.

18. =Smoking.=--Without waiting for the plate to cool, I turn it over,
and present its varnished side to the smoke of a torch or a wax taper,
which I hold at a distance of about two centimetres from the plate, so
as not to injure the varnish. I keep moving the flame about in all
directions, to avoid burning the varnish (which latter would take place
if the flame remained too long at the same point), and thus I obtain a
brilliant black surface. All the transparency is gone; we see neither
copper nor varnish, and this is a sign that our operation has succeeded.
All we need do now is to allow the plate to cool and the varnish to
harden, and then you can commence making your drawing.

You call my attention to the fact that the varnish, in cooling, loses
the brilliancy which it had in its liquid state. This is always the
case. And see the perfect neatness and evenness of the varnished and
smoked surface! Here is a plate which was spoiled in the smoking. The
first thing that strikes us is that we see the marks left by the passage
of the taper. At a pinch, these marks might, perhaps, be no
inconvenience to us in working; but here the brilliant black is broken
by very dull spots. These are places in which the varnish was burned;
it will scale off under the needle, and has lost the power of resisting
the acid. We must therefore clean this plate with spirits of turpentine,
and commence operations afresh.

The ground is blackened, because its natural transparency does not
permit us to see the work of the point. This work produces what might be
called a negative design; that is to say, a design in bright lines on a
black ground. This is rather perplexing at first, but you will soon
become accustomed to it.

C. DRAWING ON THE PLATE WITH THE NEEDLE.

19. =The Transparent Screen.=--You must place yourself so as to face
this window, and between you and it we must introduce, in an inclined
position, a transparent screen made of tracing paper stretched on a
wooden frame, which will prevent your seeing the window. This screen
will soften and strain the light; it will reduce the reflection of the
copper, and will allow you to see what you are doing.

In designing on the plate out of doors, the screen is unnecessary,
since, as the light falls equally upon the copper from all directions,
the reflection is done away with, and the copper does not dazzle the eye
as it does when the light emanates from a single source.

20. =Needles