COOPERAGE, the art of making vessels of pieces of wood bound together by hoops. It is a very ancient art. such vessels having been in use among the Romans at the period of the Christians era. The upright pieces forming the sides of a barrel, or cask, or other cooper's work, are called staves; and, as casks are usually larger in the middle than at the top and bottom, this swelling, called the belly or lroulge, is formed by skillfully shap ing each stave so that it shall form part of the required' double conoid, and 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 narrowed down in a curved line towards each end. A skillful cooper can work this curve so accurately that no further fitting or alteration shall be 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 com pressed 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 vessels for holding liquids. The dry cooper does inferior 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 work is made of oak, which must be thoroughly dried before being put together. In warm countries, the drying of the sun is sufficient, and casks are therefore mounted in summer only; but in britain, artificial 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 contraction on cooling may bind the work together.