The
story of an oak barrel ultimately begins with the tree from which the wood
came. A tree, like a grapevine, is affected by climate. In cold, dry climates, a
tree grows slowly, forming a narrow growth ring for that year. In wetter,
warmer climates, a tree grows more quickly and the growth ring is wider. The
widths of all the rings together become the wood's grain. A tree with mostly
wide rings is loosely grained; a tree with mostly narrow rings is tightly grained.
Because the wood inside a narrow
ring is more dense than that inside a wide ring, flavor is extracted from a narrow
ring more gradually. Winemakers generally prefer this, for in wines aged in
barrels made from narrow-ring, tight-grained oak, the oak character is usually
better integrated into the wine and the overall flavor of oak is more mellow. This
is why barrels made from trees that grow in the French forests of Troncais, Vosges,
and never are so sought after. All three forests are cool and dry and thus are
known for their narrow-ring, tight grained oaks. The forest of Troncais, in
particular, was planted in the late 1600s as a source of superior ship masts for
the French navy. Though American oak is not designated by the forest from which
it came, the best American oak also comes from cool places, such as Minnesota and
Iowa.
In addition to the species of oak
used (French or American), the manner in which a barrel is made significantly
affects the flavor of a wine. An oak tree is generally harvested when it is one
hundred years old or more. For centuries, the traditional European practice-still
used today by the best coopers-has been to hand split the oak into staves along
natural grain lines, then air-dry and season the staves by leaving them stacked
outdoors, exposed to sun and rain for two or three years. During this period
when the wood is unprotected, the harshest tannin is gradually leached out-ultimately
to the benefit of the wine.
The next step is to fit the
staves together as tightly as possible. An imperfect seam could result in a leaky
barrel or one that allows considerable oxygen to seep between the staves, oxidizing
and spoiling the wine. To form a barrel, a cooper using the traditional European
method heats the staves over an open fire to make them pliable enough to bend into
shape. This is still done entirely by hand with only the help of winches and
chains, as well as iron rings that must be hammered into place and act like belts
holding the staves together. It is backbreaking work. A top cooper working swiftly
can make just one barrel a day. The fire that helps bend the staves also
"toasts" them, caramelizing the wood's natural sugar into toasty,
spicy, vanilla flavors, which are ultimately imparted to the wine. Like breakfast
toast in a coffee shop, winemakers can order their barrels lightly, moderately,
or well-toasted, depending on the degree of toasty flavor they want to impart.
Second
method
In addition to this traditional
European method, there is a second method-one which, while sharply criticized
today, has been used extensively, especially in the past for American oak barrels.
In this method, the staves are quickly dried in a kiln rather than outdoors over
the course of years. Although expeditious, .kiln drying does not have the tannin-leaching
or seasoning effect that air drying has. As a result, kiln-dried barrels
tend to impart coarse flavors. This doesn't matter too much if the liquid Inside
Is bourbon, but If It's chardonnay, the result can taste terrible. The staves
for American barrels have usually been bent over steam rather than fire.
Barrels with steam-bent staves impart
a far less complex, less toasty character to wine than barrels made from fire-bent
staves.
(Think of the difference between boiled beef and
grilled beef.) The world of American oak barrel making is changing, however. Since
the mld-1990s, the best American oak barrels have been made according to the traditional
European method