This section is from the "The elements of drawing & the elements of perspective" book, by J. M. Dent & Sons. Also see Amazon: The Elements Of Drawing & The Elements Of Perspective.
As soon as you can copy every curve slowly and accurately, you have made satisfactory progress; but you will find the difficulty is in the slowness. It is easy to draw what appears to be a good line with a sweep of the hand, or with what is called freedom1; What is usually so much sought after under the term freedom is the character of the drawing of a great master in a hurry, whose hand is so thoroughly disciplined, that when pressed for time he can let it fly as it will, and it will not go far wrong. But the hand of a great master at real work is never free: its swiftest dash is under perfect government. Paul Veronese or Tintoret could pause within a hair's breadth of any appointed mark, in their fastest touches; and follow, within a hair's breadth, the previously intended curve. You must never, therefore, aim at freedom. It is not required of your drawing that it should be free, but that it should be right: in time you will be able to do right easily, and then your work the real difficulty and masterliness is in never letting the hand be free, but keeping it under entire control at every part of the line.
Meantime, you are always to be going on with your shaded squares, and chiefly with these, the outline Exercises being taken up only for rest.
As soon as you find you have some command of the pen as a shading instrument, and can lay a pale or dark tint as you choose, try to produce gradated spaces like Fig. 2., the dark tint passing gradually into the lighter ones. Nearly all expression of form, in drawing, depends on your power of gradating delicately; and the gradation is always most skilful which passes from one tint into another very little paler. Draw, therefore, two parallel lines for limits to your work, as in Fig. 2., and try to gradate the will be free in the best sense; but there is no merit in doing wrong easily.
These remarks, however, do not apply to the lines used in shading, which, it will be remembered, are to be made as quickly as possible. The reason of this is, that the quicker a line is drawn, the lighter it is at the ends, and therefore the more easily joined with other lines, and concealed by them; the object in perfect shading being to conceal the lines as much as possible.
And observe, in this Exercise, the object is more to get firmness of hand than accuracy of eye for outline; for there are no outlines in Nature, and the ordinary student is sure to draw them falsely if he draws them at all. Do not, therefore, be discouraged if you find mistakes continue to occur in your outlines; be content at present if you find your hand gaining command over the curves.Shade evenly from white to black, passing over the greatest possible distance, yet so that every part of the band may have visible change in it. The perception of gradation is very deficient in all beginners (not to say, in many artists), and you will probably, for some time, think your gradation skilful enough, when it is quite patchy and imperfect. By getting a piece of grey shaded riband, and comparing it with your drawing, you may arrive, in early stages of your work, at a wholesome dissatisfaction with it.
Widen your band little by little as you get more skilful, so as to give the gradation more lateral space, and accustom yourself at the same time to look for gradated spaces in Nature. The sky is the largest and the most beautiful; watch it at twilight, after the sun is down, and try to consider each pane of glass in the window you look through as a piece of paper coloured blue, or grey, or purple, as it happens to be, and observe how quietly and continuously the gradation extends over the space in the window, of one or two feet square. Observe the shades on the outside and inside of a common white cup or bowl, which make it look round and hollow1; and then on folds of white drapery; and thus gradually you will be led to observe the more subtle transitions of the light as it increases or declines on flat surfaces. At last, when your eye gets keen and true, you will see gradation on everything in Nature.
But it will not be in your power yet awhile to draw from any objects in which the gradations are varied and complicated; nor will it be a bad omen for your future progress, and for the use that art is to be made of by you, if the first thing at which you aim should be a little bit of sky. So take any narrow space of evening sky, that you can usually see, between the boughs of a tree, or between two chimneys, or through the corner of a pane.If you can get any pieces of dead white porcelain, not glazed, they will be useful models.Window you like best to sit at, and try to gradate a little space of white paper as evenly as that is gradated - as tenderly you cannot gradate it without colour, no, nor with colour either; but you may do it as evenly; or, if you get impatient with your spots and lines of ink, when you look at the beauty of the sky, the sense you will have gained of that beauty is something to be thankful for. But you ought not to be impatient with your pen and ink; for all great painters, however delicate their perception of colour, are fond of the peculiar effect of light which may be got in a pen-and-ink sketch, and in a woodcut, by the gleaming of the white paper between the black lines; and if you cannot gradate well with pure black lines, you will never gradate well with pale ones.