Only one kind of tone should be used for brush drawing; it is laid on with the brush loaded with diluted color or ink. Chalk and pencil can make tone with broad, soft lines or by rubbing over the lines with the finger or stump. For ink drawing, one can make a wash of tone by brushing over the strokes with water, provided the ink previously used is water soluble. Sepia ink, once so popular, is water soluble; it comes from the ink bag of the cuttle fish. It is, however, notoriously sensitive to light, in contrast to modern materials which derive their coloring matter from pure carbon.
With the use of tone we are leaving the realm of pure line drawing. Tone increases the realism and plastic quality of the picture. Its use is a matter of choice, for it is impossible to say whether a tone drawing is "better" in principle than a line drawng, or vice versa.
Some forethought is necessary if tone is to be used. If one is working with insoluble, fast-drying ink, it does not matter whether the line drawing or the wash is done first; but if soluble watercolor is used, the wash would
dissoive and smudge what should remain as line drawing. Dark stroke accents cannot be put in until the end, and work must progress from soft lines and washes towards the dark values. This is always the correct mode of procedure for work on white paper, which, for this and other technical reasons is best for watercolor.
When working with pencil, chalk, or charcoal, it may be necessary to use the above-mentioned rubbing technique to - make a toned surface, although very soft strokes done one on top of the other or with a broad point will always give a sharper effect. If the rubbed tone is preceded by a finished and strongly formulated line drawing it provides the material for stumping. Working in this order it is easier to decide where tone will enhance the picture and where it is unnecessary.
Starting in the reverse order, with patches of tone which are afterwards defined with accents and contours, requires greater certainty, for there is no scaffold or framework from which to work towards the final idea. Whichever approach is used, tone or modeling must never show labor or anxiety. Its nature is to be flowing and easy, and it is better done with the fingers than with fine-pointed stumps, which carefully fill in every corner. Tone must show spontaneity. It is a very severe and impartial indicator of competence.