Page:Graphic methods for presenting facts (1914).djvu/351

 Of course, when line cuts are made from charts having a green-ink background, the printed illustration shows both the black and green-ink lines as black, and there is no distinction between the different lines. On this account, it is necessary for the person ordering the charts made from paper having green-ink lines to make certain that the main features of the chart stand out with prominent broad lines, so that there may certainly be a contrast in the width of the lines when printed, to make up for the contrast obtained in the original drawing by the difference in color of the two inks used.

Color printing is not yet ordinarily available unless a very large number of copies are to be made. In order to make areas stand out in contrast, different kinds of cross-hatching put on by hand ruling have been used very commonly. One trouble with the hand ruling is that it lacks uniformity unless done with very great care and to a scale considerably larger than the finished illustration, so that there may be enough photographic reduction to eliminate many of the defects which would otherwise appear. It is not widely known that there is a method available in the form of Ben Day mechanical shading, which is far superior to cross-hatching for line-plate work. Most good engravers can do Ben Day work, and it is just a matter of specifying what kind of shading is desired on the different portions of the drawing. With the Ben Day shading, more degrees of shading from light to dark are feasible than with hand work, and, in addition, there are many varieties of lines and patterns which may be used.

Since Ben Day work must be applied on each area separately by means of a transfer process, it is necessary for the engraver to make certain that the Ben Day shading shall not appear on some portion of the zinc plate where it is not desired. This requires that the engraver must protect the different portions of the zinc plate by a paint-like covering, and this must be done for each of the different kinds of shading used. It is almost impossible to make any square-inch price rate for Ben Day work because each new plate is a problem in itself. The work is ordinarily charged for on a time basis, the usual rates being from $1.00 to $1.50 per hour.

When copy to receive Ben Day work is sent to the engraver it is marked somewhat as shown in Fig. 233, so that the instructions to the engraver may be explicit. Crayon marks specify by number the kind of Ben Day shading desired, and arrows point to the different areas to be shaded. This marking of instruction is done with a blue