Pigments Suitable for Japanning with Natural Lacquer And Examples of application
● White Pigments.
Barium sulphate and bismuth oxychloride.
These two are used for the white lacquer or as a body for coloured lacquers.
When the lacquer is to be dried at a high temperature barium sulphate is preferable, but when it is dried at an ordinary temperature bismuth oxychloride is better.
Since the lacquer is originally of a brown colour the white lacquer is not pure white, but rather greyish or yellowish.
Many white pigments, such as zinc oxide, zinc sulphide, calcium carbonate, barium carbonate, calcium sulphate, lead white, etc., turn brown to black, and no white lacquer can be obtained with them.
● Red Pigments.
Vermilion and red oxide of iron.
These two are used for the red lacquer, but vermilion should be stoved at a low temperature.
● Blue Pigment.—Prussian blue.
● Yellow Pigments.—Cadmium sulphide, lead chromate and orpiment.
● Green Pigment.—Chromium oxide (? Guignet's green).
● Black Pigment.—Lamp black. This is one of the pigments for black lacquer, but does not give a brilliant colour, therefore it is better to prepare the black lacquer by adding iron powder or some compound of iron to the lacquer.
Various mixed colours are obtained by mixing some of the above-mentioned pigments.
Examples of application are as follows:
(1) Golden Yellow.—Finished lacquer, 10 parts; gamboge, 1 to 3; solvent, 5. If utensils are lacquered with this thin lacquer and dried for about 2 hours in an air-oven at a temperature of 120° C. a beautiful hard coating of golden colour is obtained.
(2) Black.—Black lacquer, 10 parts; solvent 2 to 4. Utensils lacquered with this lacquer are dried for about an hour at 130° to 140° C.
(3) Red.—Vermilion, 10 parts; finished lacquer, 4; solvent, 2. This lacquer is dried for about an hour at 130° to 140° C.
(4) Khaki or Dirty Yellow.—Barium sulphate, 100 parts; chromic oxide, 3; finished lacquer, 20 to 25; solvent, 15. This lacquer is dried for about half an hour at 160° C.
(5) Green.—Barium sulphate, 100 parts; chromic oxide, 20 to 50; finished lacquer, 40 to 50; solvent, 20. This is dried for about 10 minutes at 160° C.
(6) Yellow.—Barium sulphate, 100 parts; lead chromate, 40; finished lacquer, 40; solvent, 20. This is dried for about 15 minutes at 150° C.
Almost all pigments other than the above-mentioned are blackened by contact with lacquer or suspend its drying quality.
Several organic lakes can be used for coloured lacquers, that is to say, Indian yellow, thioflavin, and auramine lake for a yellow lacquer; fuchsine, rhodamine, and chloranisidin lake for a red; diamond sky blue, and patent nileblue lake for a blue; acid green, diamond green, brilliant milling green, vert-methyl lake, etc., for a green; methyl violet, acid violet, and magenta lake for a violet; phloxine lake for a pink.
These lakes, however, are decomposed more or less on heating and fail to give proper colours when dried at a high temperature.
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