I've been to nearly 50 distilleries of all kinds of spirits, but a few weeks ago was my first visit to a real cooperage- finally! Vicard Tonnelleries is a 6th generation cooperage near Cognac in France, where they produce 60,000 French, Eastern European, and American oak barrels each year.
American oak? Yes indeed. They buy trees in the US, let them dry a bit (I believe they said they're split into staves in the US), ship them to France and make barrels out of them there. Then some of them are shipped back to the US and other countries for use.
Speaking of drying barrels, American oak staves only have to dry for two years, while French oak dries for I believe four years. At this cooperage all staves are air-seasoned (left to dry outdoors) while in the US many are dried in kilns.
American oak barrels were described as aromatic and useful in short aging of spirits, whereas French oak barrels have more tannins, add structure to wine and spirits, and are better for long aging. French oak barrels are more expensive, but that's also in part because they're cut differently than American oak barrels. French oak staves are cut so that only 30 percent of the log is used, whereas American oak staves use the opposite- 70 percent.
This huge cooperage is very automated, yet dozens of workers end up working on every barrel. The cooperage has machines and staging areas for splitting logs, further splitting, making staves, assembling barrels, making lids, installing lids, toasting barrels, testing, labeling, and I'm sure many other processes. During and between each one, a worker is on hand to do physical tasks as simple as moving barrels and as complicated as fitting a lid.
When a barrel is assembled by hand, staves are placed into a circle with one or two hoops around the bottom, then the top staves are pulled closer together by fitting a cable around the top staves, heating the inside of the barrel staves with fire, and cooling the outside with water while pulling the cable tight. Here though, the half-assembled barrel goes into a giant steam machine and the cable is tightened automatically. When it comes out, the cooper fits the top hoop and tightens it on.
They also make some gigantic barrels of the sort you'd use for blending, fermenting, and storage. I think one would make an awesome cottage for the backyard, but then again I'm basically 12 years old and want to build a fort.