Glass bottle closures from corks to bottle caps are small things to which we do not give much thought. But their design and deployment over the last century elegantly illustrate the competitive, messy and often unpredictable process of human design in action.
Let us start with the mechanical requirements for sealing glass bottles. The most demanding of these are sodas, sparkling wines and champagnes that require a closure that holds under the pressure of dissolved gases that bubble forth when the beverage is opened. Wire cages hold corks onto the rim of champagne bottles to resist this pressure. It can be a surprise when the mushroom-shaped cork comes out of the bottle, never to go back in because it expands so dramatically. A red or white wine does not need to resist the considerable pressure of dissolved gases, so wine corks do the job without the wire cage, and with less cork material.
Now any wine snob can tell you that corked wine is preferable to wine under a screw cap. So following that advice we have been turning up our collective noses to wines with screw caps for a few decades. The opinion is that wine tastes better under cork compared to screw caps. But is this true under a controlled experiment? One American wine producer decided to do the experiment. The slide deck summarizing the findings of Hogue Cellars Ltd. with some very nice graphs and statistics can be found here at www.twistopenhogue.com.
(Now you may notice the wine company shares my surname. I admit the only reason I came across this bit of research was due to the coincidence, but I assure you I get no freebies from Hogue Cellars Ltd. The research itself is what interests me.)
Hogue Cellars Ltd. reports that 2% of the bottles they seal with natural cork are ruined by the displeasing taste of cork taint. Cork taint is, most simply put, spoilage due to cork failure. So the assumption that all wine under cork tastes better fails for 2% of the bottles. Yet the wine snob has a choreographed defense mechanism that guards them against cork taint, and allows them to mentally disregard this problem.
Let me explain the familiar ritual. The sommelier’s careful pouring of each bottle of wine for initial tasting starts by pouring a small amount of wine into one glass, and the taster is offered the cork to inspect. That first careful sip allows the taster to detect the taste of cork taint and if it is present, the customer can send it back for another bottle. The ritual is repeated in fine restaurants around the world. The odds are small that any individual will find cork-taint. 98 times out of 100, the ritual reverts to the more enjoyable purpose, of assessing the quality of the wine, its nose and its flavor components. And as this is more frequent, it has become the accepted motivation for the ritual amongst aspiring and established wine snobs. Those who are unaware of cork taint blame the taste defect on the wine manufacturer, not the cork material.
Now a winemaker has the benefit of a much larger statistical survey of the quality of its products than any individual customer. Hogue Cellars Ltd. knew that the economic loss of cork taint was spoiling an unacceptable fraction of their wine production. The loss of a couple of bottles out of every hundred they sealed is a failure rate that is simply never tolerated in any other mass-produced food or beverage product. So they looked for alternative bottle closure designs.
Hogue Cellars Ltd. tested a panel of metal and artificial cork-like closures over several years of storage and then let expert taste testers be the judge. They did not design any of the closures they tested, they were making a selection by statistics and the scientific method. The fraction of natural cork closures that have no taint won the taste test. Their selection criteria sought an efficient closure alternative that best maintained the taste compared to the untainted cork-sealed bottles. They tested tin, aluminum, and steel varieties from a number of manufacturers. Their research confirms the wine snob opinion that some closures, including tin and aluminum, will dramatically alter the taste of wine over time. The winner was a steel cap with a special polymer coating that provides the gas permeable qualities of cork and allows the wine to age while preventing it from being spoiled by metallic components.
While the research at Hogue Cellars Ltd. is of 2011 vintage, the battle to remove cork spoilage and inefficiency has been raging for over a century in other bottled products. Today we live in a world where wine is the last product to be going through the transition. The gas permeable nature of cork has been difficult to design into a suitable competitor to natural cork. Yet it is the power of selection by the consumer and our ritual that keeps the cork around, even when it is so inefficient in production. Let us next consider the case of the classic soda bottle cap.
Here is a photo from a small collection of soda bottle caps I have, where you can see the underside lining of the leftmost example is made using composite or pressed cork. The rightmost examples have polymer linings. These caps are from the 1970s, and I remember most of them from my boyhood. You may be surprised to learn that cork remained a part of bottle caps as the bottle-cap liner for so long after the invention of what was called the “Crown Cork” by William Painter in 1891 (U.S. Patent 468,226 ). The second example in the photo has a disk shaped wafer of plastic overtop the cork keeping the cork away from the contents, but allowing it to seal along the rim of the bottle. This plastic wafer no doubt improved the shelf life and efficiency of the seal and prevented spoilage of the beverage by the cork.
I remember all of these cap designs coexisting at the same time. Some searching on Google Patents shows that nearly every one of these small changes in design has an accompanying patent. I remember getting bad bottles of soda with cork bottle cap liners, and spitting out the first gulp in disgust. But to my boyhood delight, by scraping off the plastic bottle cap linings with my thumbnail, the printing underneath the liner revealed contests and promotions. Bingo games or a free bottle of soda. Of the polymer linings, you can see printing on one of them. It is a small change in design and even this small change was patented in 1966 (U.S. Patent 3,257,021) including the new purpose of promotion.
The design of better bottle caps and seals by trial-and-error is obvious in the photo, and the changes in the U.S. Patent office tell the story quite well from first-hand accounts. But as a boy, I preferred a bottle with a contest, and the cap-liner promotions made certain bottles with such liners more attractive to me. So the incremental human design improvement from the cork to plastic liner also changed the marketing of the product.
Change came gradually to the market, as cork and polymer liners were still in competition in the 1970s. The promotions added a speculative dimension of selection that was not related to product quality or cost. That is to say you might win something. Or you might not. The soda maker could not print a contest piece on composite cork because it would shatter when you removed it. The cork-lined bottle cap is now extinct from production, but the wine cork is still with us. Wine manufacturers could easily change the attraction of the screw-capped wine bottle in the same way, by employing the steel cap for a promotion or contest. A promotion might kill off the wine cork faster than a stack of graphs and research. However alcohol advertising and promotions are strictly regulated and many jurisdictions have laws against contest promotions of booze as it might encourage alcoholism. So another selective pressure that keeps the cork in the bottle is, perhaps not so strangely, the preservation of human health.
The selective pressures that allow the wine cork and the screw cap to co-exist today are a messy combination of agricultural, economic, cultural and legal challenges. There are natural limits to the production of cork that makes it difficult to sustain mass production. Customers have strong opinions about wine taste under cork and have developed cultural rituals to preserve the myth that all wine under cork is better-tasting, when 2% of it is quite awful stuff. Legal hurdles prevent wineries from promoting the screw-cap to make the product more attractive compared to the corked product. There is no apparent way to separate the promotion of a wine with a certain design of bottle closure from the promotion of the alcohol inside. There seems no way to tip the balance by human design, that favors the screw-cap over the cork.
So without a means to make the screw-cap more attractive than cork, wine manufacturers are resorting to the scientific method in the hope that human reason can prevail over human ritual and bring closure to the cork era. Don't be surprised when a sommelier twists open your next bottle of wine and asks you, "Would you care for some graphs with your wine?" while pouring your first sip.
