PENCIL MANUFACTURE 531 



them aside to dry, When dried they are ready for being rounded. The rounding is 

 done by an apparatus fixed to a bench, containing revolving planes or turning tools. 

 Into this engine, rods are put one after another, and out they come as fast as the 

 eye can follow them, rounded to a perfect nicety. By this simple and efficient 

 machine a man will round from six hundred to eight hundred dozens of pencils in a 

 day. After being rounded they get a smoothing with a plane, and then they are 

 polished by being rubbed with a peculiar kind of fish-skin ; this latter operation being 

 performed by girls. Being polished, the next step is to cut the rods into lengths with 

 a circular saw, after which the lengths are respectively smoothed at the ends. 

 Nothing now remains but to stamp the name of the maker, with the letters significant 

 of their quality. The stamping-engine is as ingenious a piece of machinery as is in 

 the establishment. Fed into it, the pencils are stamped in less than an instant of 

 time. A girl will with this apparatus stamp two hundred pencils per minute. 

 Gathered from a box below into which the pencils fall, they are carried away to be 

 tied in bundles. 



In the year 1795 M. Conte invented an ingenious process for making artificial 

 black-lead pencils. 



Pure clay, or clay containing the smallest proportion of calcareous or siliceous 

 matter, is the substance which he employed to give aggregation and solidity, not only 

 to plumbago-dust, but to all sorts of coloured powders. That earth has the property 

 of diminishing in bulk and increasing in hardness, in proportion to the degree of 

 heat it is exposed to, and hence may be made to give every degree of solidity to 

 crayons. The clay is prepared by diffusing it in large tubs through clear river-water, 

 and letting the thin mixture settle for two minutes. The supernatant milky liquor is 

 drawn off by a syphon from near the surface, so that only the finest particles of clay 

 are transferred into the second tub, iipon a lower level. The sediment, which falls 

 very slowly in this tub, is extremely soft and plastic. The clear water being run off, 

 the deposit is placed upon a linen filter, and allowed to dry. It is now ready for 

 use. 



The plumbago must be reduced to a fine powder in an iron mortar, then put into a 

 crucible, and calcined at a heat approaching to whiteness. The action of the fire 

 gives it a brilliancy and softness which it would not otherwise possess, and prevents 

 it from being affected by the clay, which it is apt to be in its natural state. The less 

 clay is mixed with the plumbago, and the less the mixture is calcined, the softer are 

 the pencils made of it; the more clay is used, the harder are the pencils. Some of 

 the best pencils made by M. Conte were formed of two parts of plumbago and three 

 parts of clay ; others of equal parts. This composition admits of indefinite variations, 

 both as to the shade and hardness advantages not possessed by the native mineral. 



The materials having been carefully sifted, a little of the clay is to be mixed with 

 the plumbago, and the mixture is to be triturated with water into a perfectly uniform 

 paste. A portion of this paste may be tested by calcination. If on cutting the in- 

 durated mass particles of plumbago appear, the whole must be further levigated. The 

 remainder of the clay is now to be introduced, and the paste is to be ground with a 

 muller upon a porphyry slab, till it be quite homogeneous, and of the consistence of 

 thin dough. It is now to be made into a ball, put upon a support, and placed under 

 a bell glass inverted in a basin of water, so as to be exposed merely to the moist air. 



Small grooves are to be made in a smooth board, similar to the pencil parallele- 

 pipeds, but a little longer and wider, to allow for the contraction of volume. The wood 

 must be boiled in grease, to prevent the paste from sticking to it. The above- 

 described paste being pressed with a spatula into these grooves, another board, also 

 boiled in grease, is to be laid over them very closely, and secured by means of screw- 

 clamps. As the atmospheric air can get access only to the ends of the grooves, the 

 ends of the pencil-pieces become dry first, and by their contraction in volume get loose 

 in the grooves, allowing the air to insinuate further, and to dry the remainder of the 

 paste in succession. When the whole piece is dried, it becomes loose, and might be 

 turned out of the grooves. But before this is done, the mould must be put into an 

 oven moderately heated, in order to render the pencil-pieces still drier. The mould 

 should now be taken out, and emptied upon a table covered with cloth. The greater 

 part of the pieces will be entire, and only a few will have been broken if the above 

 precautions have been duly observed. They are all, however, perfectly straight, 

 which is a matter of the first importance. 



In order to give solidity to these pencils, they must be set upright in a crucible till 

 it is filled with them, and then surrounded with charcoal-powder, fine sand, or sifted 

 wood-ashes. The crucible, after having a luted cover applied, is to be put into a fur- 

 nace, and exposed to a degree of heat regulated by the pyrometer of Wedgwood ; 

 which degree is proportional to the intended hardness of the pencils. When they 



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