, or a combination thereof. The glasses are independently modified with a modifier selected from the group consisting of alkali group metals, alkali earth group metals, aluminum, silicon, a halogen, or a combination thereof. The glaze coating has a softening point between about 650° C. and about 1100° C.