Printing and bookbinding for schools . ial nitric acid is the safest solution. It is diluted bvadding about an ecjual volume of water to it, making itfrom 15% to 20% strong. The diluted acid is poured intoa glass or porcelain tray and the plate put into it. If theacid can be kept moving by frequently rocking the trav, theetching will be ^•ery materially hastened. It takes fromthree to five hours to etch deeply a piece of copper, de-pending upon the strength and amount of the solution andthe amount of exposed surface to be eaten away. If largesurfaces are to be etched, quite a large quantity of
Printing and bookbinding for schools . ial nitric acid is the safest solution. It is diluted bvadding about an ecjual volume of water to it, making itfrom 15% to 20% strong. The diluted acid is poured intoa glass or porcelain tray and the plate put into it. If theacid can be kept moving by frequently rocking the trav, theetching will be ^•ery materially hastened. It takes fromthree to five hours to etch deeply a piece of copper, de-pending upon the strength and amount of the solution andthe amount of exposed surface to be eaten away. If largesurfaces are to be etched, quite a large quantity of acid isdesirable, or else a changing or strengthening of the solu-tion during the process. As soon as the acid becomes some-what burdened with the metal, it ceases to act at all freely,and even begins to deposit a blue nitrate upon the such a case, it is best to put the plate into a fresh so-lution. Care must be taken that the acid is not too strong, asthe heat, generated bv its rapid action softens the varnish 54 PRINTING. FIG. 29. WOOD CUTS AND METAL PLATES 55 and lets the acid under to play havoc with the design. Xu-nierous bubbles and yellow-green fumes indicate that theacid should be weakened by the addition of a small quan-tity of water. By observing the progress of the etching occasionally,it can be told when the proper depth has been the plate is heated sufficiently to soften the varnish,soaked in kerosene or turpentine, and rubbed clean with acloth. Or the warm varnish can be removed by simplvsaturating the cloth with kerosene, turpentine, or benzineand rubbing over it. A block of wood is then prepared for a base so thatthe mounted plate is slightly less in thickness than theheight of the type. Then with a punch or a small drill,holes are put into the lower, or background, part of themetal. Through these holes the plate is fastened to theblock by small tacks or escutcheon pins, the heads beingsunken below the surface of the background. Large su
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License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubj, booksubjectbookbinding
