Part 104

The Story in a Lead Pencil

Courtesy of The Scientific American.

Why Do They Call Them Lead-pencils?

~WHERE LEAD PENCILS COME FROM~

The lead-pencil so generally used today is not, as its name would imply, made from lead, but from graphite. It derives its name from the fact that prior to the time when pencils were made from graphite, metallic lead was employed for the purpose. Graphite was first used in pencils after the discovery in 1565 of the famous Cumberland mine in England. This graphite was of remarkable purity and could be used without further treatment by cutting it into thin slabs and encasing them in wood.

Who Made the First Lead-pencils in America?

For two centuries England enjoyed practically a monopoly of the lead-pencil industry. In the eighteenth century, however, the lead-pencil industry had found its way into Germany. In 1761, Caspar Faber, in the village of Stein, near the ancient city of Nuremberg, Bavaria, started in a modest way the manufacture of lead-pencils, and Nuremberg became and remained the center of the lead-pencil industry for more than a century. For five generations Faber’s descendants made lead-pencils. Up to the present day they have continued to devote their interest and energy to the development and perfection of pencil making. Eberhard Faber, a great-grandson of Caspar Faber, immigrated to this country, and, in 1849, established himself in New York City. In 1861, when the war tariff first went into effect, he erected his own pencil factory in New York City, and thus became the pioneer of the lead-pencil industry in this country. Since then four other firms have established pencil factories here. Wages, as compared to those paid in Germany, were very high, and Eberhard Faber realized the necessity of creating labor-saving machinery to overcome this handicap. Many automatic machines were invented which greatly simplified the methods of pencil making and improved the product. To-day American manufacturers supply nine-tenths of the home demand and have largely entered into the competition of the world’s markets.

What Are Lead-pencils Made of?

The principal raw materials that enter into the making of a lead-pencil are graphite, clay, cedar and rubber. Although graphite occurs in comparatively abundant quantities in many localities, it is rarely of sufficient purity to be available for pencil making. Oxides of iron, silicates and other impurities are found in the ore, all of which must be carefully separated to insure a smooth, serviceable material. The graphites found in Eastern Siberia, Mexico, Bohemia and Ceylon are principally used by manufacturers.

Pictures by courtesy Joseph Dixon Crucible Co.

FIG. 2.

FIG. 3.

Fig. 1 shows the shape in which the cedar slats arrive at the factory. These slats after grading are boiled in steam to remove what remaining sap there may be in the wood. The slats are then dried in steam-drying rooms. Then the next step is grooving and gives the results shown by Fig. 2. Now the wood is ready to receive the “leads” (which you will remember are a mixture of graphite and clay), which are placed between two slats sandwich fashion, glued, put in forms that hold them over night under a thousand pounds pressure. Fig. 3 shows the leads laid in one of the grooved slats.]

How Are Lead-pencils Made?

The graphite, as it comes from the mines, is broken into small pieces, the impure particles being separated by hand. It is then finely divided in large pulverizers and placed in tubs of water, so that the lighter particles of graphite float off from the heavier particles of impurities. This separating, in the cheaper grades, is also done by means of centrifugal machines, but the results are not as satisfactory. After separation, the graphite is filtered through filter-presses.

What Makes Some Pencils Hard and Others Soft?

The clay, after having been subjected to a similar process, is placed in mixers with the graphite, in proportions dependent upon the grade of hardness that is desired. A greater proportion of clay produces a greater degree of hardness; a lesser proportion increases the softness.

FIG. 5.

FIG. 6.

Fig. 4 shows a prospective view of the block as it appears when taken out of the form; the leads can be seen in the end. These blocks are fed to machines which cut out the pencils in one operation. An idea of this operation is given by Fig. 5, which shows a block half cut through. The pencils come out quite smooth, but are sand-papered to a finer finish before receiving the finishing coats. The finer grades of pencils are given from seven to nine coats of varnish before being passed along for the next process. Fig. 6 shows a pencil after it has been machined and before it has been varnished and stamped.]

Furthermore, the requisite degree of hardness is obtained by the subsequent operation, viz., the compressing of the lead and shaping it into form ready to be glued into the wood casings. A highly compressed lead will produce a pencil of greater wearing qualities, an important feature in a high-grade pencil. Hydraulic presses are used for this purpose; and the mixture of clay and graphite, which is still in a plastic condition and has been formed into loaves, is placed into these presses. The presses are provided with a die conforming to the caliber of the lead desired, through which die the material is forced. The die is usually cut from a sapphire or emerald or other very hard mineral substance, so that it will not wear away too quickly from the friction of the lead. The lead leaves the press in one continuous string, which is cut into the lengths required (usually seven inches for the ordinary size of pencil), is placed in crucibles, and fired in muffle furnaces. The lead is now ready for use, and receives only a wooden case to convert it into a pencil.

Where Does the Wooden Part of a Lead-pencil Come from?

The wood used in pencil making must be close and straight grained, soft, so that it can readily be whittled, and capable of taking a good polish. No better wood has been found than the red cedar, a native of the United States, a durable, compact and fragrant wood to-day almost exclusively used by pencil makers the world over. The best quality is obtained from the Southern States, Florida and Alabama in particular.

The wood is cut into slats about 7 inches long, 2¹⁄₂ inches wide, and ¹⁄₄ inch thick. It is then thoroughly dried in kilns to separate the excess of moisture and resin and to prevent subsequent warping. After this the slats are passed through automatic grooving machines, each slat receiving six semi-circular grooves, into which the leads are placed, while a second slab with similar grooves is brushed with glue and covered over the slat containing the leads. This is passed through a molding-machine, which turns out pencils shaped in the form desired, round, hexagon, etc. The pencils are now passed through sanding machines, to provide them with a smooth surface.

How is the Color Put on the Outside of the Pencil?

After sand-papering, which is a necessary preliminary to the coloring process, when fine finishes are desired, the pencils are varnished by one of several methods. That most commonly employed is the mechanical method by which the pencils are fed from hoppers one at a time through small apertures just large enough to admit the pencil. The varnish is applied to the pencil automatically while passing through, and the pencils are then deposited on a long belt or drying pan. They are carried slowly a distance of about twenty feet, the varnish deposited on the pencils meanwhile drying, and are emptied into a receptacle. When sufficient pencils have accumulated, they are taken back to the hopper of the machine and the operation repeated. This is done as often as is necessary to produce the desired finish. The better grades are passed through ten times or more. Another method is that of dipping in pans of varnish, the pencils being suspended by their ends from frames, immersed their entire length and withdrawn very slowly by machine. A smooth enameled effect is the result. The finest grades of pencils are polished by hand. This work requires considerable deftness; months of practice are necessary to develop a skilled workman. After being varnished, the pencils are passed through machines by which the accumulation of varnish is sand-papered from their ends. The ends are then trimmed by very sharp knives to give them a clean, finished appearance.

Stamping is the next operation. The gold or silver leaf is cut into narrow strips and laid on the pencil, whereupon the pencil is placed in a stamping press, and the heated steel die brought in contact with the leaf, causing the latter to adhere to the pencil where the letters of the die touch. The surplus leaf is removed, and, after a final cleaning the pencil is ready to be boxed, unless it is to be further embellished by the addition of a metal tip and rubber, or other attachment.

How is the Eraser Put On a Pencil?