KRCB's Wine Beat: Behind the barrel

For centuries, this labor-intensive craft has been passed down through generations—and much of the work is still done by hand.
photo credit: Tina Caputo
Douglas Rennie, a master cooper, said the heat from the fire doesn't touch the
wood, it just heats the wood, and the natural sugars
that are left in the wood from the seasoning become caramelized.

Most people don’t think of wine barrels as having a “season.” But at the Seguin Moreau cooperage in Napa, barrel-makers are just moving into their busiest time of year. Barrel orders typically come in around February, and by April and May, the production room is buzzing. In a typical vintage, the facility makes 20,000 barrels for more than 800 wineries across North America.

Oak barrels play an important role in the winemaking process because they add subtle aromas, flavors and textures to the finished product. For centuries, this labor-intensive craft has been passed down through generations—and much of the work is still done by hand.

For Douglas Rennie, a master cooper at Seguin Moreau, coopering is a family tradition.

“ My father, grandfather and great-grandfather were all master coopers,” Rennie said. “I just followed in their footsteps and eventually found my way to Napa Valley.”

Rennie learned the trade through a four-year program in Scotland, making whiskey barrels, followed by another six months of training in France. Though modern machinery is used for some steps of the coopering process today, he learned the old-fashioned way.

“For the first two years of the apprenticeship, you're not allowed to use any machinery,” Rennie said. “Everything is done using traditional hand tools. It's an amazing way to learn your craft and keep the old traditional tools alive in the industry of coopering.”

To become a master cooper, like Rennie, you also have to learn how the wood is cut in the forest, how it’s air-dried or “seasoned,” and what happens during the fire-toasting process. Basically, you have to know everything about making barrels.

Each barrel starts with a set of 28 to 32 wooden slats. The assembly process begins when the cooper at the first work station stands the staves up to form a circular shape and adds metal rings at the top to hold them all together.

The cooper then tightens the rings–also known as hoops—with a hammer and a chisel-shaped tool called a hoop driver.

The partially formed barrel is placed over what’s called a “warming fire” for about 15 minutes to heat the staves enough to bend them without cracking. When the wood is ready, a machine bends the staves to complete the barrel shape, and another set of hoops goes on at the bottom.

Next, it’s time to toast the barrel over an open oak fire. Rennie said this is the most important step in coopering.

“The heat from the fire doesn't touch the wood, it just heats the wood,” Rennie said. “The natural sugars that are left in the wood from the seasoning, they become caramelized. It really softens the effect of the wood on the wine. If you were to put wine in a raw oak barrel that hadn't been toasted, it would completely overpower the fruit and spoil the wine.”

Once the barrel cools, a worker puts on the final galvanized steel rings and tightens them around the barrel. After cutting a groove into each end, he inserts the barrel heads and seals them in place with a flour and water paste.

To test the barrel for leaks, he sprays a few gallons of hot water into the bung hole at high pressure. If there are any weak spots, the water will shoot out. When the tester removes the wand from the barrel, it makes a satisfying whooshing sound.

After draining the water and removing the hoops, it’s time for sanding.

The sander smooths the surface and removes any discolorations. When it’s finished, the barrel looks like a beautifully crafted piece of furniture. The cooper then uses a nail gun to secure the hoops back into place, then finishes tapping in the nails by hand.

The final step is laser etching with the cooperage logo—and any other branding that the winemakers wants. The whole process takes about an hour, from start to finish.

“Today, modern machinery has really helped the cooper,” Rennie said “They've taken a lot of the physical labor out of the industry and coopers can do a lot more than just go home at the end of the day, exhausted.”

While barrel-making involves less hand labor today than it did in the time of Rennie’s great-grandfather, he says he still loves the tradition of coopering.

“For me, it’s the tradition—how old it is and how it's still used in modern day,” Rennie said. “We pay attention to every little detail, and that's what we love to do.”