Abstract: The mercury-vapor pressure within a fluorescent lamp is controlled by a metal (indium or an alloy of indium and tin, for example) that wets glass, combines with the mercury within the lamp to form an amalgam and is divided into segments which are fused directly to one or both of the glass stems at spaced locations. The amalgamative-metal segments are of such shape and mass that they inherently remain in place on the stem when they are heat-softened and pressed onto the glass surface. Segments of larger size and mass are retained in place by an overlying porous layer of inert material that adheres to the glass or by an embedded wire mesh member and an exterior porous coating of inert material. The amalgamative metal can also be combined with a fusible binder to form a composite which is divided into small pellets that are pressed onto the glass stem and held in place by the adhesive action of the binder when the latter is fused during the bulb-lehring operation required to fabricate the lamp.