Without entering into the details of the manufacture of iron and steel, which would be out of place here, there are many matters relating to the subsequent modifications and applications of these metals not readily to be found in the general literature of the subject. These will receive attention.
(1) Bright steel surfaces may be ornamented with initials, a cipher, or a pattern, by the following process:- If the ornament is to be bright upon a dead ground, take a camel - hair pencil and draw with it upon the steel the letters or patterns in Brunswick black. If the ornament is to be dead upon a bright ground, the letters or patterns must be left untouched, and the whole of the ground painted over with the pigment. A little aquafortis (dilute nitric acid) is then poured upon the exposed parts of the steel, and in a few minutes it will be seen to have eaten sufficiently into the metal. When this is done, wash off the aquafortis with water, and remove the Brunswick black with turpentine. A pretty variety in steel decoration may be made by introducing blue ornaments. Steel may be rendered a beautiful blue by exposure to heat, and the blue colour can be removed, where it is not required in the pattern, with white wine vinegar or other weak acid, the parts to remain blue being protected as before with Brunswick black. On the parts from which the blue is removed, further variety may be gained by painting additional ornaments in Brunswick black, and exposing the remainder of the ground to the action of the aquafortis.
If the parts which receive these latter ornaments are afterwards polished, the pattern will present 3 varieties, viz., bright blue, bright white, and dead white. Gilding on steel was formerly done with spirit; now, if the operator can conveniently send his work to an electro - gilder's, he will find it well to do so, first painting over with Brunswick black, those parts which are not to be gilt. Or the gilding may be performed at home by the following method:- If sulphuric ether and nitro-muriate of gold are mixed together, the ether will, by degrees, remove from the acid nearly the whole of the gold, and retain it for a long time in solution. Take ether thus charged, and with the camel - hair pencil paint over the parts of the design intended to be in gold; after giving the ether time to evaporate, rub over the parts thus gilt with a burnisher. After the completion of the design, the bright surface of the steel may be restored, in any place where it has become dim, by rubbing with a little whiting. (Cassell's Household Guide,)
By damascened steel is meant that sort of steel which receives shades of darker and lighter colour after the surface has been corroded with acids: it is remarkable, when genuine, for its elasticity, strength, and homogeneous fracture when broken.
(a) Natural Damascus steel comes from India and Persia, is distinguished by its excellent quality and mixed vein - ing, and is worked up principally into sword blades. These Oriental blades consist of a more highly carburetted steel than any European manufacture seems to possess, and in which, by skilful cooling, a division of 2 different carburets has taken place. This separation is clearly visible on corrosion with acids, as the parts subjected to the action of the acid are deepened and dyed by the exposure of the carbon, and, with the other less affected and consequently brighter parts, produce a design, more or less delicate, of grey and white lines, which often have a certain degree of regularity. A distinction is made between parallel striping or waving lines and mosaic damascening. If the cast - steel is made in iron moulds, as usual, the above separations do not take place. By re - welding and sudden cooling, the Damascus steel loses its pattern, The Indian. Woolz, as especially used for sword-blades, contains foreign substances mixed with it-as nickel, tungstate of iron, or manganese - which are said to impart peculiar value. Few European smiths succeed in working up Indian steel, because they do not accurately know the temperature required for its treatment.
In consequence of the large amount of carbon it contains (7.18 per cent.), this can only be effected within certain climatic limits: if too high a temperature is exhibited, it breaks to pieces under the hammer; if too low, it assumes a hard and brittle character. The iron appears disposed to receive a considerable quantity of carbon, through the manganese combination.
(b) Artificial damascened steel. Attempts have been made, with more or less success, to imitate the real damascening, and the following methods have been suggested:-
Luynes imitated the Indian process; smelting soft iron with charcoal, tungstate of iron, nickel, and manganese, was highly successful. The manganese, more especially, produced damascened steel, and introduced a large quantity of carbon without injuring its malleability.
Brennt produces a most valuable damask, very closely resembling the real, by smelting 100 parts iron with 2 of lampblack, or by smelting cast - iron with oxidized iron filings.
Clouet, Hachette, and Mille smelt iron plates of different natures, harder and softer, together, and produce a damask remarkable for its elasticity and hardness, but not having the wavy damascening of the real blades.
All browning methods known at present, obtained by moistening iron with acid, copper, or iron solutions, permitting them to dry in air, brushing off the rust formed in this manner, and repeating the operation several times, only produce a more or less light or dark red - brown rust coating upon iron articles. BarfFs process, as well as that of heating iron articles in superheated aqueous vapour, only causes an iron protoxide layer upon iron.
These last - mentioned two methods have the farther defect that the protoxide of iron layer peels off in a short time, whereby rust is invited. Iron articles are easily coppered or brassed by dipping in copper solutions, or coppered or brassed by the galvanic method; these coatings also scale off after a short time, especially if the iron surface was not thoroughly cleaned, when exposed to the influence of moist air.
By the following process, it is easy to provide iron articles with a handsome bronze - coloured protoxide coating; it resists the influence of humidity pretty well, and besides this, the operator has it in his power to produce any desired bronze colour in a simple manner. The cleansed and scoured articles are exposed to the vapours of a heated mixture of concentrated hydrochloric and nitric acids (1 and 1) for 2 to 5 minutes; and then, without unnecessarily touching them, heated to a temperature of 572° to 662° F. (300° to 350° C). The heating is continued until the bronze colour becomes visible upon the articles. After they have been cooled, they are rubbed over with petroleum jelly, and again Heated until the jelly begins to decompose. After cooling, the article is anew rubbed over with petroleum jelly. If now the vapours from a mixture of concentrated hydrochloric and nitric acids are permitted to operate upon the iron article, light red - brown tones are obtained. However, if acetic acid is mixed with the before - mentioned acids, and the vapours are permitted to operate upon the iron, oxide coatings are obtained possessing a handsome bronze - yellow colour.
All gradations of colours from dark red - brown to light red - brown, or from light bronze - yellow to dark brown - yellow, are produced by varying the mixtures of the acids. T-rods, 4 1/2 ft. long, for iron boxes, coated with such oxide layers, after 10 months, during which time they were continuously exposed to the influence of the air of a laboratory constantly laden with acid vapours, do not betray the slightest traces of change. (Prof. Oser. Ding.