soft, it must be smoked. Light your tapers or your oil torch, and turn
the plate upside down. Allow the flame just to touch the plate, and keep
moving it about rapidly, so that it may touch all points of the
plate, without remaining long at any one of them. If this precaution is
ignored, the ground will be burned, with the result before stated. The
smoking is finished as soon as the plate is uniformly blackened all
over, and the glimmer of the metal can no longer be seen through the
ground. Now allow the plate to cool so that the ground may harden.
_Avoid dust as much as possible_ while grounding and smoking the plate.
Particles of dust embedded in the ground may cause holes which will
admit the acid where you do not wish it to act.

5. =Points or Needles.=--The plate is now ready for drawing upon it, but
before you can proceed to draw you must prepare your points or needles.
Two will do for this first experiment, a fine one and a coarse one. For
the fine one you may use a sewing-needle, for the coarser one a medium
embroidery needle, both set in wood so that the points project about a
quarter of an inch. If you are going to use rat-tail files, grind the
handle-ends on your oil-stone until they attain the requisite fineness.
Hold the file flat on the stone, so as to get a gradually tapering
point, and turn continually. See to it that even the point of your
finest needle is not too sharp. If it scratches when you draw it lightly
over a piece of card-board, describe circles with it on the board until
it simply makes a mark without scratching. The coarse needle must be
evenly rounded, as otherwise it may have a cutting point somewhere.

[Illustration: Plate A.]

6. =Drawing on the Plate.=--As the purpose of your experiment is simply
to familiarize yourself with the _technicalities_ of etching, that is to
say, with the preparation of the plate, the management of the points,
and the action of the acid, it will be well to confine yourself to the
drawing of lines something like those on Pl. A. It is the office of the
point simply to _remove_ the ground, and _lay bare the copper_. But this
it must do thoroughly, for the slightest covering left on the plate will
prevent the acid from attacking the copper. You must therefore use
sufficient pressure to accomplish this end, but at the same time you
must avoid cutting into the copper by using too much pressure. Wherever
the point has cut the copper the acid acts more rapidly, as t