The STR barrel was developed and optimized for the aging of spirits by the late Dr. Jim Swan. The barrel arose from the need for more wood for single malt whiskey production and an abundance of wine barrels in Europe and America. Initially used for aging red wine.

S - step 1

3-5 mm is scraped from the inside of the oak surface of the barrel to remove some red wine residue that might otherwise give undesirable tannic and sulfurous notes (and possibly a home for unknown bacteria), but not to the point of removing all the wood stirred by the wine that might give desirable fruity notes.

T - step 2

The barrels are then toasted to break down the hemicellulose and lignins in the wood structure into wood sugars and other desirable flavor compounds that are soluble in alcohol.

R - step 3

Re-curing with an intense flame that caramelizes the wood sugars, causing the spirit to penetrate deeper into the staves, increasing the surface area of the inside of the barrel by creating shallow cracks, and acting as a built-in "carbon filtering system" that can clear up unwanted off-notes in just-distilled spirits.

First, the type of oak, American oak (Quercus Alba) or French oak of the European variety (Quercus Robur).

American oak has a tighter wood grain suitable for long-term aging, imparting notes of vanilla, caramel, citrus and coconut.French oak, with its coarser grain, gives the spirit faster access to the flavors within, but also more oxidation to the environment, and provides rich spicy and sometimes savory notes. Roasting temperature is also a factor, as it gives access to different flavors available in the oak: from woody to sweet, vanilla, toasty and nutty. Finally, there is the char level, graded from 1 to 4, which relates to the time exposed to intense heat: