The trees are specially selected and felled. After having laid in the open air for six months, they are put in a drying oven until the humidity in the wood is reduced to 12 per cent. The tree is then split into two and each part is sawn in half again to get four pieces.
From each piece, four staves are sawed in such a way that the orientation of the growth rings reduces the risk of a leaky barrel. The planks, approximately 38 inches long, are delivered to a cooperage and cut into staves of the desired length, as well as heads and ends. Both barrel ends are toasted lightly in a special oven. A new barrel is made (“raised”) using 29 to 31 staves, held together by a temporary ring.
It will then be steam-heated to make the wood more pliable. The barrel is tightened with a winch and fitted with temporary hoops that come from a large roll of flexible iron bands. Then it’s ready to be toasted and charred from the inside. When charring is done, the barrel is lightly scraped and the head and end are fitted, after which the barrel has to cool off. The temporary hoops are removed, and when the barrel is cooled enough, the permanent hoops – usually six in total – are placed on it.
The cooper bores the bung hole in the widest stave. A gallon of water is poured into the barrel, after which it is sealed with a rubber stop and pressurised to check for leakages. At the end of the production line, each barrel is inspected for quality and any existing leaks are repaired.
There are three large cooperages in the United States and two in Scotland. Some distilleries, mainly in Scotland and Ireland, have on-site cooperages.
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