A Manual of Photographic Chemistry, Including the Practice of the Collodion Process

by T. Frederick Hardwich

[CHAPTER IV.]

THE PRACTICAL DETAILS OF PHOTOGRAPHIC PRINTING.

This Chapter is divided as follows:—

Section I.—The ordinary direct process of positive printing.
Section II.—Positive printing by development.
Section III.—The mode of toning Positives by Sel d'or.
Section IV.—On printing enlarged or reduced Positives, transparencies, etc.

SECTION I.

Positive Printing by the direct action of Light.

This includes—the preparation of sensitive paper,—of fixing and toning Baths,—and the manipulatory details of the process.

Selection of Paper for Photographic Printing.—The ordinary varieties of paper sold in commerce are not well adapted for the production of Positive prints. Papers are manufactured purposely which are more smooth and uniform in texture. Many samples of even the finest paper are however defective, and hence each sheet should be examined separately by holding it against the light, and if spots or irregularities of texture are seen, it should be rejected. These spots usually consist of small particles of brass or iron, which, when the paper is rendered sensitive, decompose the Nitrate of Silver and leave a circular mark very noticeable after fixing.

The foreign papers, French and German, are different from the English. They are porous and sized with starch, the English being sized with gelatinous animal matter. In all cases there is a difference in smoothness between the two sides of the paper, which may be detected by holding each sheet in such a manner that the light strikes it at an angle; the wrong side is that on which dark wavy bands, of an inch to an inch and a half in breadth, are seen, caused by the strips of felt on which the paper was dried. With most qualities of paper no difficulty whatever will be experienced in detecting the broad and regular bands above referred to; but when they cannot be seen, the wrong side of the sheet may be known by wire markings crossing each other, or if the paper be wetted at the corner, one side may appear evidently smoother than the other.

PREPARATION OF SENSITIVE PAPER.