Scientific American 15, 1.1.1848
For the Scientific American.
(Continued from our last.)
Blue Japan Grounds.
Blue japan grounds may be formed of bright Prussian blue. The color may be mized with shellac varnish and brought to a polishing state by five or six coats of varnish of seedlac. This varnish, however, is apt to give a greenish tinge to the blue, as the varnish has a yellowish tinge and blue and yellow form green. Whenever a light blue is desired, the purest varnish must always be used.
Ground vermillion may be used for this, but being so glaring, it is not beautiful unless covered over with rose pink or lake, which have a good effect when thus used. For a very bright crimson ground, safflower or Indian lake should be used always dissolved in the alcohol of which the varnish is made. In place of this lake, carmine bay be used, as it is more common. The top coat of varnish must always be of the white seedlac - which was described in a former article - and as many coats given as will be thought proper - it is easy to judge of this.
If turmeric be dissolved in the spirit of wine and strained through a cloth and then mixed with pure seedlac varnish, it makes a good yellow japan. Saffron will answer for the same purpose in the same way, but the brightest yellow ground is made by a primary coat of pure chrome yellow, and coated successively with the varnish. Dutch puink is used for a kind of a cheap yellow japan ground. - If a little dragon's blood be added to the varnish for yellow japans, a most beautiful and rich salmon colored varnish is the result, and by these two mixtures all the shades of flesh colored japans are produced.
Green Japan grounds.
A good green may be made by mixing Prussian blue along with the chromate of lead, or with turmeric, or orpiment (sulphuret of arsenic) or ochre, only the two should be ground together and dissolved in alcohol and applied as a ground, then coated with four or five coats of shellac varnish, in the manner we have already described in a former article -
A very bright green is made by laying on a ground of Dutch metal, or leaf of gold and then coating it over with distilled verdigris dissolved in alcohol, then the varnishes on the top. This is a splendid green, brilliant and glowing.
Orange Colored Grounds.
Orange grounds may be made of yellow mixed with vermillion or carmine, just as a bright, or rather inferior color is wanted. - The yellow should always be in quantity to make a good full color, and the red added in proportion to the depth of shade. If there is not a good full body of yellow, the color will look watery, or bare as it is technically termed.
Purple Japan Grounds
This is made by a mixture of lake and Prussian blue, or carmine, or for an inferior color vermillion, and treated as the foregoing.
When the ground is laid on and perfectly dried, a fine coat of pure boiled nut oil then laid on and perfectly dried, is a good method to have a japan not liable to crack. But better plan is to use this oil in the varnish given - the first coat - after the ground is laid on, and which should contain considerable of pure turpentine. In every case where oil is used for any purpose for varnish, it is all the better if turpentine is mixed with it. Turpentine enables oils to mix with either alcohol or water. Alkalies have this property also.
(To be continued.)