All About the Champagne Cork

How Champagne is Corked featured photo

When we think of champagne and cork we think, best friends forever, duh. But why? What brought these two together and what’s the secret to their long-lasting relationship? As with much of the romance and mystique surrounding champagne, there’s quite a bit of science on standby for explanation. Let’s have at it.

The Origins of Natural Cork

The Origins of Natural Cork featured photo

Natural cork is the bark of Quercus suber (cork oak) a species of tree native to the Mediterranean (western Africa and southern Europe) that is drought tolerant and requires little input. These trees grow to around sixty-five feet tall and can live over four hundred years but will only be harvested to around two hundred years old. The bark, being regenerative, can be harvested with little invasion or threat to the health of the tree. Cork trees are highly protected for cultural, ecological and economic reasons alike, and cannot be cut down without permission from national governments .

The first harvest occurs when the trees are about twenty-five years old, but the quality of the bark at this stage is not optimum for wine cork production so it is used for the other industrial materials such as flooring, insulation and decorative items. Subsequent harvests are suitable for wine corks and occur every nine to eleven years. A cork tree is usually harvested twelve to sixteen times in its lifetime.

How Are Corks Made? 

​​three wine corks

Enclosure solutions for champagne and the development of the champagne cork have a history as lengthy as the beverage itself. While cork had been utilized by wine making cultures since ancient times, it was not rediscovered as a viable solution for containing champagne bubbles until the 17th century. (Dom Perignon is often credited with the invention of both champagne and its cork but this has widely been disproven by historians and authorities in the field.) And even then, there was still the problem of corks blowing off in the cellars causing injury to workers and exploding other bottles. The following century the muselet — the wire cap that is secured over the head of the cork and top of the bottle — was developed which aided in solving this problem. 

Both the developments of the champagne cork and muselet were dependent upon a standard champagne bottle shape. Needless to say, these elements which make champagne stable and safe in the bottle have undergone constant tweaking throughout history and, to this day, continue to be researched and innovated.

Contemporary champagne corks start out looking much like regular wine corks, with the exception that they are 50% wider in diameter (this is to account for the extra pressure needed between the cork and the neck of the bottle to withstand the pressure of carbon dioxide in the champagne). This diameter is too wide to be harvested from the cork tree in a single cut, so the solution is to grind the bark and reform the bits into an agglomerate cork body (properly termed manche) using food grade adhesive that is water, pressure and pull resistant. To the bottom of the cork body are attached two virgin-cut natural cork discs that will be in contact with the wine. These discs form the part of the cork called the miroir.

Cork production is heavily regulated by the governing body of the region called the Comité Champagne. Any cork manufacturers new to the market must submit their products for lab testing and approval before they can be used. Additionally, there are cork requirements of the champagne producers themselves; corks of their champagnes must show the name of the appellation around the middle portion that is inside the neck of the bottle (vintage is sometimes required, too), and the bottom of the cork must contain the producer’s stamp.

How Champagne is Corked

champagne cork with muselet

In order for champagne corks to be fitted inside their bottles they must be heavily compressed in the jaws of a corking machine. They are inserted into the neck of the bottle with about one-third of the top of the cork remaining outside of the glass. This external part of the cork is what the wire cage, the muselet, is fitted over. Being the incredibly elastic material that it is, the cork expands to form the hermetic seal that prevents our beloved champagne bubbles from escaping. 

Why are Champagne Corks Mushroom-Shaped?

The internal pressure of the bottle on the cork is relieved when the cork is removed. This results in the cork flaring when the pressure equalizes and that forms the “stem” of its mushroom shape. The “cap” results from the top of the cork having molded to the shape of the wire cage. Cork bark loses its elasticity over time, so the longer a cork remains in a bottle of champagne, the less pronounced a mushroom shape there will be. In fact, after about a decade, the internal part of the cork may be permanently compressed to just the diameter of the neck of the bottle.

What About Synthetic and Other Enclosures?

10 types of cork stoppers

While there have been significant advancements in the technology of synthetic wine corks, natural corks are still the best and only permitted for champagne production. This is because of cork bark’s properties of elasticity and expansion being able to form the right kind of seal for the conditions of champagne.

You may, however, encounter other kinds of enclosures used for other types of sparkling wine and this should not make you doubt the quality of the wine or the efficacy of the stopper! There are multiple methods of making sparkling wine and each process results in a different degree of bottle pressure and various aging techniques that dictate the type of enclosure needed. Just do a little research and experiment trying different styles with different enclosures. In the booming market of wine, it’s beneficial for the regeneration of the cork forests for there to be other materials, many eco-friendly, available for wine bottling. For the time being though (and let’s be honest, probably forever), champagne will remain, shall we say, traditionelle.