Almost all irons are improved by admixture with others, and, therefore, when superior castings are required they should not be run direct from the smelting furnace, but the metal should be remelted in a cupola furnace, which gives the opportunity of suiting the quality of the iron to its intended use. Thus, for delicate ornamental work, a soft and very fluid iron will be required, whilst for girders and castings exposed to cross strain the metal will require to be harder and more tenacious. For bed-plates and castings which have merely to sustain a compressing force, the chief point to be attended to is the hardness of the metal.
Castings should be allowed to remain in the sand until cool, as the quality of the metal is greatly injured by the rapid and irregular cooling which takes place from exposure to air if removed from the moulds in a red hot state, which is sometimes done in small foundries to economise room.
THE BLACKSMITH.
FORGE.
In the building and fitting of the house a large portion of the iron work will have to be furnished by the Smith, and as we have already given some description of iron founding, it will be necessary to say something about the Blacksmith, or the worker in iron or black metal, whose business is different from that of the whitesmith, which has to do more particularly with white or yellow metal.
The way in which malleable iron, that is, iron fit for the hammer, is produced has been mentioned in connexion with the trade of the iron founder, who in fact supplies the Blacksmith with the raw material. It is not very easy to tell you much about the way in which the Blacksmith makes the great variety of articles which his trade furnishes, for there is no business the success of which depends more upon personal skill. As the trade of the Smith, or at all events the worker in metal, is one of the most ancient, and existed in times when there were few tools,—as, in fact, it is the Smith who has to make tools,—so at the present day, he has to depend chiefly on his own ability in the use of the hammer and a few other simple instruments to fashion the articles that come out of his workshop.
It is he who supplies the various articles of wrought iron work used in a building; as pileshoes, straps, screw bolts, dog-irons, chimney-bars, gratings, and wrought-iron railings and balustrades for staircases. Wrought iron was formerly much used for many purposes for which cast iron is now generally employed; the improvements made in casting during the present century having caused a great alteration in this respect. It is not only for building purposes that the Blacksmith is employed, however, since there is scarcely anything constructed of iron in which his aid is not required, from important portions of machinery to the rough horse-shoes which have to be finished and fitted by the farrier. In the forge, where the great bellows suspended to the ceiling make the furnace roar, and the sparks fly, the clinking of hammers is heard all day long.