What happens to the wood?

[cowdery]

We talk a lot about aging and about the affect of wood on whiskey, but let's approach it a different way. What is the affect of whiskey on wood? I'm interested in what happens to new wood (i.e., bourbon aging) as well as what happens to old wood (i.e., scotch aging). Do changes that occur in the wood over time, either naturally or through its contact with whiskey, alter the way it ages whiskey later in the barrel's life?

For example, we know bourbon penetrates the wood and dissolves partially carmelized sugars and other substances such as lignin. What percentage of these substances are extracted from the wood after one year, five years, ten years, etc., and how does this affect the wood? Are any substances completely depleted in the early years, so they would be present in bourbon but never in scotch? Are there other substances that only become available later in the barrel's life?

No speculation please, just facts.

[Gillman]

Well, one effect of whiskey on wood indubitably is to leach out its tannins. Tannins, an amazing natural preservative, keep wood intact and free from bacterial and other degradation. As tannin leaves wood, the wood starts, quite literally, to rot. This is why some whiskey is musty. This why, too, artificial cycling, especially if effected too quickly, may prematurely deplete wood of its tannin and spoil the aging whiskey - even whiskey just 4 or 5 years old. My source: Charlie Thomasson, old-time, practical distiller of Willett's, writing in the 1960's.

Gary

[cas]

I don't have any special insights, just a related question. I suspect barrels have been made from oak for it's structural integrity. But have any other woods ever been used to age whiskey - maple or ash, for example?

Craig

[Gillman]

Sappy woods are not suitable, even oak needs to be dried properly to avoid sap leaching into the whiskey (or too much). As early as 1810 or so white oak had been identified as the best wood for whiskey. Samuel M'Harry's book of that era lists white oak first, then black oak, then a series of other woods in declining preference.

Gary

[tdelling]

There's also the issue of porosity... many woods just can't hold water,
and are only suitable for "dry cooperage". White oak is one those
that doesn't leak like a sieve.

I have heard stories of a couple small European (Scandanavian?) distilleries
using woods other than white oak, but can't recall the details. In my
recollection, they're the only ones in the world doing it these days.

Tim Dellinger

[tdelling]

It looks like you've been bitten by the bug that gives otherwise
rational people an intense curiousity concerning the complex and mysterious
chemistry of whiskey! Just a few warnings:
1) It gets more and more interesting the deeper you look.
2) People will accuse you of ruining the magic and trying to synthesize
whiskey from chemicals and taking the fun out of it. Little do they know
that exactly the opposite is true.

Anyway, those are some big questions you've asked, and I'll have to have a
look through my "library" a bit to give you referenced answers.

In the meantime, a few tidbits that I've been meaning to dig deeper into,
but haven't yet:

1) Musical instrument makers will tell you that wood will actually degrade
*in air*, and will measurably lose weight. They also have a few things to
say about this phenomenon's effect on the sound of the guitar/violin/etc.
So it doesn't take liquid to change wood!

2) In Scotland, they will sometimes "rejuvinate" barrels by scraping out
the insides, often with flailing chains that spin around and smash into the
staves of the barrel. They also re-toast sometimes. Both of these practices
are to "fix" barrels that "used up". All of this gives clues as to what makes
a barrel useful.

3) Oh, and a warning: whiskey people are traditional, and they also don't
spend gobs of money on detailed research... and the stuff you do find is
more likely to be Scotch than boubon. I've found myself spilling
over into wine barrel research, cognac aging, etc., as well.

Tim Dellinger

[Hedmans Brorsa]

I have heard stories of a couple small European (Scandanavian?) distilleries
using woods other than white oak, but can't recall the details. In my
recollection, they're the only ones in the world doing it these days.

Tim,

The Mackmyra distillery in Sweden, who has yet to offer a commercial product, matures some of their stock in new Swedish oak. They claim to be the first one ever to do so.

Unfortunately, I am not a botanical man so I cannot claim to possess any intimate knowledge of Swedish oak but I´ve always regarded it as white. I could be dead wrong on this one, though.

There is also a new distillery in Lahti in southwestern Finland. I know nothing about their production schemes, I´m afraid, but I have never heard of any "exotic" barrels being used.

[dougdog]

Headmans,

The botanical "Quercus" or "Oak" family is a large one. There is almost positively a "white oak" that would only/predominantly grow in Sweden and the locals would likely find that tree when searching for something unusual to use in a distillery wood/barrel/cask program. I'd bet if you contacted the distillery and asked around a bit you could get the exact "species/variety" name.

Oaks are so varietal/varied because they cross hybridize quite easily. This would lend to the concept that "local wood" would have its' own unique influence on the spirit being barreled. There is, after all, American oak, French oak, Spanish oak and Scottish oak being widely used in barrel/cask programs around the world...why not Swedish oak?

Now, if we could just get someone in the bourbon industry to lay up some white dog in some of those barrels for a taste in a few years...let's say...Sampler at the Gazebo 2010 as a 4 year old. (Then in 2020 as a 14 year old)

Certainly there would be annual progress samples distributed for "research/documentary" purposes, right?


dougdog

[cowdery]

Buffalo Trace has laid up some bourbon in French oak, and shared tastes of it widely although no product has been released. When a group of us were given a taste a couple of years ago, we all knew we were tasting something different but couldn't put our finger on it. Then Marvin Franz said, "this isn't American wood." And he was right.

Great taster, that Marvin.

[JeffRenner]

The botanical "Quercus" or "Oak" family is a large one. There is almost positively a "white oak" that would only/predominantly grow in Sweden and the locals would likely find that tree when searching for something unusual to use in a distillery wood/barrel/cask program. I'd bet if you contacted the distillery and asked around a bit you could get the exact "species/variety" name.

Here is a good source of information on oak used in cooperage. The link there on French oak has this pertinent information:

The most common oak in France, as throughout the rest of Europe, is the Quercus robur species (also known by the designation of Quercus pedunculata and Quercus rubra) which flourishes in a variety of growing conditions. Another important, though less common species of oak in French forests is Quercus petraea (also known as Quercus sessiliflora, Quercus sessiflora and Quercus sessilis), which has a tighter grain. ... A tighter grain not only means a less porous wood, which ensures a watertight barrel, but releases oak flavor to the wine more slowly.

The flavor of wines fermented or aged in European oak is different from that of American oaked wines. I am not sure if I could pick it out in whiskey as Chuck notes that Marvin did, but the oak flavor we are familiar with in bourbon is typical of less expensive American Chardonnays (and some more expensive ones as well, to be sure). European oak is less vanilla-ish.

Jeff