Photography - 1852 Author:Robert Hunt Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER IV. ON THE GENERAL MODES OF MANIPULATION ADOPTED IN THE PREPARATION OF SENSITIVE PAPERS AND THE MORDANT BASES. The only apparatus required by the p... more »hotographic artist for the preparation of his papers, are, some very soft sponge brushes and large camel-hair pencils (no metal should be employed in mounting the brushes, as it decomposes the silver salts), a wide, shallow vessel, capable of receiving the sheet without folds, and a few smooth planed boards, sufficiently large to stretch the paper upon, and a porcelain slab. He must supply himself with a few sheets of good white blotting paper, and several pieces of soft linen, or cotton cloth, a box of pins (the common tinned ones will answer, but, if the expense is not a consideration, those made of silver wire will do better), and a glass rod or'two. The materials necessary to produce all the varieties of sensitive paper which will be brought under consideration in this section are— 1. Nitrate of Silver. The crystallized salt should, if possible, always be procured. The fused nitrate, which is sold in cylindrical sticks, is more liable to contamination, and the paper in which each stick of two drachms is wrapped being weighed with the silver, renders it less economical. A preparation is sometimes sold for nitrate of silver, at from sixpence to ninepence the ounce less than the ordinary price, which may induce the unwary to purchase it . This reduction of price is effected by fusing' with the salt of silver a proportion of some cupreous salt, generally the nitrate. This fraud is readily detected by observing if the salt becomes moist on exposure to the air—a very small admixture of copper rendering the nitrate of silver deliquescent. The evils to the photographer are, want of sensibility upon exposure, and the peri...« less