According to Mr. Dickson, “the old way of making a cream enamel for stoving (a white was supposed to be impossible) was to mix ordinary tub white lead with the polishing copal varnish and to add a modicum of blue to neutralize the yellow tinge, stove same in about 170 deg.F. and then polish as before described”. “This,” continues Mr. Dickson, “would at the best produce but a very pale blue enamel or a cream. It was afterwards made with flake white or dry white lead ground in turps only and mixed with the polishing copal varnish with the addition of tints as required, by which means a white of any required character could be produced.”
Authorities state that these may be formed from bright Prussian blue or verditer glazed over with Prussian blue or of smalt. By bright Prussian blue possibly a genuine Prussian blue toned down to a sky blue with white lead is meant, and by verditer the variety known as refiners’ blue verditer, and as to smalt it must not be forgotten that it changes its colour in artificial light. Be that as it may, the pigment may be mixed with the shellac varnish according to the instructions already given, but as the shellac will somewhat injure the tone of the pigment by imparting a yellow tinge to it where a bright true blue is required, the directions already given as regards white grounds must be carried out.
Vermilion is the best pigment to use for a scarlet japan ground, and its effect will be greatly enhanced by glazing it over with carmine or fine lake. If, however, the highest degree of brightness be required the white varnish must be used. Vermilion must be stoved at a very gentle heat.
The basis of this japan ground is made up with madder lake ground in oil of turpentine, this constitutes the first ground; when this is perfectly dry a second coat of lake and white in copal varnish is applied, and the last coat is made up of lake in a mixture of copal varnish and turpentine varnish.
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.