Abstract: A device for high quality development of latent image on a strip of heat developable paper or film. The devices includes a heat conductive member which affords conduction of a uniform predetermined quantity of heat to all areas of the paper. The heat conductive member includes means to vent moisture from the paper to the atmosphere during the development process, to aid in bringing about uniform development of the paper or film. The heat conductive member may further include means to provide uniform pressure to the film or paper during the development process.