glass are placed together, face
to face, the parallel lines ruled on them intersect each other at
right angles, giving a very fine "mosquito-netting" effect. The method
of making the negative is very similar to that described in making
line negatives, excepting that in making a half-tone negative the
screen is placed in the plate-holder directly in front of the
negative. The subject is then photographed, and the result is a
negative completely covered with a mass of fine transparent lines and
dots.

Copper is generally used instead of zinc in making half-tone plates.
In making a print on copper the light shines through the transparent
lines and dots of the negative and hardens the sensitized surface of
the plate. The black parts of the negative between the transparent
lines and dots protect the sensitized surface. When the plate, after
printing, is placed under a water tap, the parts of the sensitized
surface that have not been acted upon by light wash away, leaving a
print that becomes acid proof after being subjected to an intense
heat.

The method of etching a copper plate is similar to that already
described for etching zinc plates, excepting that sesquichloride of
iron is used instead of nitric acid. In a half-tone the dots and lines
are so close together that great depth is neither desirable nor
possible, and no steps are taken to prevent undercutting.

The half-tone plate, after it has been carried as far as possible by
mechanical processes, is capable of great improvement in the hands of
skilful engravers. The plate as it comes from the etching bath may be
termed a mechanical product. Though great skill is necessary in making
the negative, the print, and the etching, the hand-finishing gives the
plate many of its artistic qualities. The unfinished plate is apt to
be more or less "flat" in appearance; the high lights may not be light
enough, while the dark portions of the plate are apt, in cases, to be
too light. The most common methods of finishing are reetching and
burnishing. The finisher dips a camel's-hair brush in acid and
applies it to the high-light portions of the plate, or other places
that are too dark, and allows it to act on the metal until these parts
of the plate are lightened sufficiently. The parts of the plate that
are too light are made darker by rubbing down the surface of the plate
with a tool called the burnisher. The skilful, artistic finisher has
other methods at his command of making