A chamber for processing fluorescent lamp cathodes has a dividing wall with openings receiving the unsealed exhaust tube of the glass stem on which the cathode is supported. Adjacent each opening are conductors connecting the cathode leads to an adjustable source of heating current. While heating the cathodes at scheduled currents, a controlled flow of inert gas, e.g. nitrogen, enters the inlet portion of the chamber on one side of the wall thence through the exhaust tube of each stem past the cathode on the stem in the outlet portion of the chamber on the other side of the wall. The controlled flow of gas allows a carbon dioxide atmosphere at the cathode during reduction of alkaline earth metal carbonate on the cathode to its oxide, while the gas flow provides an otherwise inert environment.