Wire Drawing
as described in
The Pirotechnia of Vannoccio Biringuccio
The Classic Sixteenth-Century Treatise on Metals and Metallurgy

Gnudi, Martha Teach & Smith, Cyril Stanley. The Pirotechnia of Vannoccio Biringuccio : The Classic Sixteenth-Century Treatise on Metals and Metallurgy. Dover Publications, Inc.: New York 1990. ISBN 0-486-26134-4 pages 377-381

THE EIGHTH CHAPTER

Concerning the Practice of Making Gold into Wire and also Silver, Iron, Copper, and Brass.

I am sure you know that it is necessary to draw the gold into wire in order to make gold cloth, gold embroidery, or gold filigree work. Just as it is beaten to form leaf for ornamenting pictures, so also can gold be drawn easily. The same is done with silver and tin, and I believe it could also be done with iron, copper, and brass. Although brass is not so soft as the others, it is seen to spread out and become thin by much hammering, and, because it has a shadow of resemblance to the color of gold, those thin and resonant leaves are made from it that are commonly called tinsel.

In short, wire is drawn of every metal, excepting tin and lead, because of the need of strong bindings which must enter the fire while bound. It can be made in any thinness and length that the craftsman wishes, especially that which is made of gold and silver and which is so long and thin that it is woven into cloth for dresses just like linen and wool, and is embroidered in the company of silk with no distinction.

Goldsmiths also draw gold into wire to make the ornamentation of their works easy and more attractive. These works, brought together and soldered well, are those which are commonly called filigree, whether they be of silver or gold. Brass and steel, which [139v] are stronger things, are also drawn into wires to make strings for musical instruments, as fine or as thick as pleases the one who uses them. To sum up, I do not know that there is in all this work anything notable but a certain experience and great patience.

In this, two procedures are followed. One is drawing with a heavy capstan with a windlass, and the other is with a little drum worked by hand, after having first reduced the bar under the hammer as round and as long as possible. Then it must be annealed and, when annealed, it is usually taken to a small horizontal windlass fitted into a frame, or to [a machine] with the force of a screw, or else a large windlass pivoted vertically. On any of these or other drawing machines the steel drawplates are arranged in firmly fixed blocks of wood. The plates are a half palmo long with several rows of holes of successive sizes. In addition, a pair of large tongs with flat, serrated mouths and open legs are needed. These should be held by a stirrup-shaped iron ring which has a hook at the foot to which is attached the end of a belt or rope, the rest of which is wrapped around the small windlass or the large one by turning. In this way the tongs close when you pull them and in that instant take hold of the tip of the ends of the gold or silver wire, which has been well greased with new wax and put by the craftsman into one of those holes of the drawplate. Then by turning the levers of these instruments with the force of men, the little bars of the said metals are pulled and caused to pass through all the holes of the drawplate one by one.

Since the large instruments do not serve well when the wire has been reduced to a certain point, two drums are pivoted horizontally on a bench and the drawplate is fixed between these two, with little holes of successive sizes so as to make the wire ever finer. By turning one of these drums the desired quantity of wire is wound, passed though the drawplate, and attached to the other roller. The plate is reversed and the wire put in another hole. Thus, from one hole to another, turning now one drum and now the other, the wire is made to become very fine, always

pyrotechnia1.jpg (43245 bytes)
Figure 72. Wire Drawing with capstan, windlass, and drums
(click on image to enlarge)

keeping it properly taut so that it may not tangle. When it has been made thus, it is put on other spools. Remember that while you are working it you must always keep it greased with new wax, for besides easing its passage through the holes, this also keeps its color yellow and beautiful.

Finally, in my opinion, this art consists of two things. One is in preparing the drawplates well so that their holes may be kept round. They should be of good and very fine steel. The other is that the gold and silver that you wish to draw be fine, of a soft nature, and that it be kept well annealed to the degree where it can be put on the drum by hand at the start. This method is also followed in drawing every other metal, that is, steel, brass, iron, and copper, but I shall tell you more of iron in detail farther on.

[140] Concerning this drawing of gold and silver I wish to tell you how it is customary to proceed today in almost all works in order to effect a saving of the quantity of gold that would enter the materials that are woven, or in order to alter it for fraud. This wire is also fabricated so that it appears to be all fine gold and actually is almost all silver, for the weight of only one ducat of fine gold is put in every pound; and some, desirous of greater fraud, make the core not even of fine silver but of copper, and gild it. Briefly, to do this a cast bar of copper or fine silver is made, then beaten and made round by the hammer. It should be three-quarters of a braccio long or less. After being well filed and cleaned, a covering of fine hammered gold is soldered over it (or if it is copper you can make this covering

pyrotechnia2.jpg (50476 bytes)
Figure 73. Drawing heavy wire by means of water power
(click on image to enlarge)

of silver) in that quantity by weight that you wish to put on. Solder it on a little furnace with charcoal and with flames of elder, almost bringing it to a melt before rubbing it with a dry stick, as is customary, or with chalcedony or bloodstone so that the applied covering may spread out all over it and everywhere come in contact with the thing with which it is to be soldered. Then it is cooled, annealed again, hammered thin, and it is ready to be put in the drawplate so that you may proceed as I told you above. Certainly if it is not done for fraud, this process is a beautiful thing in this art and worthy of great consideration, especially since the gold that is applied thins out over the thing to which it is soldered and never reveals it on the outside. The wire may be drawn out so fine that the eye can scarcely perceive it, yet it is always very well gilded all over.

This is all concerning the making of wire in which gold or silver is involved, and that of all the others except heavy iron is included in the one demonstrated here. For iron a water-wheel mechanism is built. At the end of a journal there is a bent iron with a ring that has a hook to which a band is attached with a slip knot. A short distance away a block of wood with the drawplate is fixed in the ground. Between the block and the wheel a pit is made in the ground to the depth of a manís knee. The operator stands in this pit with a pair of [140v] large tongs with an iron stirrup, attached to the band, which holds the legs of the tongs so that they close when it is pulled and open when it is released. Letting the water run the wheel, the man, who has tied the band in the middle of the bent axle, lets himself be drawn backwards and then pushes forward. His only care is to seize with the jaws of the tongs the end of the wire that issues from the drawplate with every return that he makes. He sits in the said pit on a board attached at the ends to a beam with two long irons which hold him swinging, so that he moves back and forth as the wheel pushes or pulls and can take hold with the tongs. With this construction iron can be drawn out to any desired length and thickness, if it is annealed often, and also gold, silver, and copper.

In addition to this method, I have seen iron drawn out without a water-wheel mechanism. This other way used horizontal drums, as I told you is done with gold, but for this it is necessary to have the iron very greatly thinned and well annealed. The same could be done with a large wheel for turning it, and if one did not have water it could be done with the motion of a reel or with a horse or man who could move it by walking inside, or with counterweights or other levers that have force. Let what has been told you of this art suffice.

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