Abstract: A method of forming a ceramic investment shell mold about a fugitive wax pattern of an article comprises coating the pattern with ceramic slurry, applying a ceramic particulate material heated above ambient temperature to the slurry layer, drying the ceramic slurry layer with ceramic particulates thereon, and repeating said coating, applying and drying steps to build up a shell mold on the pattern. The ceramic slurry with ceramic particulates thereon is dried initially dried for a time using relatively low humidity flowing air at an air temperature above about 80 degrees F. and then subsequently for a time using relatively low humidity flowing air at an air temperature not exceeding about 80 degrees F. Ceramic investment shell molds can be built-up in times typically less than 10 hours by practice of the invention with substantially reduced incidence of shell mold cracking during the shell mold building process and subsequent pattern removal operation.

Abstract: A document card reader including a row of light sources transmitting light through a corresponding series of column-like cavities within a pair of members between which a document card with punched openings therethrough may move and a convex lens placed so as to receive light transmitted through the document card openings and transmit the light from all of the openings to a photodetector positioned at substantially the focal point of the lens.