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Page 5
BRIGHT PALE YELLOW GROUNDS.
Orpiment or King's yellow may be used, and the effect is enhanced by
dissolving powdered turmeric root in the methylated spirits from which
the upper or polishing coat is made, which methylated spirits must be
strained from off the dregs before the seed-lac is added to it to form
the varnish. The seed-lac varnish is not so injurious to yellow
pigments as it is to the tone of some other pigments, because, being
tinged a reddish yellow, it does little more than intensify or deepen
the tone of the pigment.
GREEN JAPAN GROUNDS.
Green japan grounds are produced by mixing Prussian blue or distilled
verdigris with orpiment, and the effect is said to be extremely
brilliant by applying them on a ground of leaf gold. Any of them may
be used with good seed-lac varnish, for reasons already given. Equal
parts by weight of rosin, precipitated rosinate of copper, and
coal-tar solvent naphtha will give a varnish which, when suitably
thinned and the coats stoved at a heat below 212� F., will give a
green japan second to none as a finishing coat as regards purity of
tone at least. To harden it and render it more elastic half of the
rosin might be replaced by equal weights of a copal soluble in solvent
naphtha and boiled linseed oil, so that the mixture would stand thus:
rosinate of copper 1 lb., rosin 1/2 lb., boiled oil 1/4 lb., hard
resin (copal) 1/4 lb., solvent naphtha 1 lb. When heated to a high
temperature this rosinate of copper varnish yields a magnificent ruby
bronze coloration, especially on glass. Verdigris dissolves in
turpentine, and successful attempts might be made to make a green
japan varnish from it on the lines indicated for rosinate of copper.
ORANGE-COLOURED GROUNDS.
Orange-coloured grounds may be formed by mixing vermilion or red lead
with King's yellow, or orange lake or red orpiment (? realgar) will
make a brighter orange ground than can be produced by any mixture.
PURPLE GROUNDS.
Purple grounds may be produced by the admixture of lake or vermilion
with Prussian blue. They may be treated as the other coloured grounds
as regards the varnish vehicle.
BLACK GROUNDS.
Black grounds may be formed either from lamp black or ivory black, but
ivory black is preferable to lamp black, and possibly carbon black or
gas black to either. These may be always applied with the shellac
varnish as a vehicle, and their upper or polishing coats may consist
of common seed-lac varnish. But the best quality of ivory black ground
in the best super black japan yields, after suitable stoving, a very
excellent black indeed, the purity of tone of which may be improved by
adding a little blue in the grinding.
COMMON BLACK JAPAN GROUNDS ON METAL.
Common black japan grounds on metal by means of heat are procured in
the following manner: The surface to be japanned must be coated over
with drying oil, and when it is moderately dry must be put into a
stove of such heat as will change the oil black without burning it.
The stove should not be too hot when the oil is put into it nor the
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
japan gold size with ivory or lamp-black, this will develop a good
gloss without requiring to be varnished afterwards.
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