This important branch of the art will require only a short chapter, not because we underrate its merits, but because nearly all that has been said on drawing and printing on stone, is equally applicable to working on metal plates, and consequently no necessity exists for extending the previous instructions on those points.

146. The Principles of Zincography are almost identical with those of lithography; and all ordinary styles of drawing may be performed upon zinc plates instead of on stone; the chief distinctions being that blacklead pencil-marks are apt to roll up in printing, and that the two- and three-line lettering-gauges used by copperplate engravers may be used to mark direct upon the zinc. The materials used are the same, and the mode of printing is identical. Zinc plates have the advantage over large stones, in being less in first cost, and being much more portable. Hence, they are used very extensively in many printing establishments for a variety of work; the chief among which, it may be mentioned, are large plans and wall-advertisements. As neither ink, crayon, nor gum penetrates the zinc in the same manner as they do stone, the printing is more liable to accident, and requires great attention and skill on the part of the printer. One very marked difference between the zinc and stone, is that the former is subject to oxidation by contact with a moist atmosphere. For this reason, great care must be exercised in drying the plates off’ quickly after their preparation for drawing, and during the printing, to prevent the gummy preparation from being actually removed.