There’s just something about natural cork. Newer technology may have its devotees, but there’s a good reason why good, old-fashioned cork is used to seal champagne bottles. Even if you set aside years of tradition and the satisfying “pop” you just can’t get with any other material, there are still plenty of benefits to traditional cork over synthetic materials and screw tops.
How It’s Made
Cork actually comes from the bark of the cork tree, which grows primarily in the montado forests of Portugal. Responsible harvesting makes cork a renewable resource, and small teams typically harvest the bark, allowing the trees to survive and the bark to regrow. The cork bark can usually be be harvested again every nine years.
Once harvested, the cork bark is cured, graded, sorted and then processed into natural cork disks and rods of agglomerate cork. The rods are sliced into the individual corks used to seal champagne bottles, with a natural cork disk affixed to each end.
The Natural Cork Difference
The key characteristic of natural cork that makes it perfect for sealing champagne bottles is its ability to expand. Pressure beverages like champagne – along with sparkling wines, ciders and some beers – are bottled at great pressure, and they require a seal that can prevent the escape of gases while at the same time maintaining the perfect gas pressure within the bottle. That’s where natural cork comes in.
When compressed, natural cork expands. The typical cork used to seal a champagne bottle has a diameter of 31 millimeters, but is compressed down to a diameter of 18 millimeters to fit into the bottle neck. Once in place, the cork naturally continues to expand, which allows it to keep constant pressure against the glass bottle neck. This pressure keeps gas from escaping, and makes natural cork the perfect stopper material for a champagne bottle.
That Tell-Tale Shape
You can tell a natural cork has done its job by its shape when you remove it from the bottle. You’ve probably noticed that corks come out of a champagne bottle with a recognizable mushroom shape, but they don’t go in that way. Corks are straight when they are inserted into the neck. The mushroom shape is the result of the lower half of the cork being compressed into the bottle neck, while the upper half continues to expand.
The Trouble With Synthetic Corks
Unlike natural cork, synthetic corks do not expand. They maintain a rigid shape, which can mean a loose fit and imperfect seal in some bottles. Ill-fitting corks can ruin a bottle of perfectly good wine or champagne.
Natural corks are also difficult to remove without a corkscrew, whereas natural corks are designed to be removed from a champagne bottle by hand. Just remember to never point the bottle at yourself or anybody else while you open it. Champagne bottles stopped with natural cork tend to open with a powerful “pop,” sometimes sending the cork flying. It’s a small price to pay for a perfect seal!