Another method of using a brush is hatching, the drawing of rows of parallel lines in either equal or varying thicknesses.  This method will lighten or darken a tone in varying degree, according to whether the lines are thick, thin, or gradated—­somewhat in the same way that lines of shading are drawn in line work.  In cases where the correction of intricate modelling is desired and where it would be very difficult to alter a part accurately by a deft stroke of the brush, this method is useful to employ.  A dry brush can be drawn across the lines to unite them with the rest of the work afterwards.  This method of painting has lately been much used by those artists who have attempted painting in separate, pure colours, after the so-called manner of Claude Monet, although so mechanical a method is seldom used by that master.

As your power of drawing increases (from the line drawing you have been doing), casts of hands and heads should be attempted in the same manner as has been described.  Illustrations are given of exercises of this description on pages 110 and 122.  Unfortunately the photographs, which were taken from the same study at different stages during the painting, are not all alike, the first painting of the lights being too darkly printed in some cases.  But they show how much can be expressed with the one tone, when variety is got by using the middle tone to paint into.  The two tones used are noted in the right-hand lower corner.

Try to train yourself to do these studies at one sitting.  But if you find you cannot manage this, use slower drying colours, say bone brown and zinc white, which will keep wet until the next day.

When you begin studying from the life, proceed in the same way with monochrome studies painted into a middle tone.

And what are you to do if you find, when you have finished, that it is all wrong?  I should advise you to let it dry, and then scumble a middle tone right over the whole thing, as you did at first, which will show the old work through, and you can then correct your drawing and proceed to paint the lights and shadows as before.  And if only a part of it is wrong, when it is quite dry rub a little, poppy oil thinned with turpentine over the work, as little as will serve to cover the surface.  If it is found difficult to get it to cover, breathe on the canvas, the slightest moisture will help it to bite.  When this is done, wipe it off with the palm of your hand or an old piece of clean linen.  Now paint a middle tone right over the part you wish to retouch, being careful about joining it up to the surrounding work, and proceed as before, drawing in the light and shadow masses.