It is quite wonderful what a variety of different methods there are for making silver vases. We might here begin with the casting of silver, and then little by little get on to other subjects. There are three ways of melting silver so that it shall not burn.[117] In the first you use the bellows, constructing round their mouth a little brick furnace sufficient to quite cover the crucible, even to be some four fingers above it; then rub the crucible all over, inside and out, with olive oil; put the silver into it & place it on the furnace; you should not have too many coals aglow at first for fear of cracking the crucible, for that is apt to happen with the sudden heat, but let it get gradually hotter and hotter, without touching your bellows, until it is red hot. At this point you gently start blowing with the bellows. After a while you will see the silver beginning to float like water; then you strew a handful of tartar over it, and while it stays a moment so, take a piece of linen folded four or five times & well soaked in oil, to lay this over the crucible when you remove it from the coals. Then swiftly take hold of the crucible with your cramping tongs,[118] a pair of tongs made specially for catching hold of earthen crucibles, for if you catch hold of these as you would of iron crucibles you would break them, but these special tongs support the earthen crucible so that there is no danger of its breaking. Meanwhile, the moulds for pouring silver in must be at hand; these are made out of two iron plates of the requisite size and as occasion shall demand, and beneath[119] them place a few square rods about the size of your little finger, more or less, as the work may need. The plates are then bound together with stout iron clamps, struck with a hammer till they grip the moulds equally all round. Of these clamps you need six or eight according to the size of the mould. Then you paint round the junction of the moulds with liquid clay so as to prevent the silver from coming through.[120] When your moulds are well warmed, you pour a little oil into them, and stand them in an earthen pot of spent ashes, or even on the ground between four bricks, and so pour in your silver.[121] That is one of the methods of casting.
FOOTNOTES:
[117] Non si riarda.
[118] Imbracciatoie.
[119] ‘Infra’: should perhaps better be ‘between.’
[120] Per cagione che lo argento non versi.
[121] The sketch on [p. 79] may be taken as illustrative of the process.
CHAPTER XX. ANOTHER AND A BETTER WAY OF CASTING.
The Florentine gold-beaters used to have another way of casting, which was called casting in the mortar,[122] for so was the furnace called in which the casting was done. You take a number of bands of clean iron[123] about half a finger thick and as broad as a thumb, and weave them into a round shape, about one & one-third cubits high, sometimes smaller, sometimes larger than this in accordance with the quantity of the work you have to cast. It must be interlaced into a domed shape to about two-thirds of its circumference, and from the iron that remains over you make four legs on which the furnace is to stand. Note that where these legs commence you must make a grating, the openings of which are wide enough to allow of one finger and a half being put through them, this serves as a base for the furnace. And the furnace itself you construct by means of fashioning a cake of earth mixed with cloth shearings,[124] the kind of earth that glass-blowers use for their furnaces. Then you take a terra cotta tile and lay it on the base of your furnace, and strew a little ash over it. On this you stand your crucible filled with as much silver as it can hold, and set to work very carefully, much as you did in the previous method. You fill the furnace with coal, light it and leave it to get red by itself, for thus left, the draught will produce a tremendous fire, and you will cast better so than if you made fire with your bellows. I must warn you too, to make your crucibles out of clean iron, for earthenware ones would easily crack; this iron should however be coated over inside & out with a paste of clean ashes about half a finger in thickness, which must dry well before the silver is put in. Some take for this solution clay mixed with cloth parings, & the one is as good as the other. For the rest you proceed with your casting just as I showed you above.