This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
This is so much superior to our best methods of polishing that while the best European and American pianos are readily spoiled by atmospheric influences, Japanese lacquered wooden ware can resist boiling water. The following note gives a sketch of the process, and full details will be found in ' Workshop Receipts,' Third Series.
If the wood to be varnished be very porous, and the pores large enough to be visible to the naked eye, they are filled with a mixture of stone-powder and the lacquer called seshime, which is merely the sap of the branches of the varnish-tree, without any mixture. This paste of stone-powder and lacquer is put on with a wooden spatula, the workman taking good care to press hard on the spatula, so as to fill up all the pores, and to rub the varnish off the surface of the wood, which is kept as clean as possible. After the varnish is well hardened, the whole surface is polished with a soft stone - a kind of wedge-stone - so that the veins of the wood come out again. This filling process can be repeated, if necessary. Next, in order to give it a colour, the wood is painted over with a thin water-colour, or it is stained. When thus prepared, the object is then varnished with the lacquer shiunkei, of which a thin coating is put on with a brush, otherwise it would look too dark. On account of this lacquer taking its gloss in hardening, it requires a skilful person with a light hand to obtain a good result.
Only one coating is given.
In case the wood is close-grained and of even surface, the preliminary work will be unnecessary. The sheshine lacquer is alone used. It is rubbed into the wood with a ball of cotton, which is saturated with it. After it has been rubbed in, that which remains on the surface is taken off by rubbing with Japanese soft paper, so that in fact only a very thin layer remains.
It sometimes occurs that a Japanese lacquer is too thick, and will not spread evenly with a spatula, as occasionally happens when it is mixed with stone-powder. When this is the case, the Japanese workmen add powdered camphor to the varnish they are about to use. By this means it becomes more liquefied and flows much better.
There is another thing about the Japanese method of using this varnish that is worth knowing. The atmosphere in which it is to harden, after it has been applied, should be moist, and the room darkened. The Japanese lacquerers have in their work-rooms large boxes fixed against the walls. These are furnished with sliding-doors. The insides of these boxes are wetted with towels dipped in water; the lacquered ware is introduced, and the doors are closed. It generally requires 48 hours to harden the lacquer.