Page:TheAmericanCarbonManual.djvu/26

 the back of the photographically-impressed portions required to be washed away, and the employment of paper in the way it has been employed hitherto, not only as a means of supporting the colored coating, but also to form ultimately the basis or groundwork of the print, obstructed the removal of the inner or back portions of the colored coating, and prevented the obtaining of half-tone.

“Now, my invention consists in the formation of tissues adapted to the manner of printing referred to, and composed of, or prepared with, colored gelatinous matter, and so constructed, that while they allow, in the act of printing, free access of light to one surface of the colored gelatinous matter, they also allow free access of water, and the unobstructed removal of the non-affected portions of the colored matter, from the opposite surface, or back, in the act of developing; and I obtain this result either by the disuse of paper altogether, or by the use of it merely as a backing or temporary support of the colored gelatinous matter; the paper, so used, becoming entirely detached from the colored gelatinous matter in the act of developing, and forming no part of the print ultimately.

“My invention consists, furthermore, in the special mode of using the said tissues, whereby superior half-tone and definition in the print are obtained as aforesaid, and also in a mode of transferring the print, after developing, from a temporary to a permanent support, so as to obtain a correction in the position of the print in respect of right and left. In producing the photographic tissues referred to, I form a solution of gelatine, and for the purpose of imparting pliancy to the resultant tissue, I have found it advisable to add to the gelatine solution, sugar or other saccharine matter, or glycerine. To the said gelatinous solution I add carbonaceous or other coloring matter, either in a fine state of division, such as is used in water-color painting, or in the state of a solution or dye, or partly in a fine state of division, and partily in solution.

“With this colored gelatinous solution I form sheets or films, as hereafter described; and I render such sheets or films sensitive to light, either at the time of their formation, by introducing into the gelatinous compound bichromate of ammonia, or other agent of like photographic properties, or by applying to such non-sensitive sheets or films, after their formation, a solution of the bichromate, or other substances of like photographic property. This latter method I adopt when the sheet or film is not required for use immediately after its formation. I will, in my future references to the bichromate of ammonia or the bichromate of potash, or to