Abstract: A glow plug which includes an annular metal shell, thermally conductive tubular sheath, central electrode; resistance heating element, and electrically insulating, thermally conductive powder includes a glass seal in sealing engagement with the sheath and the electrode to form a sealed cavity within the sheath. The glass seal may include silicate, borate and borosilicate glasses, and may include one or more transition metal oxides, such as oxides of chromium, cobalt, nickel, iron and copper. The glass may also include a filler, including a ceramic oxide, such as one selected from a group consisting of quartz, eucryptites, leucites, cordierites, beta-spodumene, glass-ceramics, low-expansion glass(CTE<5 ppm/° C.), mullite, zircon, zirconia and alumina. The sealed cavity may house a protective inert gas.