A mercury dispenser for electric discharge lamps consists of welding a small metallic member (16) in the form of a "patch", to a portion of the surface of the cathode disintegration shield (10) and trapping a predetermined volume of mercury under the "patch". A dimple (17) may be formed in the shield (10) or in the member (16). The shield (10) may be formed from a continuous strip which is dimpled at a predetermined pitch, the dimples filled with mercury and the "patches" (16) welded over the dimples. The strip can then be cut into discrete "patched" sections to be bent into shields and assembled with the cathode structure. The mercury is liberated from under the "patch" by heating and vaporization, the vapor pressure forcing the "patch" open.