photoengraving

[Pref. photo-, and Eng. engraving (q. v.).] 1. A term applied to proce es for producing printing blocks or plates by photography. The most commonly employed proce is to coat a metal plate with a thin film of asphaltum, and expose it to light under a reversed positive. The picture is next developed by di olving away the parts of the asphaltum not acted upon by the light, and the plate is subsequently etched in the usual way. This proce is sometimes called Photo-aquatint. The second method is more elaborate. A film of bichromatized gelatine, on a sheet of gla or a copper plate, is exposed under a photographic negative, and the unprinted portions which are soluble in water washed away, leaving the printed parts in relief. The plate with the relief is next coated with a film of silver by electro-deposition, and placed in an ordinary electrotyping bath, in which it is allowed to remain until a shell of copper from one sixteenth to one-eighth of an inch thick (according to size of plate) is formed. This, after the rough excrescences have been removed by filing, becomes the printing plate. It can be worked upon by an engraver, if nece ary, to remove photographic defects, and is printed on a copper-plate pre . When a relief block is required, a reversed negative is much greater extent. These proce es answer for subjects in black and white, as well as in colors. By printing from the half-tone block twice or more and having the impre ion slightly off register, beautiful results have been obtained. This is also the system by which conversion of the half-tones of a photograph into an ordinary printing block or plate has become so eminently succe ful. [PHOTOGRAVURE, PHOTO ELECTROTYPE.] 2. The proce making photo electrotypes. used to print from, and the etching is to [PHOTOGRAVURE.] IMG:content-1005.png:[blocks in formation] phō-tog -lỹ-phy, s. [Pref. photo-, and Gr. glyphō =to engrave.] The same as PHOTOGLYPHIC-ENGRAVING (q. v.). phô-tô-glyp-tic, a . [РноTO GLYPHIC.] *phô-tô-grăm, s. [Pref. photo- , and Gr. gramma =a letter, a drawing.] A photographic picture; a photograph. phô-tô-grăph, subst. [PHOTOGRAPHY.] A representation or picture of an object obtained by means of photography. "In the hope of finding many a sweet little spot for a photograph."- Field , Dec. 6, 1884. There is a copyright in photographs which is regulated by United States law. 3102