The graphite is taken in the lump from the mines and carried to the reducing mill, where it is ground or pulverized in stamp mills under water. The fine particles of graphite float away with the water through a number of tanks, collecting at the bottom of these reservoirs. It is packed in barrels in the form of dust and sent to the factory, where tens of thousands of lead pencils are turned out every day. The pulverized graphite is so fine that it really is dust; it is dingy in color, and smooth and oily to the touch. It is divided into various grades of fineness by floating it on water from one tank to another. The coarse dust sinks to the bottom of the first tank, the next finer, to the bottom of the next and so on down the line, the finest powder, for the finest pencils, settling in the last tank. In another series of tanks the German pipe clay, which is mixed with graphite to secure the different grades of hardness, is graded in the same manner by floating. The finest clay is mixed with the finest graphite, and the hardness of the pencil is secured by increasing the proportion of clay in the mixture. For medium grades seven parts, by weight, of clay are mixed with ten parts of graphite. The mixing is done under a grinding mill similar to that used in mixing paint, and water is added to facilitate the mixing. The grinding stones are about two feet in diameter and only the upper one revolves. After the graphite and clay are ground together the mixture is put into canvas bags and the water is squeezed out under hydraulic press, leaving the mass the consistency of putty. This plastic material is placed in the forming press, which is a small iron cylinder in which a solid plunger or piston works up and down. A steel plate having a hole the size and shape of the "lead", is put under the open end of the cullender, and the plunger, pressing down, forces the graphite through the hole, making a continuous thread or wire of graphite. As long as this thread is moist it is pliable, but it becomes brittle when dry, so it is handled rapidly. It is cut in three-lead lengths, straightened out, and then hardened in a crucible over a coal fire. The leads when taken from the crucible are ready for the wood. Pine is used for cheap pencils, an ordinary quality of red cedar is used for better pencils, and nothing but Florida Key cedar is used in the best. The sawmills at Tampa, Florida, cut the cedar blocks about seven inches long and these are sawed into strips wide enough for six pencils; but as pencils are made in halves, each strip is thick enough only for a half pencil. When these strips are received in the factory they are run through a machine which cuts in each one six grooves, round or square, and at the same time smooths the face of the wood. The filling of the strips is done by girls. The first one takes a grooved strip of wood in her left hand and a bunch of leads in her right. She spreads the leads out fan shape, and with one motion fills the six grooves with leads. Next to her sits another girl who takes the filled strip, and quickly and neatly lays on it another grooved strip, which has just been given a coat of glue by a third girl. The filled and glued strips are piled up and put in a press to dry. The ends of the strips are evened off under a sandpaper wheel, and then the strips are fed into a machine which cuts out the individual pencils, shapes them and delivers them smooth and ready for the color polish in six streams. The coloring is done in liquid dyes, after the pencils have been sent through the varnish machine. Then follows the stamping , finishing and counting. This latter work is done by quickly filling a board having 144 holes in it, thus counting out a gross of pencils. ARTIFICIAL ICE |
