COOPERAGE (from coop, AS. eypa, OS. cCpu, 011G. chuofa, Ger. .liufe, vat, from ML. copa, Lat. cu pa, vat, Gk. KOrv, kype, bole, Skt. 1,47pa, well). The art of making vessels of pieces of wood bound together by hoops. It is a very an cient art, such vessels having been in use among the Romans at the beginning of the Christian Era. The upright pieces forming the sides of a barrel, or cask, or other cooper's work, are called stares; and, as casks are usually larger in the middle than at the top and bottom, this swelling, called the belly or bulge, is formed by skillfully shaping each stave so that it shall form part of the required double colloid, and so that, when all are built and hooped together. their edges shall coincide perfectly. For this purpose, each stave is made broadest in the middle. and nar rowed down in a curved line toward each end. A skillful cooper can produce this curve so accu rately that no further fitting or alteration is needed when the staves are put together. The staves are made to meet at their inner edges. and by driving the hoops very hard, the inner part is compressed until the slight gaping outside is closed, and thus slight inaccuracies of fitting are remedied. There are several branches of cooperage. The wet or tight cooper makes ves sels for holding liquids. The dry cooper does in ferior work, such as barrels for containing dry goods, where an inferior degree of accuracy is sufficient. The white cooper makes churns, pails, etc., which for the most part have straight sides. The best wood to employ is oak, which must be thoroughly dried before the staves are put to gether. In warm countries the drying of the sun is sufficient. and casks are therefore mounted in summer only: but in northern countries arti ficial drying is commonly resorted to. The hoops are hammered down from the narrow to the wide part of the cask. by means of a mallet striking a piece of wood held against the hoop. Iron hoops are sometimes put on hot, in order that their con traction on cooling may hind the work together.
Like most other processes of manufacture. the cooper's trade has changed in modern times, with the substitution of machinery for hand work. The machinery used is commonly termed barrel making machinery; but it is employed, with suitable modifications, in making casks and kegs as well as barrels. Barrel-making machinery may be divided into machines for the ulannfac ture of staves, machines for manufacturing heeds. and machines for setting, up and finishing the barrel. The saw used for cutting staves is a cylindrical sheet, having teeth upon one end ; the blocks of wood are clamped in the usual manner, and the staves fall within the cylinder. They are then laid upon an endless conveyer, which carries them against two circular saws that cut them a definite length. Each piece is
then plaeed in a pair of clamps, and moved against a rotary wheel provided with cutters, that dress the edge to the required bilge and bevel; the bilge is the increased width midway between the ends, which causes the enlarged diameter of the cask at the middle; the beret is the angle given to the edge conforming to the radius of the cask. The surface of the stave is smoothed by passing it under revolving cut ters; a recent form of machine takes ofi' the sur plus wood from riven staves without cutting across the grain, following winding or crooked pieces as they are split from the block. The heads are usually made of several fiat pieces jointed and fastened with dowels, or pins of wood. The edge of each piece is pushed against the side of a rotary disk, provided with cutters that instantly straighten it; it is then pushed against bits that bore holes for the pins to be afterwards inserted by hand. Several boards being pinned together, enough to make a head. the whole is first smoothed on one side and dressed to a uniform thickness; then it is clamped between two disks, and, as these disks turn, a saw trims the head into a circle with a beveled edge; if the wood is green, an oval form may be given to provide against shrinking.
The barrel has next to be 'set up.' A sufficient number of staves are set into a frame, their edges refitted if necessary: stout iron hoops, called 'truss hoops.' pushed up from below grasp the lower ends tightly, and the whole may be lifted from the mold. One end of the barrel is formed, but the other end is open and flaring. A rope is passed about the open end and taken to a windlass, and the staves arc drawn together by tightening the rope: in this stage the barrel is heated, to cause the staves to yield snore easily to their required form. The barrel is now leveled by placing it upon a horizontal bed and bringing down upon it a powerful disk that presses upon its ends and forces the staves into their proper position. A machine is devised which trusses and levels the barrel at a single movement. The slack barrel stands in its truss hoops, two on each end; those of the lower end rest on strong supports; those of the upper end are seized by hooks whose handles pass down through the platform to a common level : when all the parts are in place, powerful machinery pulls the upper trusses down, at once driving the barrel into the lower trusses. drawing together both ends, and leveling the whole. Each end of the shell, thus made, passes under a rotary cutter which forms a croze, or groove. to receive the head, and chamfers, or bevels, the ends of the staves. The heads are put in and the hoops set. by hand. The barrel is then made to turn under a smoothing tool and rapidly finished.