Processing Systems for Autopositive Paper in Office Copying*

Abstract

The porous-block system of stabilization processing Autopositive paper was introduced some eight years ago, and was superseded by small motor-driven machines using a two-bath immersion system. With the aim of increasing the processing rate and simplifying the processing machines so that very lightweight papers could be handled, experimental monobaths were evolved. These gave promising results, but the monobath was eventually abandoned in favour of a two-solution system with surface-application processing. With such a system a processing rate of lO ft/min has been achieved, using a high pH developer, and a stabilizer based on thiocyanate. The tendency for thiocyanate to attack the silver image on keeping the processed print has been overcome by the use of chemical inhibitors in conjunction with a surface-application processing technique. The design of the processing machine makes use of the natural curl of the wetted paper to prevent wrap around the rollers, very light-weight papers being handled without difficulty. Using a thin base a special Autopositive paper for bireftex exposures has been introduced, providing a cheap method of obtaining right-reading positive (black-on-white) copies from any original, using only a single sheet of paper.