heat increased too fast, either which error would make it blister, but
the slower the heat is increased and the longer it is continued,
provided it be restrained within a due degree, the harder will be the
coat of japan. This kind of japan requires no polish, having received
from the heat, when properly regulated, a sufficiently bright surface.


TORTOISE-SHELL GROUND.

This beautiful ground, produced by heat, is valued not only for its
hardness and its capacity to stand a heat greater than that of boiling
water, but also for its fine appearance. It is made by means of a
varnish prepared thus: Take one gallon of good linseed oil and half a
pound of umber, boil them together until the oil becomes very brown
and thick, strain it then through a coarse cloth and set it again to
boil, in which state it must be continued until it acquires a
consistency resembling that of pitch; it will then be fit for use.
Having thus prepared the varnish, clean well the surface which is to
be japanned; then apply vermilion ground in shellac varnish or with
drying oil, very thinly diluted with oil of turpentine, on the places
intended to imitate the more transparent parts of the tortoise-shell.
When the vermilion is dry, brush the whole over with the black varnish
thinned to the right consistency with oil of turpentine. When set and
firm put the work into a stove where it may undergo a very strong
heat, which must be continued a considerable time, for three weeks or
even a month so much the better. This ground may be decorated with
painting and gilding in the same way as any other varnished surface,
which had best be done after the ground has been hardened, but it is
well to give a second annealing at a very gentle heat after it has
been finished. A very good black japan may be made by mixing a little