Plate VIII
ENGRAVINGS ILLUSTRATING THE PROCESS OF CASTING IN BRONZE
From the French Encyclopédie
§ 67. A simpler Method of Casting small Figures and Reliefs.
Now should the artificer wish to cast small figures in metal, they are first made of wax, or if he happen to have them in clay or other material, he makes the shell of plaster over them in the same way as for the large figures, and fills it all with wax. But the shell must be moistened that the wax, when poured into it, may set (with a hard skin) by reason of the coldness of the wet cast. Then by shaking about and agitating the cast, the wax (which is not hardened) within the cavity is thrown out, so that the cast remains hollow in the interior: the craftsman afterwards fills up the vacant space with clay and puts in skewers of iron. This clay serves then for core, but it must be allowed to dry well. Thereafter he adjusts the mould as for the other large figures, giving it its armature and placing the tubes for the vents. Then he bakes it and gets rid of the (skin of) wax and thus the vacant space remains clear so that the bronze can easily be poured in. The same is done with the low and half reliefs and with every other work in metal.
§ 68. Chasing the Cast and Colouring the Bronze.
These casts being finished, the workman then, with suitable tools, that is, with burins, burnishers, chasing tools, punches, chisels and files, removes material where needed, and where needed presses inward the overflow of the metal and smoothes it down; and with other tools that scrape, he shaves and cleans the whole of it diligently, and finally with pumice stone gives the last polish. This bronze which is red when it is worked assumes through time by a natural change a colour that draws towards black. Some turn it black with oil, others with vinegar make it green, and others with varnish give it the colour of black, so that every one makes it come as he likes best.
§ 69. Modern Tours de Force in small Castings.
But that is a truly marvellous thing which is come to pass in our times, this mode of casting figures, large as well as small, so excellently that many masters make them come out in the cast quite clear so that they have not to be chased with tools, and as thin as the back of a knife. And what is more, some clays and ashes used for this purpose are actually so fine, that tufts of rue and any other slender herb or flower can be cast in silver and in gold, quite easily and with such success, that they are as beautiful as the natural; from which it is seen that this art is more excellent now than it was in the time of the ancients.
CHAPTER V. (XII.)
Concerning Steel Dies for making Medals of bronze or other metals and how the latter are formed from these metals and from Oriental Stones and Cameos.