Definition: Corking and muzzling champagne

The role of the cork is absolutely essential, as it is the guardian of the wine's quality. The cork must be easy to insert and fit snugly to ensure a perfect seal. It must be easy to remove, but with a certain amount of resistance. Once removed from the bottle, the cork should take the shape of a mushroom. To combine all these qualities, champagne houses use cork as the sole material for making these corks. It takes nearly forty-five years before the first layer of bark that can be used to make corks can be removed from a cork oak tree. That's thirty-five years before removing the first bark, which is unusable because it is too cracked, and then another ten years for the replacement bark to reach sufficient thickness. This is true for all corks. From there, champagne corks differ because the very nature of this wine imposes very strict constraints.

It must withstand a pressure of around 5 to 6 kg/cm². This is almost three times the average pressure of a car tyre. To ensure this resistance, their initial diameter must be 31 mm, which is 13 mm more than the diameter of the inner neck of the bottle! And that is the big problem. Perforating cork bark to create cylinders of this diameter is virtually impossible. It would take an extremely long time for the bark to become thick enough. However, the longer the cork ages on the tree, the more it loses quality and the greater the risk of cracks forming. All these reasons made it necessary to develop an original process. To make this 31 mm diameter cylinder, several pieces of cork are crushed (the particle size is precisely controlled) and agglomerated with a very special glue, the development of which led to the definitive adoption of the agglomerated cork. This glue had to be resistant to moisture, compression and lateral torsion! At one end of the cylinder, the end that will be in contact with the wine, two discs of natural cork, selected with the utmost care, with a diameter of 31 mm and a height of 4 mm, are superimposed and glued together. The number and dimensions of these discs are specially designed to ensure that the weight is evenly distributed throughout the cork. The most surprising thing is that the manufacture of these corks continues to be the subject of research and improvement. Five years ago, they were soaked in hot water for nearly an hour so that they could be inserted into the bottles. Today, food-grade silicone is used. This material has the characteristic of promoting slippage during dynamic movement and becoming sticky when static. This is doubly clever, as it increases the capping rate while also reducing gas or liquid loss by creating a surface of adhesion between the glass and the cork. The cork stopper must not be more than 48 mm high, more than 31 mm in diameter or have a breaking force of more than 25 kg. It consists of an upper part made of agglomerated cork granules, the "handle", and, for the lower part in contact with the wine (or "mirror"), 1, 2 or 3 6 mm discs of natural, solid and flexible cork.

The cork must bear the name "Champagne" around the edge of the part inserted into the neck of the bottle and, where applicable, the vintage. Often, either the name of the producer or a small five-pointed star with a long tail appears below, to celebrate the "wine of the comet", after the comet seen in 1811 during a particularly abundant harvest, or to celebrate Christmas, a time particularly conducive to the consumption of sparkling Champagne wines. As cork is a natural product, each cork is unique, but it can also be the source of a fault that can be found in any wine: cork taint. Nothing seems to be able to protect certain vintages from this, except for testing and approving batches after statistically checking them. However, technology now offers hope for the total eradication of this problem. The Cortex company has recently begun researching what it calls a "sensory deviation preservative". This is a silicone piece that would be installed on the side of the cork in contact with the wine, preventing both cork taint and leaking bottles. Still in the testing phase, this project offers great hope. Until recent years, silicone materials did not offer the specific advantages of cork, which, although airtight, allows micro-oxygenation, which is essential for the development of wine. Today, there are new polyethylene materials that perfectly meet this requirement and are therefore qualitatively equivalent to cork. To soften suberin, the heat-sensitive resinous material in cork, soaking tanks are gradually being replaced by systems that use hot air or microwave ovens to heat and soften the cork: this is known as "dry corking". The softened corks are put in place by compression (reducing the diameter to approximately 17 mm), pushed into the neck of the bottle to half their length, then crushed into a mushroom shape to receive the wire cage. The wire cage consists of a metal "cage" made of wire and a metal plate bearing the name of the producer. Placed on the cork, the plate is tightened around it to prevent it from being ejected under pressure. The plates, which are often decorated, thus serve to promote the brand image of the Maisons and protect the cork from the muselet. The muselet is distributed and applied automatically by a pneumatic machine, the "museleteuse".

See muselet.

Finally, it should be noted that the shape of the champagne cork before use is completely cylindrical and has a large diameter. From bottom to top, it consists of a^top-quality cork plate that will be in contact with the wine, followed by a large cylinder of agglomerated cork that is much more resistant and will withstand the pressure and stress to which it will be subjected when the bottle is opened.

Once compressed by the corker and inserted into the neck of the bottle, then held in place by the plate and the wire cage, it will take the shape of a mushroom with a stem that springs back when uncorked for a young champagne. Springing back means that it regains some of its original shape.