nner could not be removed from place to
place. The old-fashioned panel work with its gold background was so
expensive that few artists could afford to paint pictures on the mere
chance of selling them. But the facilities and the economy of pure
tempera work, and work in oils, soon made easel pictures common.

Between the time of Giotto and that of Mantegna another means of
expression, besides painting, was found for artists, if not by accident,
by the ingenuity of the celebrated goldsmith, Maso Finiguerra, who was
the first man in Italy, and probably the first in the world, to take off
upon paper impressions in ink from an engraved plate.

[Illustration: THE PALATINE]

The especial branch of goldsmithing which he practised was what the
Italians still call 'niello' work, or the enamelling of designs upon
precious metals. The method of doing such work is this. Upon the piece
to be enamelled the design is first carefully drawn with a fine point,
precisely as in silver chiselling, and corrected till quite perfect in
all respects. This design is then cut into the metal with very sharp
tools, evenly, but not to a great depth. When completely cut, the
enamelling substance, which is generally sulphate of silver, is placed
upon the design in just sufficient quantities, and the whole piece of
work is then put into a furnace and heated to such a point that the
enamel melts and fills all the cuttings of the design, while the metal
itself remains uninjured. This is an easier matter than might be
supposed, because gold and silver, though soft under the chisel, will
not melt except at a very high temperature. When the enamel has cooled,
the whole surface is rubbed down to a perfect level, and the design
appears with sharp outlines in the polished metal.

Now anyone who has ever worked with a steel point on bright metal knows
how very hard it is to judge of the correctness of the drawing by merely
looking at it, because the light is reflected in all directions into
one's eyes, not only from untouched parts of the plate, but from the
freshly cut lines. The best way of testing the work is to blacken it
with some kind of colour that is free from acid, such as a mixture of
lampblack and oil, to rub the surface clean so as to leave the ink only
in the engraved lines, and then take an impression of the drawing upon
damp paper. That is practically what Finiguerra did, and in so doing he
discovered the art of engraving. Probably goldsmiths