Metallic threads, or fine rods, produced by forcibly drawing the ductile metals through a hole of less area than their previous transverse sections. The sizes of which wire are made are from three-eighths of an inch in diameter to that of the four-thousandth part of an inch. For the purposes of embroidery and similar work, gold and silver are commonly drawn to such fineness as to be flexible, and as conveniently wrought with a needle, as the filaments of silk, flax, etc. with which they are usually mixed. See the articles Gold and Silver.
The earliest attempt to draw ductile metal into threads, by forcing them through holes in a steel plate, does not appear to be determined. At first, wire was formed entirely by the hammer; and this process of art soon became a distinct trade. Beckman observes, "As long as the work was performed by the hammer, the artists at Nuremberg were called wire-smiths, but after the invention of drawing iron, they were called wire-drawers, or wire-millers. Both these appellations occur in the history of Augsburg, so early as the year 1351, and in that of Nuremberg, in 1360; so that, according to the best information I have been enabled to obtain, I must class the invention of the drawing-iron, or proper wire-drawing, among those of the fourteenth century." About two hundred years, however, elapsed before the art was introduced into this country; nevertheless, the skill of our native artists soon enabled them to surpass the foreign manufacture, if any reliance can be placed in the statement contained in a proclamation of King Charles I. in 1630, wherein it is set forth, "That iron-wire is a manufacture long practised in the realm, whereby many thousands of our subjects have long been employed; and that English wire, of the toughest and best Osmond iron, a native commodity of this kingdom, and is much better than what comes from foreign parts, especially for making wool-cards, without which no good cloth can be made."
For the manufacture of wire for piano-fortes and other musical instruments, Berlin has long been celebrated; and it still deserves a preference for these purposes, in the opinion of many of our artists.
For making iron wire, none but the very best and toughest iron should be used; that made entirely from charcoal and of the Cumberland ore having the preference Formerly the bars were reduced to the required sizes for the wire-drawer by tilting it; but now we understand the manufacturers roll the bars down through small grooved rolls to very small sizes, and thus materially save the labour of drawing. The rolls for this purpose are the same as described in the article Iron (which see,) but are superiorly finished, and fitted up with great accuracy of adjustment, so as to roll very perfect cylinders of wire down to an eighth of an inch in diameter. The rollers are generally from seven to eight inches in diameter, and make upwards of 300 revolutions per minute; so that the rapidity with which this rolled or "black wire," (as it is sometimes called, to distinguish it from the bright, or drawn-wire,) is made, may be readily conceived. For the rims of pots, kettles, and other kinds of "hollow ware," as made by the tinmen or braziers, wherein the copper or tinned plate is wrapped round the wire, the black wire is equally useful with the bright; for these purposes, and all others where the wire is hidden, or is to be painted, the rolled black wire is preferred, on account of its greatly inferior cost.
Whether wire be drawn by water, steam, or hand-power, the process is nearly the same, and the tools very similar. In order to get the end of the wire through the first reducing hole in the draw-plate, it is sharpened by hammering or filing; being then inserted through the plate, the latter is laid so as to take its bearing against two stout pins fixed vertically in a solid, firm, bench, and the end of the wire is griped by a pair of pincers attached to a chain; the cross lever of these pincers are so formed, that the chain when pulled has a tendency to draw them together, and in proportion to the force applied to them, do they bite or gripe the wire; by means of a powerful lever the wire is now drawn through the hole in the plate', which is well lubricated with grease; and when a sufficient extent has been thus drawn through, the end of the wire is fastened to a cylinder to which the power is applied, and the wire coiled upon it as it comes through the plate. The new wire thus drawn is very stiff and hard, and requires annealing prior to the next drawing process.
When annealed it is put into a vessel containing an acid liquor, and then scoured bright before it is passed through a second or smaller hole, in which the operation is repeated as many times as may be found necessary to reduce it to the size required, - annealing, treating with acid, and scouring, at every succeeding operation. It is said, that in order to heat this acid liquor, at an eminent manufactory, some ingots of brass which were at hand were heated red hot and quenched in it. It was afterwards found that the iron wire treated with this acid liquor, was covered with a thin film of copper, (derived from a slight solution of the heated ingot to the acid,) and that the wire was in consequence drawn through the plates with much greater facility than usual, the copper evidently acting as a lubrication to decrease the attrition between the wire and the draw-plate. In consequence of this accidental discovery, the practice has been since continued at the manufactory, of employing a weak solution of copper in the acid liquor used in iron and steel wire-drawing. The slight coat of copper is got rid of in the last annealing process.
To produce a perfect and durable wire-drawing plate, is a work of considerable art; and British skill has in this respect been long surpassed by the French, from whom all our best "draw-plates " are obtained. The process by which our ingenious neighbours attain their superiority, must therefore be of sufficient importance to our countrymen, to entitle it to a place in our work. In vol. xv. of Les Arts et Metiers is the following account of the process, by M. Du. Hamel.