SLAG.
Ironmasters, says a writer in “ Cassells’ Magazine,” are beginning to discern merits hitherto unsuspected in the sing or refuse of their blast furnaces. Till yesterday the heaps of rough cindery material which encumbered the ground overshadowed by tall brick chimneys, flame-topped, were regarded as rubbish of the worst sort. But now, ns mineral wool in America, as slag wool in Yorkshire, and as cotton silicate in Germany, this humbler Cinderella among products finds itself prized at last. Silica, or flint, as the manufacturer knows too well, is sure to be present in iron ore, and has to be got rid of, and for this reason he flings into the roaring furnace those cart-loads of broken limestone, the lime of which unites with the silica, and runs off, a lava stream, leaving behind it the saleable “ pigs ”of molten iron. Quite recently it was discovered that this lava stream, till now sheer lumber, could be manipulated into a fibrous substance, light, pliant, and bearing a remarkable similarity to wool, and perhaps still more so to the fine strong hair of the Himalayan shawl-goat. The hot slag, by ingenious contrivances, is made v/lnlo yet in a fluid state to develop, as it trickles forth, into vitreous threads. Of this slag-yarn there are three numbers, or qualities. Let us take the finest, No. 3, a cubic foot of which is but 81bs. in weight, while a cubic foot of the parent slag weighs no less than 192ibs. It is difficult, when surveying the huge bundles of woolly fibres first, to believe in the mineral origin of what looks so very like the carded fleece of sheep, and then to realise that the countless threads were drawn from a compact little slab of slag of equal weight from the imposing fibrous heap. Sometimes the wool is white, often grey, occasionally pink or red, and now and then green, or greenish-colored, as when it contains manganese. And now for its uses. In America it is chiefly valued because it is a non-conductor of heat, and in this capacity it far surpasses asbestos, felt, and every other substance employed in the arts. It enwraps boilers, it packs steam cylinders, and forms a fireproof jacket for liot-water piping; while, in virtue of the same quality, it is invaluable as a lining to the walla of an icehouse. It does duty also as a filter, and can readily be worked up into matting more durable than even the cocoa-palm yields. Clearly, however, higher destinies await this child of the blast furnace. Wool that is cheaply produced in any quantity, wool that defies moth and milldew, that is fireproof and almost indestructible, and which can keep in heat and keep out cold, must be available for carpets, tents, sails, packing-cloths and even overclothing. Improvements in what is after all an infant industry will probably suggest other uses for this mineral textile fabric, and if less romantic than the Golden Fleece of Jason, the Iron Fleece may one day become a standard and profitable staple of modern manufacturing skill.
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New Zealand Times, Volume XXXIII, Issue 5378, 22 June 1878, Page 2 (Supplement)
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510SLAG. New Zealand Times, Volume XXXIII, Issue 5378, 22 June 1878, Page 2 (Supplement)
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