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By heated air. By steam or hot-water pipes, coils of which circulate round the interior of the stove or under the floor. Such ovens may be either permanent, that is, built into masonry, or portable. Stoves heated by direct fire. These were, of course, the form in which japanning ovens were constructed somewhat after the style of a drying kiln.
In this method of japanning the higher the temperature is, the more rapidly does the drying take place; for instance, a thin layer of urushiol, or lacquer, hardens within 5 hours at 100° C., within 30 minutes at 150° C., and within 10 minutes at 180° C. Japanning at a high temperature with natural lacquer does not require the presence of the enzymic nitrogenous matter in the lacquer, and gives a transparent coating which is quite hard and resistant to chemical and mechanical action; in these respects it is distinguished from that dried at an ordinary temperature.
Be very careful in japanning, to grind your colours smooth in spirits of turpentine, then add a small quantity of turpentine and spirit varnish, lay it carefully on with a camel hair brush, and varnish it with brown or white varnish, according to the colour.
If the English process of japanning be more simple and produces a less durable, a less costly coating than the Japanese method, yet its practice is not so injurious to the health.
It is hardly necessary to state that all japanning or enamelling work must be done in a room or shop absolutely free from dust or dirt, and as far away as possible from any window or other opening leading to the open air, for two reasons one being that the draught therefrom may cool the oven or stove, and the other that the air may convey particles of dust into the enamelling shop.
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.
For japanning sheet-iron articles, which are really tin goods, such as tea-trays and similar things, first scour them well with a piece of sandstone, which will effectually remove all the scales and make the surface quite smooth. Then give the metal a coating of vegetable black, which must be mixed with super black japan varnish, thinned with turps, and well strained.
In japanning curved pieces, such as mud-guards, etc., in hanging up the work in the oven see that the liquid does not run to extremities and there form ugly blots or blotches of enamel. When white or other light tones are used for japanning they are mixed with japanners' varnish, and these require more careful heating in the oven or stove than darker tints or brown or black.
Before the expiration of his apprenticeship he had a shop of his own, and sold japanned tea-trays and bellows. When he was able to rent a house, he made all the furniture with his own hands, and took a pride in having it very good, either solid mahogany or veneered. He saved money in the japanning business, and then on these savings undertook to teach himself painting.
The great drawback to the use of gas for heating japanning and enamelling stoves is the great cost of coal gas. White Pigments. Barium sulphate and bismuth oxychloride. These two are used for the white lacquer or as a body for coloured lacquers.
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