Pencils. A slender stick of black lead, slate, or coloured chalk, encased in a small round piece of wood, is called a pencil; but the term is also applied to small hair-brushes used by artists, and it was to these that the name was originally given. Some early manuscripts have lines upon them ruled with ordinary metallic lead. When pencils of Black Lead (q.v.), called also graphite and plumbago, were first used is uncertain, but Beckmann points out that they are distinctly mentioned in a book on fossils by Conrad Gesner, printed at Zurich in 1565. The discovery of the use of black lead as a material for writing or drawing with was an important one, since for work where words or lines may require to be frequently rubbed out no other substance has such valuable properties.
For a long time the plumbago from the Borrowdale mines in Cumberland furnished the 'leads' for the best pencils ever made. These mines have been exhausted since 1850; but when the graphite from them was available it had, in the case of the larger and purer pieces, only to be cut into square rods of the proper size for pencils. In order to work up the smaller bits, cuttings, and dust of this precious material, Mr W. Brockedon, in 1843, patented a method by which he first reduced these small pieces to powder, and then, by subjecting it to great pressure in dies from which air is exhausted, produced a cake as solid and compact as the natural graphite, and equally suitable for cutting into leads. For a considerable number of years past, owing to the Borrowdale plumbago being worked out, black-lead pencils, as well as coloured pencils or crayons, have been made by the process invented about the close of the 18th century by Conté of Paris, which consists in thoroughly mixing the black lead with clay, both being first reduced to a state of fine division and most carefully purified. The proportions of graphite and clay vary from two of the latter to one of the former (for light hard pencils) to equal parts of the two ingredients (for the dark soft kinds). Water is added to the mixture, which is repeatedly ground, and then placed in canvas bags and squeezed in a hydraulic or steam press till it acquires the consistency of stiff dough. In this state it is placed in a strong metal cylinder, whose bottom is perforated with apertures of the proper size for the section of the pencil leads. The black-lead mixture, being in a plastic state, is then squeezed out through the apertures by a plunger into continuous strips or threads, which are arranged in straight lengths on a board to dry. After being exposed to a slight artificial heat, the strips are cut into the usual lengths for pencils, and placed in a covered crucible, which is raised to a red heat. When cooled they are ready for use.
An extensive mine of fine graphite was opened at Bogodolsk in eastern Siberia about 1850. Much of this black lead is scarcely if at all inferior in quality to that formerly obtained in Cumberland. Pencils have been made from this graphite in the unmixed state, and Faber of Nuremberg still makes fine pencils of it. These have the words 'Graphite de Siberie' stamped upon them. Dixon's American graphite pencils are made from the plumbago found at Ticonderoga on Lake George, but it is mixed with clay as above described. Workable deposits of graphite are found at several places in Canada. A good deal of what occurs in the township of Buckingham, in the province of Quebec, is almost pure, and is made into pencils. For other localities, see BLACK LEAD.
The wood used for pencils is invariably that of the Virginian or Florida cedar (see JUNIPER), which, being straight grained and easily cut, is remarkably well suited for the purpose. Two rectangular pieces of the proper size, cut out by machinery, go to make a pencil, the one containing the groove for the lead being thicker than the other. After the lead is inserted the two pieces are glued together, and then cut to a round shape by revolving cutters. The operations of cutting out the square fillets of wood and rounding them after they are glued are very rapidly performed. Pencils are sometimes cut in a hexagonal shape. Besides the maker's name, letters indicating the character of the lead are stamped upon pencils. For Great Britain these are H, HH, HHH, B, BB, BBB, HB, and F. H signifies hard; once and twice repeated it means harder and very hard. B stands for black (and soft), and, when repeated, for still blacker. HB, the most generally useful, means hard and black; while F signifies firm. In the United States the letters used differ somewhat. They are H, hard; VH, very hard; VVH, still harder; S, soft; VS, very soft; VVS, still softer, for deep black shading; M, medium; MH, medium hard; MB, medium black.
Owing to the multiplicity of processes for reproducing pen-and-ink drawings (see ILLUSTRATION), and the cultivation of that method for book illustration, the black-lead pencil is much less used now than in the earlier half of the 19th century. Drawings in chalk or charcoal, since either material makes a much blacker line, have usually deeper and more effective shading than can be given with pencil. Still, a finished drawing in black lead by a skilled hand has charms of its own, and it is to be regretted that so few of these of any importance are now made by artists of high standing.
Coloured pencils are made with ordinary pigments—e.g. Prussian blue and chrome yellow for their respective colours—mixed with white wax and tallow or with gum and tallow, clay being sometimes added; but none of these coloured preparations are heated like those made of graphite and clay. Copying and ink pencils are made of a concentrated solution of an aniline violet added to a mixture of graphite and China clay. For some kinds gum is added, and in such cases graphite is sometimes omitted.
The arrangement of a small rod of black lead, which is kept projecting as it wears away from a tube fitted to a metal pencil-case, and which has since been so much used, was patented by Hawkins and Mordan in 1822. An alloy of lead, antimony, and a little mercury is made into ever-pointed pencils for writing on paper prepared with a suitable surface.
The manufacture of black-lead and coloured pencils is carried on most extensively at Nuremberg, where there are more than a score of factories, employing in all nearly 6000 hands, and producing annually some 250 million pencils, worth about £420,000. Faber founded a branch in New York in 1861. Four years later the Eagle and American Pencil Companies were established, and the other surviving firm, the Dixon Crucible Company, in 1872.