§ 58. The Piece-Mould lined with a Skin of Wax.
Returning now to the pieces of the hollow mould, these are lined severally with yellow wax that has been softened and incorporated with a little turpentine and tallow.[[172]] When the wax is melted at the fire, it is poured into the two halves of the mould made up of the hollow pieces in such a manner as causes the wax to come thin according to the worker’s idea for the cast, and the pieces, which have been shaped to correspond with the relief of the core already made of clay, are joined to it and fitted and grafted together.
§ 59. This Skin of Wax applied over the Core.
Plate VII
ILLUSTRATION SHOWING PROCESS OF PIECE-MOULDING IN PLASTER
With thin skewers of copper the pieces of wax pierced with the said skewers are now fixed to the baked core, and so, piece by piece, they are inserted and fitted to the figure and render it entirely finished. This completed they proceed to remove all the superfluous wax that has overflowed into the interstices of the pieces, and bring it as well as possible to that finished excellence and perfection which one desires in the bronze cast. Before going further, the craftsman sets up the figure and considers diligently if the wax have any deficiency, and he proceeds to repair it and to fill up again, putting on more or taking away where necessary.[[173]]
§ 60. The fire-resisting Envelope applied over the Wax.
After that, the wax being completed and the figure braced together, he puts it where fire can be applied to it[[174]] on two andirons of wood, stone, or iron like a roast, arranging so that it can be raised or lowered; and with moistened ash, specially fitted for that purpose, by means of a paint brush he covers the entire figure so that the wax is quite concealed, and over every hollow and chink he clothes it well with this material. Having applied the ash to it he replaces the transverse rods, which pass through the wax and the core, just as he has left them in the figure, because these have to support the core within and the mould without, which is the casing of the hollow space between the core and the mould, where the bronze is to be poured. When this armature has been fixed, the artificer begins to take some fine earth, beaten together with horse dung and hair, as I said, and carefully lays a very thin coating all over which he allows to dry, and so on time after time with other coatings, always allowing each to dry until the figure becomes covered with earth raised to the thickness of half a span at the most.
§ 61. The External Armature.
This done, he girds those irons that hold the core within with other irons which hold the mould outside, and fixes them together, so that chained and bound the one to the other they form a mutual support,[[175]] the core within sustaining the mould without and the mould without holding firm the core within.