e; and sometimes a skillfully rased piece of paper will, in the
midst of transparent tints, answer nearly the purpose of chalky
body-color in representing the surfaces of rocks or building. But
artifices of this kind are always treacherous in a tyro's hands,
tempting him to trust in them: and you had better always work on white
or gray paper as smooth as silk;[43] and never disturb the surface of
your color or paper, except finally to scratch out the very highest
lights if you are using transparent colors.

162. I have said above that body-color drawing will teach you the use of
color better than working with merely transparent tints; but this is not
because the process is an easier one, but because it is a more complete
one, and also because it involves some working with transparent tints in
the best way. You are not to think that because you use body-color you
may make any kind of mess that you like, and yet get out of it. But you
are to avail yourself of the characters of your material, which enable
you most nearly to imitate the processes of Nature. Thus, suppose you
have a red rocky cliff to sketch, with blue clouds floating over it. You
paint your cliff first firmly, then take your blue, mixing it to such a
tint (and here is a great part of the skill needed) that when it is laid
over the red, in the thickness required for the effect of the mist, the
warm rock-color showing through the blue cloud-color, may bring it to
exactly the hue you want (your upper tint, therefore, must be mixed
colder than you want it); then you lay it on, varying it as you strike
it, getting the forms of the mist at once, and, if it be rightly done,
with exquisite quality of color, from the warm tint's showing through
and between the particles of the other. When it is dry, you may add a
little color to retouch the edges where they want shape, or heighten the
lights where they want roundness, or put another tone over the whole:
but you can take none away. If you touch or disturb the surface, or by
any untoward accident mix the under and upper colors together, all is
lost irrecoverably. Begin your drawing from the ground again if you
like, or throw it into the fire if you like. But do not waste time in
trying to mend it.[44]

163. This discussion of the relative merits of transparent and opaque
color has, however, led us a little beyond the point where we should
have begun; we must go back to our palette, if you please. Get a cake of
each o