Disclosed herein is a conversion kit whereby building or plant signs illuminated by incandescent bulbs or fluorescent tubes may be converted to electroluminescent illumination. The kit includes an electroluminescent panel and an opaque sign mask, The opaque sign mask is adapted to overlie the electroluminescent panel and the sign indicia of the mask are in the nature of stencil like cutouts to allow the light emitted by the underlying electroluminescent panel to pass only through the indicia cutouts.