In accordance with the present invention, a method of electro-photographically manufacturing a luminescent screen assembly for a color CRT 10 on an interior surface of a faceplate panel 12 is described. A volatilizable, organic conductive (OC) layer 32 is provided on the interior surface of the panel and a volatilizable, organic photoconductive (OPC) layer 34 overlies the OC layer. The method includes the steps of: establishing a substantially uniform electrostatic charge on the OPC layer; exposing selected areas of the OPC layer to visible light to affect the charge thereon; developing the selected areas of the OPC layer with a triboelectrically charged dry-powdered, screen structure materials; fixing the screen structure materials to the underlying OPC layer with a suitable fixative; filming the screen structure materials; aluminizing the screen; and baking the aluminized screen. The present method is an improvement over prior methods because the relative humidity (RH) during the charging step is maintained above a humidity level below which the performance of the OC layer is negatively impacted by a reduction in its ion transfer mobility which makes it difficult to apply a usable corona charge to the overlying OPC layer, and below a humidity level above which the OC layer swells causing cracking in the OPC layer. Additionally, the RH during the development step is maintained below a humidity above which the screen structure materials can absorb water and macro-agglomerate, thereby changing the charge-to-mass ration of the screen structure materials to a value which adversely affects the deposition thereof.