A while ago we talked to you about the bottle manufacturing process and the importance of bottle design according to variety, wine type, and the brand image intended to be conveyed. There are many factors with an impact on the final quality of a wine: Not just the quality of the grapes (determined by the weather or vine health) and the winery’s production process, but also the materials used to produce the wine, such as the barrels, bottles, and closures.
In this post we’ll be looking at an essential element: the closures. We’re not going to distinguish which closure works better (cork, synthetic, screw cap, glass), since we already did that in another post published on this blog (link post tapones). What we are going to do is explain the manufacturing process and curiosities of cork closures, like we did with the barrels where the wines are aged (link post); where they come from and how they are made.
Functionality and history
The main function of cork stoppers is to preserve the properties of the wine over time and ensure that it develops correctly in the bottle. In short, corks prevent large amounts of oxygen from entering, which would damage the wine, and at the same time they act as a barrier against bacteria and mold. In ancient times, when wine was stored in amphorae, skins and tissues were used that had been treated beforehand with oils and fats, but these altered the quality of the wine. Around the 5th century BC, the Greeks began using corks as stoppers, and by the 17th century, with the proliferation of glass containers, corks had been adopted as the standard closure.
Portugal, the main producer
Spain’s neighbor is the world’s leading cork producer. It produces nearly 50% of the world’s production, while Spain contributes 25% of the total. The rest comes from southern Europe (France and Italy) and northern Africa (Algeria and Morocco). Cork is extracted from the bark of a variety of oak tree, Quercus suber, which has the ability to continuously regenerate its light, spongy bark. Trees must be at least 40 years old before the first extraction takes place, although it is recommended to wait another 15 years to achieve the ideal material for industrial uses.
Production process: from the cork oak to bottle
We’ll now outline the production process in a simple way, answering a series of questions:
How is cork made from the cork oak?
Manually. Electric saws are only used for the thickest parts. The bark is extracted from the trunk and the strongest branches, and this has to be done very carefully to avoid damaging the internal bark. If it is damaged, the tree will not regrow and will end up dying.
What’s the next step?
Drying. The planks of bark have to spend two or three days drying in the sun. Once dry, they are boiled to disinfect them and remove any impurities. This is when the cork swells and gets its definitive elasticity.
Selection and cutting
After resting for two or three weeks, the planks are graded into classes according to their quality, which is determined by their thickness, porosity, and appearance. The next step is cutting. A size is determined, normally a little wider than the length of the stopper that is going to be manufactured, and strips of this size are cut from the planks.
Punching and drying
Once the planks have been cut, it is time for the punching. This is done using a hollow drill bit, and the result is a cylindrical stopper. The desired size will depend on the type of stopper that is going to be made.
The resultant stopper is washed again to ensure does not contain any kind of impurity. Once clean, it is stamped with the usual markings we always see: vintage, logo, or any other information as desired. The printing is done with ink or fire, although the parts that are in contact with the wine are never marked with ink; heat is always used in this case.
Can the cork go into the bottle now?
Not yet. There’s still one final step to make it easier to insert the stopper in the bottle: treating the surface with paraffin or silicone to lubricate it. This also makes it easier to remove the stopper in future and improves the insulation. After bottling and closure, a capsule is added to most bottles of wine in order to better protect it. These capsules are usually plastic or a lead-tin alloy.
It is interesting to note that there are different kinds of cork closures. The nine used most frequently appear in this article from Vinopack.
As you can see, the cork stopper manufacturing process is pure craft and all the materials used are of natural origin. It is undoubtedly an essential element for the final quality of the wine and at the same time a key piece for conserving it.