Steel is a carburet of iron, and possesses some remarkable properties, by which it is distinguished from common iron. It is of such a superior degree of hardness, that it is capable of filing the latter; it strikes fire with siliceous stones, and scratches the hardest glass; it is heavier, emits a stronger sound, exhibits on fracture a finer grain, assumes a brighter white lustre when polished, is susceptible of greater elasticity; becomes more slowly magnetic, but retains that power longer; does not so easily acquire rust; in the fire it assumes various strong tints, and when heated is speedily cooled in cold water, but is then harder, more brittle and less pliable. In consequence of these qualities it is fit for many uses to which common iron either cannot be applied, or is less proper.

It is certain that the invention of steel is of very great antiquity. In the Old Testament, however, the mention of it is very doubtful, according to Professor Tychsen, whose remarks on this subject I subjoin in a note below806; but it appears that it was used as early as the time of Homer, and that the Greeks gave to it different names, one of the most common of which was stomoma, though it seems certain that this word did not so much denote steel itself as the steeled part of an instrument, or the operation of steeling. The name chalybs was given to steel from the Chalybes, a people on the southern shore of the Pontus Euxinus, between Colchis and Paphlagonia, who had considerable mines, and in particular iron and steel works: though others, on the contrary, derive the name of the people from the principal article of their commerce. This derivation appears the more probable, as Justin says that a river of Spain, on which there were steel works, was named Chalybs, but at a much later period. Some also have ascribed to the Chalybes the invention of iron, which however is much older.

But it seems to be less known that adamas also at first denoted steel. This is expressly said by Hesychius, and many epithets derived from adamas are applied to articles made of steel or of iron. Among these may be mentioned the helmet of Hercules, in Hesiod807, and the so-called adamantine chains, gates, and bars of the poets, which in dictionaries are always explained as consisting of precious stones.

It was not till a late period that this word was applied to the most costly of all the precious stones. In this sense it occurs neither in Homer, Hesiod, Herodotus, Orpheus, nor Dioscorides, though the first of these writers often describes various kinds of valuable ornaments. Goguet and others thence conclude that the diamond was not then known. At present I cannot enter into the history of this stone; but I must own, that I consider the knowledge of it to be older, and suspect that it was first introduced under another name, and is mentioned by Orpheus and some others under that of jasper (jaspis). This poet compares his jaspis to rock crystal, and says that it kindles fire in the same manner. That he knew how to use rock crystal as a burning-glass, he expressly tells us himself; but he certainly could not procure a diamond of such a size as to be able to burn with it. From its vitreous nature however he conjectured, and very properly, that it might be employed for that purpose. He calls the jaspis transparent, compares it to glass, and says that it had that sky colour which at present is named color hyalinus. This is probably the reason why Dioscorides and others call some kinds of jasper transparent and sky-coloured. The jaspis in the Revelation of St. John808, described as a costly transparent crystalline kind of stone, was perhaps our diamond, which afterwards was everywhere distinguished by that name.

The Romans borrowed from the Greeks the word chalybs; and in consequence of a passage in Pliny809, many believe that they gave also to steel the name of acies, from which the Italians made their acciajo, and the French their acier. The word acies, however, denoted properly the steeled or cutting part only of an instrument. From this, in later times, was formed aciarium, for the steel which gave the instrument its sharpness, and also aciare to steel810.

At present there are two methods of making steel; the first of which is by fusion either from iron-stone or raw iron, and the second by cementation. I have never found in the works of the ancients any traces of steel prepared by cementation; nor am I acquainted with the antiquity of that process, though the ancients, without knowing it, employed it for brass. Spielman says811, that Pliny in one part calls it tostio; but this word occurs neither in Pliny nor in any ancient writer. It is however possible that the word torrere may somewhere signify cementation, but I have not yet met with an instance of it.

The preparation however by fusion, as practised by the Chalybes, has been twice described by Aristotle; but as I have already given in another work812 everything I was able to collect towards an explanation of these passages, I shall not here repeat it. I shall only remark, that the steel of the ancients, in consequence of not being cemented, suffered itself to be hammered, and was not nearly so brittle as the hardest with which we are acquainted at present.

On the other hand, the singular method of preparing steel employed by the Celtiberians, in Spain, deserves to be here described. According to the account of Diodorus813 and Plutarch814, the iron was buried in the earth, and left in that situation till the greater part of it was converted into rust. What remained, without being oxydized, was afterwards forged and made into weapons, and particularly swords, with which they could cut asunder bones, shields, and helmets. However improbable this may appear, it is nevertheless the process still used in Japan; and Swedenborg has introduced it among the different methods of making steel815.

The art of hardening steel by immersing it suddenly, when red-hot, in cold water, is very old816. Homer says, that when Ulysses bored out the eye of Polyphemus with a burning stake, it hissed in the same manner as water when the smith immerses in it a piece of red-hot iron, in order to harden it817. Sophocles uses the comparison of being hardened like immersed iron818; and Salmasius819 quotes a work of an old Greek chemist, who treats on the method of hardening iron in India. It is also a very ancient opinion, that the hardening depends chiefly on the nature of the water. Many rivers and wells were therefore in great reputation, so that steel works were often erected near them, though at a considerable distance from the mines. Instances of this may be found in Pliny820 and in Justin821. The more delicate articles of iron were not quenched in water, but in oil.

An opinion, it is well known, long prevailed, that there were various fluids and mixtures which communicate to steel different degrees of hardness, and every artist thought he knew a peculiar hardening kind of water, the preparation of which he kept a secret. This notion is by some still maintained822; because there are often found stones cut by the ancients, which the moderns, on account of their hardness, as is believed, have seldom ventured to touch. Of this kind is the hardest porphyry. There are people who still endeavour to find out that hardening kind of water, in which the ancients prepared their tools for cutting such stones. According to Vasari823, that water was actually discovered by the archduke Cosmo, in the year 1555. Among a large collection of stones he had a block of porphyry, from which he wished a bason to be made for a well, but was told by the most experienced artists that it was impossible. On this, says Vasari, in order to render the work possible, he prepared from certain herbs, which he does not name, a water wherein the red-hot tools were quenched, and by these means so hardened, that they were capable of cutting porphyry. With tools tempered in this manner the artist Francesco del Tadda not only made the required bason, but various other curious articles824.

Winkelman, therefore, does injustice to Vasari when he says, “Vasari, in pretending that Cosmo archduke of Tuscany discovered a water for making porphyry soft, betrays childish credulity.” On the contrary, he very properly asserts that there is no water of such a quality as to soften porphyry; though Porta and many old writers imagined that they were acquainted with one capable of producing on that stone, which they considered as a species of marble, the same effects as an acid does on the latter. But Vasari says nothing of the kind.

After Tadda’s death, the art of cutting porphyry came to Raphael Curradi, who communicated to Dominico Corsi this secret, which was afterwards employed by Cosimo Silvestrini825. I, however, agree in opinion with Winkelman and Fiorillo, our learned connoisseur in the arts, that the method of working porphyry was known in every age, even in the most barbarous, though artists, no doubt, preferred working on other stones which were less brittle and hard. We know however from the latest researches, that all the kinds of hardening water hitherto invented are in nothing superior to common water; and that in hardening more depends on the nature of the steel, or rather on the degree of heat, than on the water; although it is true that the workman does right when he adds to the water a thin cake of grease, or pours over it hot oil, through which the steel must necessarily pass before it enters the water, for by these means it is prevented from acquiring cracks and flaws.

The invention of converting bar iron into steel by dipping it into other fused iron, and suffering it to remain there several hours, is commonly ascribed to Reaumur826. But this process is mentioned by Agricola, Imperati and others, as a thing well-known and practised in their time.

Pliny, Daimachus827 and other ancient writers mention various countries and places which, in their time, produced excellent steel. Among the dearest kinds were the ferrum Indicum and Sericum. The former appears to be the ferrum candidum, a hundred talents of which were given as a present to Alexander in India828. Is it not probable that this was the excellent kind of steel still common in that country, and known under the name of wootz, some pieces of which were sent from Bombay in the year 1795 to the Royal Society of London? Its silver-coloured appearance when polished may have, perhaps, given occasion to the epithet of candidum. The method of preparing it is still unknown, but it is supposed to be a kind of fused steel829. This however is a mere conjecture, unsupported by any proofs830. At what time was damasked steel obtained from the Levant? [Three kinds of steel are now principally manufactured; bar or blistered steel, shear steel and cast steel.

The bar or blistered steel is made by the process of cementation: this consists in putting bars of the purest malleable iron alternately with layers of charcoal or soot into a proper furnace; the air being carefully excluded and the whole kept at a red heat for several days. By this process the carbon combines with the iron, altering its texture from fibrous to granular or crystalline, and rendering the surface blistered. The action of the carbon occasions fissures and cavities in the substance of the bars, rendering them unfit for tool-making, until they are condensed and rendered uniform by the operation of tilting, i. e. compression by a powerful hammer worked by machinery.

Shear steel is made by breaking up bars of blistered steel into lengths of about 18 inches, and binding four or six of them together with a steel rod, and then heating them to a full welding heat, the surface being covered with fine clay or sand to prevent oxidation. They are then drawn out into a bar, hammered, tilted and rolled. In this state it is susceptible of a much finer polish, and is also more tenacious and malleable, and fit for making strong springs, knives, &c.

Cast steel, which was first made by Mr. Huntsman at Attercliff, Sheffield, in 1770, is made by melting blistered steel, casting it into ingots and rolling it into bars. In this condition its texture is much more uniform, closer and finer grained. The different degrees of hardness required for steel are given by the process called tempering, which is effected by heating the steel up to a certain temperature, and then quenching it suddenly in cold water. Its hardness and brittleness are thus much increased, but it may be again softened by exposure to heat simply.]