necessary, a
priming or undercoat is employed. It is customary to fill up any
uneven surface, any minute holes or pores, and to render the surface
to be japanned uniformly smooth. But such an undercoat or priming is
not always applied, the coloured varnish or a proper japan ground
being applied directly on the surface to be japanned. Formerly this
surface usually, if not always, received a priming coat, and it does
so still where the surface is coarse, uneven, rough, and porous. But
where the surface is impervious and smooth, as in the case of metallic
surfaces, a priming coat is not applied. It is also unnecessary to
apply such a coat in the case of smooth, compact, grained wood. The
reason for using this coating is that it effects a considerable saving
in the quantity of varnish used, and because the matter of which the
priming is composed renders the surface of the body to be varnished
uniform, and fills up all pores, cracks, and other inequalities, and
by its use it is easy after rubbing and water polishing to produce an
even surface on which to apply the varnish. The previous application
of this undercoat was thus an advantage in the case of coarse, uneven
surfaces that it formed a first and sort of obligatory initial stage
in the process of japanning. This initial coating is still applied in
many instances. But it has its drawbacks, and these drawbacks are
incidental to the nature of the priming coat which consists of size
and whiting. The coats or layers of japan proper, that is of varnish
and pigment applied over such a priming coat, will be continually
liable to crack or peel off with any violent shock, and will not last
nearly so long as articles japanned with the same materials and
altogether in the same way but without the undercoat. This defect may
be readily perceived by comparing goods that have been in use for some
time in the japanning of which an undercoat has been applied with
similar goods in which no such previous coat has been given. Provided
a good japan varnish and appropriate pigments have been used and the
japanning well executed, the coats of japan applied without a priming
never peel or crack or are in any way damaged except by violence or
shock, or that caused by continual ordinary wear and tear caused by
such constant rubbing as will wear away the surface of the japan. But
japan coats applied with a priming coat crack and fly off in flakes at
the slightest concussion, at any knock or fall, m