Japanese Process of Varnishing.

Manufacturer and builder 10, 1878

In 1873 Professor Rein, of Marburg, was sent by the Prussian Minister of Finance and Commerce to Japan, to study those branches of industry in whirls that people excel, and thoroughly examine processes of manufacture. Upon his return be gave a course of instruction in varnishing or japanning, to an employé of Messrs. Beuttemeueller & Co., from whose report to the Baden Minister of Commerce we abstract the following:

The course of lessons given by Dr. Rein lasted nine hours a day for six days. Dr. Rein filled up the intervals, while waiting for the work to dry, with theoretical instructions about the plants from which the varnishes are prepared, the method of preparing the different qualities, etc.

Japanese varnish is obtained from a tree, Rhus Vernicifera. This varnish tree, which is called Urishi naki by the Japanese, reaches a hight of 33 feet; and at the age of 40 years, the trunk is 40 inches its circumference, grows very slowly — about 13 inches per year. The wood is strong and heavy, has few branches, consequently very little foliage, and the tree is not very pleasing to the eye. The fruit resembles grapes, and grows in thick spikes on the branches. In October the fruit is ripe, and is collected in November to obtain from it a vegetable wax, known as Japanese wax. The tree is best propagated from the root shoots. It reaches its greatest perfection at its 18th year, and then produces the largest yield of lac or varnish. This is obtained by slitting the bark in a horizontal direction, and may be performed at any time between April and October; later in the year the lac is very thick and viscid, so that its collection is attended with much greater difficulty. The lac tapper carries his own peculiar bow-shaped knife, made for this purpose, with which he cuts a 2-millimeter slit in the trunk of the tree in a horizontal direction, and then draws the point of the knife threugh the cut again, to remove any chips formed by the first cut. This cut is made low down; on the opposite side of the trunk 13 or 20 cm. (6 or 8 inches) farther up, a second cut is made, then on this side again, and so on until the trunk has 6 or 10 such cuts. After he has cut 10 or 15 trees, he returns to the first tree and collects the sap oozing from the cuts, which sap is light gray, and thick; but by exposure to the air, it at once turns dark brown and afterward quite black. The crude lac is called Ki-urushi.

The tree is hacked in this way for 60 to 80 days, until it dies; it is then cut down, the wood chopped up and put in hot water, which extracts the last remnant of the sap. From the tree when cut down ¼ liter at moat of sap is obtained, and this forms the poorest kind of lac. The value of one hundred lac trees is about thirty to forty dollars.

The lac is purified in the following manner: It is first filtered through cotton stuff, ground on a paint stone like ordinary paints, mixed with water, and the water evaporated again by warming. The finer sorts are bleached in shallow dishes in the sun. The best kind is called Nashyi-urushi, the poorer kind Henki-urushi, the unbleached Jeshime-urushi. The black varnish, Roiro-urushi, is made from the crude lac, Ki-urushi. There are about 20 different kinds in the market, of which the above named are must used. The cost in Japan is; Nashyi-urushi $4.77 per lb.; Jashime-urushi, $1,65 per lb; Roiro-urushi $3.70 per lb. The Japanese varnishes are as often adulterated in the trade as wine in Germany (or milk with us).

The operation of varnishing is conducted totally different from whet it is in Europe. The Japanese apply their varnishes mostly to wood-work, less frequently to copper and unglazed stoneware and porcelain. When applied directly to tinware, the japan does not stick. The varnishes, when applied, are generally a brilliant black, dark colored, impure vermilion, or impure dark green, or dark gray. Pure light colors and white cannot be produced with Japan varnish.

The Japanese varnishers prepare their woodenware with the utmost care, the surfaces are smoothed and the chinks filled with cement. The ground coat is a mixture of Jeshime-urushi with paste; upon this is laid Japanese paper, rubbed smooth with a brush, and dried. Afterwards several very thin coats of the same varnish, now and then well dried, and after every coat, polished with Japanese carbon.

The drying is performed in is moist atmosphere. For this purpose they take a box that will shut tightly, sett the article to be dried in it, close the box and wet it on all sides with water. After 24 hours one coat is dried. If the article is to be black, it in now given a coat of black varnish, Roiro-urushi, but if it is to be gray or gray-brown, Jeshime-urushi is used instead, and if it is to be red, the latter varnish is mixed with vermilion. The appearances of gold and pearl are obtained by mixing real gold dust, or mother-of-pearl dust, with the varnish, whereby a beautiful effect is produced. It is then dried, rubbed down, and polished; and if there are gold, tortoise-shell, or mother-of-pearl decorations, another coat of azure varnish, Nashyi-urushi, is applied. Dr. Rein communicated other methods of japanning, the introduction of which in this place would lead us too far.

In applying their varnishes, the Japanese use broad brushes, the brietles of which are very stiff, and inserted in wood, just as the graphite is in our lead pencils. After long use the bristles get worn short, and the wood is cut away as in sharpening a pencil, exposing more of the bristles. A very fine piece of work receives 18 coats; these never fade with time, but rather improve, bear a high heat, and are totally unaffected by acids, spirits, and the like.

Notwithstanding it is not likely that the details of this process will be imitated here, on account of the labor required, and the want of the same materials used in Japan, it may be well for those prosecuting this business to receive the above information, as from it they relay obtain some useful hints.

Ei kommentteja :