Photostat
a trade name for direct photographing process. By this means copies of drawings, legal papers, records, etc. may be rapidly produced. A special camera, with special developing and fixing attachments, is used in the process. The reproductions are made directly upon the surface of the print paper, which has been coated with a special emulsion. In order that the image will not be reversed the camera is fitted with a reversing prism and a special copying lens. The entire apparatus of the camera and developing plant is self-contained. After exposure the paper passes through the developing and fixing process, and is then cut and dried and is ready for use.
The ordinary photostat print is white upon a black background, but by a slight addition to the process, black prints upon light backgrounds are secured. The process is much used for legal work, cess is much used for legal work, duplicating policies, in insurance, and particularly in engineering work, where many copies of the same plans are desired. The scale of the drawing made may be easily altered. light rays to the treatment of such dis-