There's a reason the screw cap hasn't dominated the wine stopper industry: Cork still kicks the ass of stamped aluminum for the good stuff-and not just for nostalgia's sake. This is what keeps our evening libations from turning sour.
Cork is an unbeatable bottle stopper. It's compressed by machines, jabbed by wine keys, and assaulted by liquids, only to bounce back, close up the gaps, and continue to keep leftover wine at bay.
Cork's been doing the same job well for thousands of years. Ceramics with cork tops were tucked into Egyptian tombs, and the Greeks shoved the spongy wood in containers filled with wine and olive oil. But it wasn't until Dom Pérignon-perhaps you've heard of him-developed the process for Champagne production in the 18th century that the cork stopper got its big boozy break. At the time, French sparkling wines were plugged by plain ol' wooden pegs wrapped with olive oil-soaked hemp. This setup blew. No, really. The gas in wine kept popping the slick stoppers out. Without a proper stopper, wine was losing its sparkle and the appeal of Champagne was falling flat. So as a way to seal his beverage-and ultimately his legacy—Pérignon started a series of experiments to find a better way. When he landed upon cork, it wasn't just the bubbly producers that appreciated a more perfect fitting: The entire wine industry ended up adopting it up as the stopple standard.
Cork performs extremely well under pressure. With some nudging, cork can compress to half its size, without bulging out the other side or increasing its length. Ok, so there are a lot of things that can do that if you push them hard enough, but the key here is cork's resilience. Cork's insides look like a honeycomb filled with gas-89.7 percent gas, in fact-which makes it both light and buoyant. And the cells that make up the honeycomb are insanely stretchy. So the cells can stand to be squeezed tight—like by, say, the skinny neck of a wine bottle.
But cork doesn't collapse under the abuse. Although the gas in the cells is compressed and loses volume, it is always pushing back, which allows it to seal cabernets and champagnes.
While stuck, liquid's constant lapping doesn't cause the cork to flinch. This wine stopping power is due to a coating made of a complex mixture of fatty acids and heavy organic alcohols called suberin inside the cork's cell walls. The suberin, plus tannins and a scarcity of albumenoids, leave it decay resistant and unfazed by moisture. In fact, the United Nations' Food and Agricultural Organization says that pieces of cork can stay submerged in liquid for centuries without rotting. Taken all together, these things make cork maybe the best seal in existence.
Here's another way cork gives other caps the finger: If you're keeping wine in a cellar for a long time, a little bit of air does a body good. The reason is that wine contains a little bit of sulfur dioxide. But "without oxygen, that sulfur disintegrates and creates a smell like a struck match," says Vance Rose of cork producer Amorim Cork America. You do not want to swirl that around in your cup and sniff it. Cork adds air naturally by releasing a wee bit of its stored gas, maybe 3-4 milligrams. Screw caps are either hermetically sealed, leaving bottles with a potential sulfur problem, or they've been engineered to allow a little outside air in. While that little bit of air is good for the sulfur, but not good if it's sucked from a wet cardboard or musty cellar. Cork's gas release doesn't come from the outside, so it doesn't smell.
This means that when it is time to pop the top, both wine and cork come out unscathed-the wine appropriately aged and the cork looking almost like it always did. Even after years of abuse, "the cork doesn't lose any integrity in its cell structure," explains Rose. "It goes right back to its original form." The cork has always maintained this fine form so your Malbec can, too.
Rachel Swaby is a freelance writer living in San Francisco. Check her out on Twitter.