Newly devised counter-etch solution for making corrections on zinc printing plate.

Abstract

Contents of nautical charts should always be kept up-to-date by Notices to Mariners to provide navigators with latest information. Accordingly, it is necessary that the printing plates of those charts are also to be corrected for timely issue of updated prints. However, it has been experienced that making corrections of images on a zinc printing plate involves a difficult problem in connection with the counter-etch solution which is used to erase the images from the plate. Until now the nitric acid (HN03)-potassium alum (KAl(S04)2・12H20) solution has been used for this purpose, but it seemed that the action of this solution is more or less insufficient, and consequently the corrected image on the plate either rewritten with hand in lithographic writing ink or printed by photomechanical process is not strong enough, resulting in breaking or omission of printed images which makes a definite defect of such a publication as the nautical chart. In order to improve this problem, the author has newly devised a counter-etch solution with the following composition, with which a good result has been obtained: Chromic anhydride Cr03 200g Sodium sulfate Na2S04・lOH20 5g Nitric acid HN03 (s.p. 1.38) 38cc Water H2O 1,000cc

pH0.2