I’ve written about wood before. The previous article talked in detail about casks because they are important to so many different kinds of maturing alcoholic beverages that it is useful to see the big picture: Where do casks come from and how are they used? You might think that a cask is a cask is a cask, but that’s not true at all. At least in the Scotch whisky business, distillers pay very close attention to their cask supplies, and even have job titles involving “wood management.” Casks are not an afterthought.

We saw that many ex-Bourbon barrels end up in Scotland — but they aren’t all alike. In order to maintain a steady supply of barrels of the same type and with the same flavor characteristics, various Scotch distillers have long-term arrangements with Bourbon producers — to the point where a multi-national corporation that owns a Scotch distillery might acquire a Bourbon distillery just so they have more direct control over the sourcing of the wood used in the barrels that will age their Scotch. There are specialist cooperages that are tied to certain Bourbon distilleries that use particular shapes, toast levels, residual moisture levels, etc.

As with much of the Scotch production process, details matter. To deliver a consistent product, year after year, decade after decade, it’s critical to keep track of all these details. The production of the new make spirit takes only weeks, from malting to mashing to distillation (months if you include growing the barley), whereas the aging takes years or decades. You had better get this part right or your careful production of the spirit will come to naught.

The occupation of cooper has been one of the most important for many centuries. Prior to the invention of glass, wooden vessels (barrels) were the preferred way to store liquids. Other than earthenware containers, they were probably the only practical way to store liquids. There are many kinds of barrel designs, not all of which are water-tight. A water-tight barrel is the pinnacle of the cooper’s art.

To say that the cooper is one of the most important jobs involved in the production of whisky is not much of an overstatement. But the whisk(e)y business is not the only business for which barrels are important: Cask-conditioned ale is aged in wood barrels. Port and Sherry are, too. And of course, Bourbon whiskey. And wine, rum and many other types of distilled spirits and fermented beverages.

Because of American law, Bourbon must be aged in new oak barrels. These cannot be reused. So the Bourbon industry generates a prodigious amount of used barrels. I have read recently due to the recent strong growth in the popularity of Bourbon whiskey, the demand for American oak suitable for Bourbon barrels has effectively reached parity with the available supply. Basically, as fast as the right kind of oak trees mature, they are cut down for barrels. This is a staggering fact!

The structural surplus of American oak Bourbon barrels has had a noticeable effect on the style of Scotch whisky. 100 years ago, Scotch was primarily stored and aged in European oak. Since the end of Prohibition in the US, the “waste” barrels from Bourbon production were available, and these American oak barrels found their way to Scotland where they were increasingly used for the Scotch whisky industry’s storage needs. Mark Reynier, CEO of Bruichladdich, wrote extensively on this topic in a blog comment on the What Does John Know blog (the “John” in the title is John Hansell, editor/publisher of Malt Advocate magazine).

A cask (barrel) is born near where it will be first used. If it’s from European oak, it’s probably used for wine or Sherry or Port. If it’s American oak, odds are it will become a Bourbon barrel. Sherry barrels are called “butts;” Port barrels are called “pipes.” Once used, they may be re-used for their original purpose, but many find their way to Scotland (or Japan, or any other whisky-producing region) to be used in aging or finishing of whisky.

Once used for whisky aging, these barrels are classified by the number of times they have been used. For instance, first-fill Sherry casks, second-fill, and so on. A barrel that has been used multiple times may still be quite useful. A second- or third-fill cask may be desirable precisely because it’s not presenting an overabundance of Sherry or Port notes. Even Bourbon barrels may be valuable in a second-fill applications. It depends on the degree to which the barrel has retained its ability to impart wood notes to the contents. Eventually, the barrel will lose its “flavor” and it will no longer be useful. This may well take many decades.

So we have established that casks are used for a mini-ecosystem wherein barrels are used first for one application, then used again. At first glance, Scotch seems to be the end of the road for the barrels. Whether they started as Bourbon barrels, Sherry butts or Port pipes, they all seem to eventually end up in Scotland (or in the production of whisk(e)y). I have never heard of Scotch being aged in a beer barrel, though interestingly there are new beers that have been at least partially aged in Scotch barrels.

The micro-distillation revolution in the United States is stretching the boundaries of how casks are used. It’s a very exciting time to be in the whisk(e)y business. You can stay up to date with my list of American whisk(e)y producers on the Whisky2.0 blog. For a few off the top of my head, there are: Charbay, Tuthilltown, Stranahans, Old Potrero, and St. George. There are many others.