What is an STR cask?

The three operations run in that order. The inner surface of the staves is shaved back, the fresh oak beneath is toasted, and the innermost layer is then recharred. What comes out is a cask with fresh, heat-treated oak on the inside and whatever the wine left deeper in the staves.

Coopers already had an answer for a tired cask, which was to remove the spent charred layer and char it again, reaching fresh wood beneath. STR does something different, and to a different cask: it works on a barrel that has held wine rather than whisky, and it toasts the fresh oak before charring it, so the wood is worked in two stages rather than one.

Jim Swan started the work in 2008, with experienced coopers. He had been asking what a cask does to spirit since the 1970s, and from 1986 he had been studying the wood itself and the practices of the cooperages. By 2008 he had a clear idea of what a young whisky needs from a barrel, and of how the wood might be worked to provide it.

There are several STR recipes, and each gives a different result, so a distillery specifies what it wants rather than ordering a standard article.

A distillery starting from nothing has no stock laid down and no back catalogue to fall back on, so its first casks have to earn their place. A used wine cask given a second working life is affordable in a way that first fill bourbon wood is not.