The Craft of the Master Cooper

Coopering—the art of barrel building—is an ancient trade dating back a couple thousand years, and since then little has changed in the process. But today, only a few dozen Master Coopers practice around the world. Ramiro Herrera, Master Cooper for Caldwell Vineyard in Napa, is one of those remaining few.

Herrera discovered a passion for the trade after getting hired at the cooperage Seguin Moreau when he was a teen. Within three years, they had sent him to France to begin training to become a Master Cooper. “There were 40 of us in the beginning, and only two of us made it through the training. People were quitting within the first three or four days,” says Herrera of the training, which lasts four years.

“There are no power tools allowed—everything is done by hand. They want you to learn the artisan way. It’s hard work—very hard work.”

Herrera stuck it out and learned to love the trade, a process he recounts in our September/October 2016 issue. Here, he offers a behind-the-scenes look at the work of a Master Cooper.

Sourcing the Wood
One of the most important stages of barrel building takes place not in the warehouse but in the woods. Just as a winemaker carefully considers the soil content of a vineyard, so too is a cooper concerned with the terroir of the forest where wood is sourced. “I used to build barrels from four types of oak: American Oak, French Oak, European Oak and Russian Oak. But French Oak seems to be the best to use, especially when making Bordeaux-style wines,” says Herrera. “We buy our French oak from one particular forest in France where the soil is great and the flavors are unique.”

After the wood is carefully selected, taking into consideration tree shape, growing conditions, fineness of the grain and tannin content, it is cut into staves and stored outside for several years to season. This process, exposing the wooden staves to the open air and elements, naturally ages the wood, mellowing its flavors and allowing some of the bitter tannins to leach out.

Building the Barrel
Herrera estimates that it takes him about 11 hours to build a barrel by hand. And while the fundamentals of barrel building are more or less the same as they were in Roman times, today machinery can assist in many steps of the process. While this increases efficiency, it still takes a cooper’s trained eye and touch to ensure all the pieces come together to form a perfect, watertight seal, and Herrera often prefers to use his hand tools for detailed work. “These days you use machinery for just about everything,” says Herrera. “But there’s a lot that you still do by hand, like repairing a stave if it breaks. You have to change the stave and use an axe to shape it.”

With speed and precision, the staves are placed inside the first set of metal hoops, in a process called mise en rose, or “raising the barrel.” Applied heat and moisture coerce the boards into their arched shape as they are winched into place to set the final hoops.

Toasting
One of the most important steps occurs after the barrel has already been built—toasting the inside. The level of toast will determine many of the final flavors imparted to the wine or spirit like vanilla, caramel, toasted bread and nuts. For wines, toast levels vary from light to dark depending on what the winemaker is hoping to achieve. A fire is built inside the barrel and allowed to gradually toast the wood. “On a normal wine barrel, it would take about 35 minutes with a low fire. You’re allowing the toast to penetrate about a quarter-inch into the wood,” says Herrera. “By contrast, for whiskey it would just take 45 seconds; you crank the fire all the way up and just burn the surface. The inside of the barrel looks like an alligator’s skin. You burn the hell out of them.” For the Master Cooper, this step could never be achieved by a machine. “You have to do it by hand. You have to touch and smell the wood to get it right.”