Excerpt from A Manual of Photoengraving: Containing Practical Instructions for Producing, Photoengraved Plates in Reliefline and Half-Tone This work is a revision of the "Manual" which appeared several years ago. While retaining the features of the first edition that hold good to-day, it presents a number of new formulae and more complete descriptions of the processes involved. My purpose has been to provide a practical guide that might be an aid to the beginner, and a useful book of reference for the more advanced worker. With this object in view I have, therefore, entered fully into the description of the details of the various operations, and have presented an outline of the chemical principles underlying the methods considered. The importance of a study of the scientific laws upon which the practical work is based can not be too strongly emphasized. It is the possession of this knowledge that makes the difference between the intelligent investigator and the "rule-of-thumb" workman, and the student is urged to give ample attention to these fundamental principles. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works."