Page:TheAmericanCarbonManual.djvu/85

From Wikisource
Jump to navigation Jump to search
This page has been validated.
FAILURES, FAULTS, AND REMEDIES.
75

An Uneven Texture in the Finished Print, some portions looking more glazed than the rest.—This defect arises from unequal and insufficient pressure in transferring. This unequal pressure may arise from the coating of India-rubber being uneven, or, more probably, from the coating of clear gelatine being applied in uneven streaks, or from uneven texture of blanket, or uneven pressure.

Portions or the Image tearing off in Transferring.—This will arise from the face of the print being imperfectly coated with gelatine, or from the paper or board to which the print is transferred having an imperfectly moistened surface, or from not being dry when the paper is removed, or soiled by fingering or dust.

A Green Tint Pervading the Blacks is caused by imperfect washing of the print, by which traces of soluble chromic salt are left in the image.

Unequal Sensitiveness.—This arises from the tissue having imbibed the bichromate solution unequally. If, in immersing the tissue, one portion remains dry while the rest is wet, that portion will be least sensitive, and will form a light patch in the picture. If the tissue is raised out of the bichromate in such a manner that streams of the solution run down the sheet, there will be in the print patches or streaks of a darker color, corresponding to the streams of the solution. The attachment of a strip of paper along the lower edge of the tissue, immediately after it has been hung up to dry, helps

    to abruptness in the transition from white to the lightest tint,—it is advantageous to expose the sheet for a moment to diffuse light, so as to produce a uniform tinting of the slightest degree possible. In vignetting, Mr. Swan regards this as almost indispensable. It may also be well to remark here, that the weakest tissue (No. 1) should be employed in vignetting, and that the vignetting screen should be very softly graduated in tint.