Third:  Have the values few and positive.  It is necessary to keep the gray tones pretty distinct to prevent the relation of values being injured, for while the gray tones darken in proportion to the degree of reduction, the blacks cannot, of course, grow blacker.  A gray tone which may be light and delicate in the original, will, especially if it be closely knit, darken and thicken in the printing.  These rules are most strictly to be observed when drawing for the cheaper classes of publications.  For book and magazine work, however, where the plates are touched up by the engraver, and the values in a measure restored, the third rule is not so arbitrary.  Nevertheless, the beginner who has ambitions in this direction will do well not to put difficulties in his own way by submitting work not directly printable.

[Side note:  Some Fanciful Expedients]

There are a number of more or less fanciful expedients employed in modern pen work which may be noted here, and which are illustrated in Fig. 10.  The student is advised, however, to resort to them as little as possible, not only because he is liable to make injudicious use of them, but because it is wiser for him to cultivate the less meretricious possibilities of the instrument.

“Spatter work” is a means of obtaining a delicate printable tone, consisting of innumerable little dots of ink spattered on the paper.  The process is as follows:  Carefully cover with a sheet of paper all the drawing except the portion which is to be spattered, then take a tooth-brush, moisten the ends of the bristles consistently with ink, hold the brush, back downwards, in the left hand, and with a wooden match or tooth-pick rub the bristles toward you so that the ink will spray over the paper.  Particular, care must be taken that the brush is not so loaded with ink that it will spatter in blots.  It is well, therefore, to try it first on a rough sheet of paper, to remove any superfluous ink.  If the spattering is well done, it gives a very delicate tone of interesting texture, but if not cleverly employed, and especially if there be a large area of it, it is very likely to look out of character with the line portions of the drawing.

A method sometimes employed to give a soft black effect is to moisten the lobe of the thumb lightly with ink and press it upon the paper.  The series of lines of the skin make an impression that can be reproduced by the ordinary line processes.  As in the case of spatter work, superfluous ink must be looked after before making the impression so as to avoid leaving hard edges.  Thumb markings lend themselves to the rendering of dark smoke, and the like, where the edges require to be soft and vague, and the free direction of the lines impart a feeling of movement.

Interesting effects of texture are sometimes introduced into pen drawings by obtaining the impression of a canvas grain.  To produce this, it is necessary that the drawing be made on fairly thin paper.  The modus operandi is as follows:  Place the drawing over a piece of mounted canvas of the desired coarseness of grain, and, holding it firmly, rub a lithographic crayon vigorously over the surface of the paper.  The grain of the canvas will be found to be clearly reproduced, and, as the crayon is absolutely black, the effect is capable of reproduction by the ordinary photographic processes.