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Slate-pen′cil.

The common irregularly shaped black slate-pencils, once the only kind known, are made in Germany. These have been pretty much superseded in this country by the softer, neater, and greatly superior article, known as soapstone pencils, made from a peculiar stone found near Castleton, Vt. This stone contains over 50 per cent of silica, a large proportion of alumina, and also some potash and iron; and, while having some resemblance to soapstone, more nearly resembles slate in texture and capability of being split readily into plates.

In the manufacture of pencils, it is first split into slabs 1 to 2 inches thick, which are then sawn into blocks 6 to 7 inches long and 4 or 5 inches wide. With a thin blade of steel and a hammer these are split into plates about one third of an inch thick, which are next passed between two flat-edged knives to plane them. The plate is then fed to a machine in which it is passed successively beneath a series of grooved cutters, each of which cuts a row of deeper incisions into the slab, until, on emerging from the machine, its upper side is covered with convex flutings, the channels between which penetrate half through the stone. It is then transferred to a second machine, where its other side is subjected to the action of a series of similar cutters, by which the pencils are completely rounded and separated from each other. They are next sawed to uniform lengths, the sizes varying from 3 1/2 to 6 inches; and, finally, pointed on a grindstone. In some cases they are afterward painted.

The dust and waste, which is said to amount to 90 per cent of the original material, is utilized by grinding to an impalpable powder, which is used for mixing with paper-pulp to give it body and enable it to receive a satin surface.

As the stone contains over 30 per cent of alumina, the refuse is also available for the manufacture of alum.

1877.

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Castleton (Vermont, United States) (1)

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