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 below[806]; 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 Hesiod[807], 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. John[808], 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 Pliny[809], 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 steel[810].
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 says[811], 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 work[812] 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 Diodorus[813] and Plutarch[814], 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 steel[815].
The art of hardening steel by immersing it suddenly, when red-hot,
in cold water, is very old[816]. 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 it[817]. Sophocles uses the comparison of
being hardened like immersed iron[818]; and Salmasius[819] 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 Pliny[820] and in Justin[821]. 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 maintained[822]; 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 Vasari[823], 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 articles[824].
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 Silvestrini[825]. 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 Reaumur[826]. But this process is mentioned by
Agricola, Imperati and others, as a thing well-known and practised in
their time.
Pliny, Daimachus[827] 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 India[828]. 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 steel[829].
This however is a mere conjecture, unsupported by any proofs[830]. 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.]