Wine barrels are a common scene in winery photos. Some people know they like or don’t like an oaky Chardonnay or Cabernet Sauvignon.  Most serious wine drinkers know there is a difference in flavor between French & American oak even if they can’t say what it is or why it is.  Let’s see if we can address some of those issues & especially how barrels are made at one French barrel maker.

Last year I had the opportunity to visit Tonnellerie Morlier in Bordeaux.  I was with a group of 6 sommeliers & other wine professionals that the Bordeaux Wine Council & Wines of Germany brought over to take a different look at the wines of Europe.  Part of the idea was to show us more white wines in Bordeaux & more red wines in Germany.  As part of our Bordeaux visit, we stopped in at Tonnellerie Morlier which is in Saint-Estèphe, part of the Medoc region about 50 km from the city of Bordeaux.

At Tonnellerie Morlier we were greeted by Denis Morlier a former carpenter turned barrel maker (which still seems like carpentry to me). They have been making barrels since 1991. There are 15 barrel makers along the Gironde river and another 16 in Cognac.  There are a total of 60 barrel producers in France.

What kind of wood do they use for wine barrels?

Almost all wine barrels are made with white oak. Red oak is too porous. There are 3 species of oak that are used for wine barrels.  Two of them are native to Europe & one is native to America.  What makes white oak so good for barrels to age liquids is something called tyloses.  Tyloses grow in the xylem vessels of wood & when the plant is stressed, they fall from the sides of the cells & block that tissue to prevent further damage to the plant.  So basically, they block the distribution of liquid (sorry for the super abbreviated explanation).  White oak has a lot of these tyloses & American white oak (Quercus alba) has the most, much more than European White Oak (Quercus sessiliflora & Quercus robur). Because American oak has more tyloses, it can be sawed into shape without increasing the risk of leaking.  European oak can’t be sawed & must be split to follow the tubes & then bent so the tubes are parallel to the staves to prevent leakage.  This is one important reason American oak barrels are less expensive than French oak barrels. You get more barrels from the same amount of American oak than you do from European oak.  One estimate I have read says that only 20 to 25% of a European oak can be used for barrel making, while 50% of an American oak is suitable for barrel making.  That’s a huge difference & helps explain why French oak barrels are in the $1,000 range versus American oak barrels at around $550.

One other key difference between the European & American species is the space between the grains.  The European oak has tighter grains, which means they deliver slower, subtler, & smoother results.  American oak has a wider grain & delivers quicker results with greater tannin extraction & sometimes bolder flavors.  Some of the difference may be due to cooler growing regions in Europe meaning less growth each year & less distance between the growth rings.  It doesn’t account for all the difference though.  There are also some flavor differences between American oak & the 2 species of European oak.  These aren’t hard & fast guidelines but should be enough to help you tell the difference when tasting wine.  American oak shows vanilla, coconut, sweet spice, & dill.  It contains more vanillin compounds that the other two.  French oak leans toward dark chocolate, roasted coffee, cinnamon, clove, & savory spices.  Hungarian/Eastern European oak sits somewhere in between with higher vanilla notes than French oak, roasted coffee, and dark chocolate. Quercus Robur is more robust (hence the name).  It has bigger tannins & gives less elegant flavors to wine.  It is used for Cognac more than for wine.  Quercus Petrea has lower tannins & a rich aroma.  It is the most suited for wine.  The two European varieties grow in forests together, particularly in France & have crossbred with many hybrids.  Many coopers use a combination.  It is also possible to make barrels that blend various species of oak into one barrel.

Acquiring the wood for the barrels

Denis gave us some background on the process used to acquire the wood used for these extraordinary barrels.  It turns out that you can’t just run over to Home Depot & grab some two by fours.

There are five main forests that provide wood for wine barrels in France, Nevers, Tronçais, Allier, Limousin and Vosges.  These names are often stamped into the barrels since some believe that oak from different forests imparts different flavors to the wine. Potential buyers go through the forest & tag the trees that they want.  These trees will be at least 100 years old & frequently over 120 years old.  Potential buyers are allowed to measure the trees & even to bore into them up to 30cm to determine how straight the grains are.  Then there is a bidding process.  The forests are 50% privately owned & 50% government owned. The sale of over 80 per cent of the forest wood is administered by the National Forestry Office (ONF). In September and October wood auctions are held across France. This is a carefully controlled process to ensure sustainability of this renewable resource.  The auctions used to start with a top bid based on what they hoped to achieve.  Now they work like a standard auction & start low & end high.

Morlier buys their oak after it has been cut into boards for staves.  Then it is time to mature the wood.

Maturing the wood

The wood staves are stacked outside for 2-3 years to season.  Sometimes piles are rearranged so that everything gets an even amount of sun, but generally they are just left alone to sit all of that time.  Obviously, a goal of letting the wood sit is so that it can dry out, but that doesn’t take that long & sometimes the stacks may get rained on or snowed on.  So, what’s the point of them sitting for years?  The flavors of the oak become more subtle & nuanced as the wood ages.  The longer the wood is dried, the less toasty the wine aged in it becomes.  This is true at all levels of toasting the oak.  There are some wines that might benefit from oak barrels made with staves that saw longer aging & some that might do well with oak that was aged for a shorter time.   If you are making a nuanced wine with subtle flavors, maybe a barrel made from well-aged staves is best.  If you are making a big & bold Syrah where you want to accent the smoked meaty notes, a barrel made with newer staves might be perfect.  Another factor is the amount of new oak you want to use on the wine & the length of time you want the wine to spend in the barrel.  If it is a small amount of new oak for a short time & you want maximum impact, barrels made with less aged oak might be best.  Making a high-end Bordeaux rouge with 2 years in 1/3 new oak probably calls for barrels made with well-aged staves.  This is an area where something that seems pretty straightforward is actually pretty complex for wine makers who know what they are doing.

Production process

After the staves are properly aged, they are sanded roughly & made slightly curved.  The tips are sanded down to be narrower than the middle.

It takes 30 staves to make a barrel.  Staves may be of small, medium, or large width, but the same size is always on the opposite side of the barrel for balance.

The fire used to bend the wooden staves is made from the scrap oak. The first time the barrels are exposed to fire the barrel is wet & warm to bend the staves & get the correct form.  The second time is for toasting the barrel.  The time spent toasting the barrel ranges from 15 minutes to 2 hours, so the size of the fire & length of time are both important.  Denis didn’t mention this, but it is also possible to use steam to bend the barrels rather than fire.  This is done for some barrels intended for white wine since it adds the smallest amount of flavor to the wine.

For the tops of the barrels, pieces of reed are inserted between the wood staves creating a better, natural seal.  A mixture of flour & water is used in the groove at the top of the barrel to check for water tightness.

After the barrel is completed, it is checked with 200 liters of boiling water.  The barrel is moved around to check for leaks.  Some barrel makers use high pressure air to test. If one stave leaks, they can replace it, but they have to repeat almost every step in the process.  You can’t just slap in a new stave & call it good.

Once the barrel is finished & tested, nice rings are put on it and the barrel is sanded to a final finish.  For this, they use a big spinning sander that can sand the top or the bottom of the barrel at once.

More information on toasting barrels

I mentioned above that the second use of fire with the barrels is for toasting the barrels.  I feel like they decided to call it toasting because scorching or burning didn’t sound as enticing.

The process of heating the oak with fire as they do at Tonnellerie Morlier causes chemical changes in the structure of the wood.  The length & intensity of the exposure to the fire changes the oak (& the finished wine) in different ways.  There are three main levels of toast, although certainly different coopers can use different processes.  For most of the wine world, the three levels are as follows…

Light toast: Just slightly darkens the wood.  Can provide a scent of vanilla & caramel notes.

Medium toast: This is the familiar brown toned wood we see most often.  This is where you get roasted nuts (particularly on barrel fermented wines), baked bread, more vanilla, coffee, & generally stronger notes associated with the various oak species.

Heavy toast: Darker wood, stronger coffee notes, sometimes deeper chocolate notes, toasted bread, & generally much more intense heavy flavor notes. The higher the toast, the more the compounds associated with vanillin (furfural & 5-methylfurfural) decrease & the more they are replaced with smoky compounds ((guaiacol, 4-methylguaiacol) & spicy compounds (eugenol, isoeugenol, 4-methylguaiacol).

Many finished wines will be a blend of wine that was in barrels with different toast levels.  There is generally a target taste & texture & often that is an optimal blend of new & old barrels with varying degrees of toast. For wine makers at my skill level there is a lot of trial & error involved.  Great wine makers can really dial this in & know beforehand exactly what they need to get their desired results.

Final thoughts

At Tonnellerie Morlier, three people can make 6 225-liter barrels a day.  Each barrel gets a unique ID so that it can be identified later.

The standard in France for high quality wine production is to use 1/3 new barrels, 1/3 2^nd use, & 1/3 3^rd use barrels.  After the 3^rd use the barrels are generally sold.

Denis says that customers buy his barrels because of how he makes them.  He doesn’t keep any stock on hand.  Every barrel is custom made!  Some wineries give him a thick book of instructions for what they want.  Others know how he works & just expect the best.  He makes barrels for many different wineries including a First Growth Château.

If you want to become a barrel maker, be prepared to work & study.  There are three schools in France where you can learn the trade.  You must attend two years of school & then spend two-three years as an apprentice before you are considered a real cooper.