A molybdenum electrode is mounted in a stepped aperture in the sidewall of the forehearth such that the inner end portion of the electrode is immersed in the molten glass where the molybdenum is effectively isolated from oxidizing agents. The outer end portion of the electrode is shielded in a high temperature alloy steel sleeve, which sleeve is spaced from the electrode to provide an annular space therebetween. A ceramic fiberous material is provided between the inner end of the sleeve and the electrode, and a high temperature alloy steel plug is threadably secured to the outer ends of both the sleeve and the electrode to seal the outer end of this annular space, and to serve as an electrical terminal for the electrode. The molten glass solidifies inside the sleeve's inner end to seal the inner end of the sleeve. The assembly is clamped to the furnace framework by an insulated bracket adjacent the outer end of the sleeve, which bracket is designed to thrust the assembly inwardly so that an annular flange on the sleeve abuts the sidewall of the refractory channel, which sidewall defines the step in the aperture of the furnace forehearth sidewall itself.