A thin configuration flat form glass envelope for use in vaccum tubes, incandescent lamps, fluorescent lamps and other electronic devices having elements which operate in a partial vacuum. In certain embodiments the envelope is comprised of a flat wall plate (14) and shaped wall plate (12) having a plurality of spaced-apart ridges (16, 18, 20) which project toward and in juxtaposition with the flat plate (14). The side walls of the ridges converge at a predetermined included angle and merge at a sharp apex that contacts the flat plate along a narrow path which produces minimal degradation of brightness uniformity across the envelope when light is transmitted through the shaped plate. Between the ridges a plurality of channels (28, 30) are formed containing an ionizable medium which is energized by electrodes to produce UV light which in turn is absorbed by a phosphor coating to emit visible light. In other embodiments the envelope is formed by two shaped plates joined together in facing relationship to form the channels.