From bark to bottle: a chronicle of the making of a cork stopper

A text message summons me to the outskirts of Santa Coloma de Farners at 6:15 a.m. There, Gil, the forestry technician, guides me to where a van with the group of cork harvesters is waiting. We greet each other briefly and continue in convoy along the road until we reach an inconspicuous turnoff. We turn onto a narrow track and begin to venture into the forest, through a kind of tunnel of trees and a dense undergrowth, which changes completely after a long climb. We leave the shady, damp areas behind; we are now at the top of the Castanyet stream, and we have been seeing cork oaks for some time. The airy, sun-drenched ridges of the Guilleries massif have favored their growth and spread for hundreds of years. Here, the cork oak reigns supreme.Quercus suber

When we arrive at the site, Gil shows the group the boundaries of the property where we're to work, to avoid mistakes that could lead to disputes with the owners. The geolocation device he used to mark the area is the most modern one that will be used today.

The technique for harvesting cork and the traditional tool, the axe, haven't changed in hundreds of years. The precision, experience, and care required to avoid damaging the tree are so important that mechanization is almost impossible.

The most experienced members of the group will be the first to start. Like someone testing a product, those with more experience can tell from the first axe strike whether the holm oak is ready to be stripped and whether the bark will come off easily. It will have been about fourteen years since the last time the cork was harvested. Wait this time for the cork to reach a thickness of 2.5 centimeters, which is the size needed to make stoppers.

The cork cam

The harvesting season begins in late May and ends in July, but this can vary depending on rainfall and temperature. The ideal time arrives when there's a change in the tree's growth cycle and sap flows through the trunk, making it easier to extract the outer layer of bark we call cork. Later, with the heat of midsummer, the bark re-sticks, becomes drier, and is very difficult to remove in good condition without damaging the tree.

The first two harvests from a tree yield low-quality cork, suitable only for making conglomerates for insulation, flooring, panels, and other uses, such as nativity scene decorations. Today, most of the trees on the estate we're walking on are around 50 years old, have gone through the first and second harvests, and are ready for the third, in which the cork reaches a quality suitable for the stopper industry.

They continue working, dividing up the trees. Some peel them in pairs, others individually. Kamal, who just turned 21, is the youngest in the group and always works with a partner. Although he's already been working in the forest for three seasons, he'll still have to wait a few years to become an expert like his cousin, who's been doing it for over ten years, or his uncle, who's been doing it for over twenty. Kamal was born in Sant Hilari Sacalm, the capital of the Guilleries region, and at home, his family always talked about forestry work related to cork oaks. However, a few years ago he moved to France with his parents. Returning to Catalonia every summer to work the cork harvest is becoming a tradition.

A few precise, transverse blows with an axe at the top of the trunk limit the height from which the bark will be extracted. Next, vertical cuts are made down to the base of the trunk, and then the cork can be pryed off, trying to remove it whole or in two pieces, without breaking. Each whole piece is called a "panna." When making the axe blows, care must be taken to ensure the depth is just right to avoid wounding the tree. Any wound poses a danger, a potential entry point for infections, and can also lead to malformed growth that would affect the next layer of cork and reduce its quality.

The group stops to have a bite to eat, drink water, and sit for a while. While they lie down, in a mechanical gesture, they take the opportunity to sharpen the axe blade before returning to work.

When the day is over, the cork planks will be stacked at the side of the road to facilitate loading when a transporter comes later to pick them up and take them to the factory.

The cork factory

In Cassà de la Selva, near the Gavarres mountains, another historic cork oak forest area just a few kilometers from Les Guilleries, I visit one of the town's cork stopper manufacturing plants. In the past, almost every family in this area was involved in the cork industry, and it's said that one in three of the world's cork stoppers are made between Cassà de la Selva and Palafrugell. This is, of course, an exaggeration, but according to the Catalan Cork Institute, 2 billion cork stoppers are manufactured annually throughout Catalonia, destined for every corner of the globe.

The stopper is the highest quality cork product and, therefore, requires the most stringent controls. At the Costa Quer company, they work exclusively with local cork: they don't go more than sixty kilometers away to source it. In Catalonia, cork oak trees grow more slowly than in other warmer parts of the Mediterranean, resulting in denser cork that lasts much longer once in the bottle and in contact with the wine. This quality requirement is so important that only 30% of the cork entering the factory will be used for this purpose. The rest, everything rejected as defective or failing to meet quality standards, will be used to make other, less demanding products, such as agglomerates for insulation, decoration, or architecture.

Before processing begins, the corks must be left to dry outdoors in full sun for a year. Afterward, the cork must be reactivated: it is boiled to hydrate it and make it more workable, as well as to clean it of dirt, bacteria, and fungi. Once it has cooled, it will be ready.

I enter a large, airy room. At the far end, a window backlights a machine being operated by one of the workers. It cuts the cork planks into strips and simultaneously fills the space with a subtle cork scent that will accompany me throughout the factory. This work is semi-automatic; one of the workers cuts the slices into strips and feeds them through the machine that perforates them into stoppers. It's a job that requires more precision than it might seem because the pieces are irregular and must be inserted in the best position to use the maximum amount of cork. On the other side of the machine, where the operator is located, the stoppers come out via a ramp and fill a large container.

From this first rudimentary, rough, and poorly defined cork in terms of edges and size, to the final, polished cork with the appropriate shape and size, chosen and selected from hundreds of corks, it must undergo microbiological, physical, and visual controls that are essential to guarantee.

In the process between machines, following a 3D control circuit and laser technology to obtain the final size, the cork will undergo manual and visual inspections where qualified operators play the key role. Using a sample cork as a reference piece, they compare each one individually with the help of a set of mirrors to facilitate observation from all possible angles. This allows them to separate the unsuitable corks from those that pass to the next filter, the last step before final validation: the olfactory test. It may be surprising, but this will ultimately determine if the cork is optimal for sealing a bottle of wine and guarantee that its aroma will not alter its flavor or any other sense. This test is performed with the cork slightly heated, between 60 and 70 degrees Celsius, to properly capture the aroma it emits, and this is done not by any sophisticated machine but by a trained nose.

More than a year after ceasing to shelter an oak tree in the Guilleries mountains, that piece of cork, selected, treated, and transformed with extreme care, will reach the world of wineries to seal bottles until the ritual gesture of the corkscrew releases the aromas of the wine.