LITMIR.BIZ

      Published by Good Press, 2019

       [email protected]

      EAN 4064066183776

Table of Contents

       TRANSLATOR’S PREFACE.

       CHAPTER I.

       CHAPTER II.

       CHAPTER III.

       CHAPTER IV.

       CHAPTER V.

       Ink and Paper.

       CHAPTER VI.

       CHAPTER VII.

       Stripping the Film off Gelatine Negatives for Collotype.

       CHAPTER VIII.

       CHAPTER IX.

       CHAPTER X.

       CHAPTER XI.

       IN THE PREPARATION OF THE PLATES.

       FAILURES IN PRINTING.

       CHAPTER XII.

       CHAPTER XIII.

       CHAPTER XIV.

       CHAPTER XV.

       CHAPTER XVI.

       CHAPTER XVII.

       CHAPTER XVIII.

       THE BITUMEN METHOD.

       DIRECT PHOTO-LITHOGRAPHY.

       PHOTO TRANSFER FROM PAPER.

       CHAPTER XIX.

       CHAPTER XX.

       Transposing—Black and White.

       Engraved Negatives for Photo-lithography.

       APPENDIX.

TRANSLATOR’S PREFACE.

       Table of Contents

      The impossibility of obtaining any work in the English language on the subject of Collotype first led to my translation of the German work of Dr. Schnauss, and the fact that no work has hitherto appeared fully dealing with the matter is the excuse I offer for the present publication. The translation is necessarily one of considerable freedom, but it is offered as containing all the information to be found in the original, and in addition, considerable extensions, made with the author’s consent. The omission of the chapter dealing at length with the steam machine was necessitated by the fact that the rotary machine there described is no longer manufactured.

      Without pointing to the frontispiece in any sense as a high-class work, it may serve to show that I have made some practical acquaintance with the subject. The illustration, printed on ordinary paper, was produced from the instructions found in this work, and I may add that at the time of writing I have printed over 500 impressions from the first plate, and it still remains in fair working condition.

      EDWIN C. MIDDLETON.

      Stanmore Road,

       Birmingham.

       COLLOTYPE AND PHOTO-LITHOGRAPHY.

CHAPTER I.

       Table of Contents

      Introductory.

      THE observation by Mungo Ponton of the sensitiveness to light of bichromate of potassium in conjunction with organic substances is but little more recent than the discovery of photography itself. If sized paper is saturated with an aqueous solution of this salt and then exposed under any transparent design, the latter will be reproduced as a negative of a brown colour on a yellow ground. If the exposed paper is placed in water, the bichromate salt will be removed from the unexposed, and consequently unaltered portions; the image will remain brown after this treatment, though somewhat bleached. The sensitiveness to light is proportionately increased by the addition of larger quantities of organic substances, as starch, paste, glue, sugar or gum, as first observed by Becquerel. This arises in consequence of the organic matter being oxidised by the chromic acid, a corresponding decomposition and reduction of the chromate salt to chromate of chromium taking place.

In the year 1853 an Englishman—Fox-Talbot, the gifted discoverer of calotype (i.e., the production of photographic negatives on paper by means of silver salts)—followed up the lines of these important observations, and discovered that the mixture of bichromate of potassium and glue entirely lost its solubility and power of swelling in cold water after exposure to light, and on this he based his process (heliography) of etching on metal plates. The plate, after receiving a coating of the chromated gelatine solution, was dried, exposed under a positive, and afterwards developed or washed out in warm water, all unexposed and consequently soluble portions being removed, while the exposed and therefore insoluble portions covered as a negative[A]

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