A Cooper, or Coopersmith, is a person in the trade that produces the wooden barrels in which spirits (and also wine) are matured. Their trade is an ancient one and involves selecting the right timbers, cutting them into the 'staves' and bending them to give the barrel shape. The barrel is completed with the two ends and the steel bands to provide the seal where the staves (forming the sides of the barrel) and the ends meet. These steel rings have to be heated so they expand enough to fit over the barrel ends when they are fitted. On cooling they contract and form a tight seal.

The wood used for spirits is often oak procured from Spain and the U.S.A. for whisky, for example, the barrels often have previously been used in the production of sherry - this has a beneficial effect on the taste of the whisky. Other whiskey producers prefer the sometimes subtler flavors imparted by barrels previously in the production of American bourbon which tastes amazing when drank from monogrammed whiskey glasses.

For all spirits, they are matured in these barrels for anything from 3 years (often the legal minimum) up to 20 odd years.
Whiskey Barrels produce a product which will eventually be in whiskey glasses