At Pisoni, we’ve been paying particularly close attention to the Soberanes Chardonnay we released this spring. This wine was fermented and aged in a Foudre, a type of cask that is not conventionally used for barreling California chardonnay. All of our Chardonnay is barrel-aged. Traditionally, we have elected to use small, sixty-gallon barrels for this wine for both the Santa Lucia Highlands blend (which ages for ten months) and our Soberanes Chardonnay (which ages for fifteen months). Two years ago, we made a significant change when we decided to age the Soberanes (a wine particularly high in acidity and structure) in Foudre. Together with its large size, the elliptical rather than cylindrical shape of this barrel allows the wine to age more slowly.

Cooperage is one of the areas of winemaking I find most magical. The size and shape of the barrel, the source and “toast” level of the wood—all these factors subtly but profoundly play their part in the finished wine. Winemakers use a great variety of barrels, from the smaller pièce and barrique to the moderately-sized Puncheon to the large Foudre. These sizes were originally established for practicality—transportation needs, storage requirements, cellar space, wood integrity—as well as to serve the palate. These days, we think only of which barrels will give us the best quality when we begin upon the challenging task of matching the vintage with the vessel. Because we make wine in small quantities at Pisoni, it’s critical that we choose the proper barrel before bottling. Aging a great wine in an excellent barrel improves the wine; choose the wrong barrel for the vintage, however, and even the best wine can be destroyed.

One of the ways in which barreling changes wine has to do with the surface area available—the aging is caused by the indirect result of oxygen entering the wine through the barrel. Obviously, the aging process changes depending upon how much wood is in contact with the wine. As a rule of thumb, consider that a large bottle of wine will age longer than a small bottle, since the same amount of air must pass through the cork. Emile Peynaud states this rather simply in Knowing and Making Wine: “Young wine develops more rapidly in small volume.”

Flavor and tannin compounds resident in the surface of the wood are transferred to the wine as it ages. Too much of these compounds, or the wrong kind, will destroy a wine. Determine just the right amount of contact, however, and you enhance the wine. The goal is never simply to “taste oak.” Instead, a judicious amount of oak can help channel the fruit by lifting its aromas and adding structure.

Surface area changes when the size or shape of the barrel changes. Using a different barrel size or shape can drastically change the “ratio” of surface area to the volume of wine. A single barrel of sixty gallons has a surface area of 51 inches per gallon of wine. If you double the number of gallons—more precisely, if you use a puncheon, which weighs in at 132 gallons, the surface area reduces to 39 square inches per gallon of wine. That second figure means you have a vessel of wine aging in your cellar with far less surface interaction with the wood. Here, too, the winemaker must achieve balance. See the infographic at the end of this post which generalizes some of these concepts and ratios.

When people discuss cooperage, they often focus upon wood. But oxygen also informs aging. Take the surface area to volume ratios above and add another factor—not the barrel itself, but the air resident in it. Oxygen is a serious contributor to a wine’s evolution. Small amounts of oxygen pass through the barrel, the joints, and the bunghole (Vivas, 1999). If you use a larger barrel, like the Foudre, the wine receives proportionately less oxygen than it would if it were casked in a barrique or a puncheon, since there is a lower ratio of surface area to wine volume. Equally important is the age of the wood. If you choose a neutral barrel (for example, one that is ten years old), you will have little left in the way of wood tannin or flavor compounds. But a neutral barrel such as this still impacts the wine very intensely, in part because of the specific amount of oxygen that passes through the vessel into the wine. Like flavor compounds, the amount of oxygen that passes through a barrel changes as the cask ages. An older barrel can have as little as 25% – 50% of the amount of oxygen ingress as a new barrel (Vivas, 1997).

Choosing the right amount of wood is a matter of precision and balance. We’re confident that closely monitoring our Chardonnay as it ages in Foudre will produce a wine of great complexity and longevity. Winemaking is an evolutionary process, at once an art and a science. We’re very much looking forward to sharing our Soberanes Vineyard Chardonnay.