Pigments, Paint and Painting: A practical book for practical men

by George Terry

The Chinaman has no knowledge whatever of chemistry, and of the principles of natural philosophy and statics generally his notions are of the most rudimentary and primitive description. How, then, in the face of these obvious disadvantages have the Chinese contrived to place themselves in the front rank amongst nations in the matter of certain chemical manufactures, one of the most important of which is the subject of this article—Vermilion?

We have seen with what ingenuity and pertinacity in carrying out his ends the Chinaman has succeeded in making perhaps the most delicate and perfect iron castings in the world. He has succeeded in that instance, not by any deep researches into the hidden mysteries of Nature, by no process of thought involving an enquiry into the “reason why”; to this the Chinaman is averse, the whole tendency of his education, such as it is, tends to make him satisfied with observing effects; it is sufficient to him to know that things are so, without going into troublesome or elaborate investigations into those changeless laws of Nature into which his philosophy teaches him that, as he cannot alter or control, research is fruitless: but that he has in his own small, ingenious, patient way observed effects to very good purpose, the unrivalled excellence of some of his manufactures testifies.

We will now enter a vermilion manufactory and watch the process from the first stage of mixing its two ingredients—mercury and sulphur—to the final process of weighing and packing this costly and beautiful pigment for the market.

The first objects to attract the visitor’s attention on entering the yard attached to the works will probably be large piles or stacks of charcoal, crates or baskets of broken crockery ware, and numerous rusty old iron pans of somewhat similar shape to rice pans, but considerably thicker and heavier. There will also probably be a few broken and disused cast-iron mortars. All these articles are the cast off or worn out implements of the manufacture, and will be described in their proper order.

On entering the factory proper, scores of little stone mills, each being turned by one man, and other long rows of workmen weighing out and wrapping up the vermilion, will be seen. The furnaces are then arrived at: there may be a score or more in number, and may be ten or twelve in each furnace room, five or six on each side. After passing these, the stores of quicksilver, sulphur, alum, glue, new spare iron pans, serviceable crockery ware, and sieves and other utensils used in the factory are arrived at, and this completes the view of the works.

The iron pans in which the vermilion is sublimed are those referred to above; they are circular and hemispherical in shape; all are of the same size and weight; they are cast upside down, and in the casting, a runner or lump of iron, two and three-eighths inches in diameter by from six-eighths to one inch in depth, is purposely left on every pan in order to enable the workman the more readily to handle the pan when stirring up its contents. The size of the pans proved by actual measurement to be 29¼ inches in diameter, by 8⅞ inches deep, and the weight 40 catties, or say about 53 lb.

These pans are set in rows of 5 or 6 on each side of a small rectangular room, in size some 12 feet by 15 feet; the door of this room is of wood and contains an aperture a few inches square in order to enable the workman to watch the progress of his operation, from time to time, without the necessity of lowering the temperature of the apartment by opening the door. The pans are set in brickwork, each pan having beneath it a grate to hold the charcoal used as fuel. There is no communication between the grates or furnaces under each pan, and no chimney, the flames and products of combustion finding exit from the front of the grate, which is left wholly open at all stages of the operation.

The process of manufacture is as follows:—Taking an iron pan which is of 4 inches smaller diameter than those described, and also in all other respects proportionally less, except the runner, which is of the same size, a skilled workman proceeds to weigh out 17⅓ lb. of sulphur. This he places in the pan, and adds about half the contents of a bottle of quicksilver. The pan with its contents is then put upon a small earthen brazier or portable furnace, the fuel used in which is charcoal. When the sulphur is sufficiently melted, the workman, taking an iron spatula or stirrer, rapidly stirs up the quicksilver with the sulphur, and gradually adds the remaining contents of the bottle of quicksilver, stirring the two ingredients together meanwhile until the mercury has wholly disappeared, or “been killed,” as the Chinese put it.

When this takes place, the pan is removed from the fire, a small quantity of water is added, and rapidly stirred up with the contents of the pan, which have now assumed a dark blood-red appearance and semi-crystalline structure. This mass is then turned out of the pan into an iron mortar, and then broken up into a coarse powder. This forms a charge for one of the large pans previously described, and when sufficient material has been prepared to charge all the pans in one furnace chamber the sublimation is proceeded with as follows:—

All the pans having received their quantum of crude vermilion, this is covered with a number of crockery-or porcelain-ware plates, of tough, strong manufacture, each about 8 inches in diameter; some of these plates, however, are broken up, and are in a more or less fragmentary condition. When these plates have been piled up into a dome-shaped heap of the same shape as the bottom of the upper pan, to which they should extend, the whole is covered with one of the smaller pans previously described.