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KNOW YOUR CORKS

Updated: Sep 21, 2020


You would be surprised how many people in the Philippines ignore that bark corks are not the only method used by wine producers to seal their bottles. Actually, many types of wine closures have been created in the last few decades with the purpose of optimizing wine’s preservation and marketing.

Romans used to experiment with rags, wax and cork in order to seal their wine amphorae. Since then, pieces of bark of different sizes - harvested from oak trees - have been the best natural seals for wine barrels in Italy and the rest of Europe, until the 16th Century. In the 17th Century, glass blowers started to manufacture bottles with narrow necks making airtight storage possible and cork stoppers proved to be the best closures.


In the 20th Century technology advancement helped to develop new types of stoppers which today, basically, only screw cap and synthetic cork are consistently challenging bark cork’s supremacy in world’s vineyards. Comparing the three always ignites debates among wine lovers on which type of cork is better than the other. In this outline, however, I will also mention a fourth type of closure which somehow keeps coming back: the vintage crown cap.

BARK CORK. Natural bark cork is the oldest type of wine closure, specifically selected and improved through time because of its many qualities. It is single-pieced, waterproof, elastic and microporous thus able to shield wine from external agents, protecting its flavour and texture while - at the same time - allowing a small amount of oxygen to interact with wine. This “breathing” is essential to wine’s aging process. However, defective and/or low quality bark cork might confer to wine a moldy off odor called TCA, (tricloroanisole). TCA happens when microorganisms dwelling in the natural bark react negatively in the presence of other compounds such as chlorine. However, Amorim, the Portuguese world leading producer of bark cork, has created and launched a few years back “NDTech” bark corks specifically screened with gas chromatography for TCA and therefore sold with a guarantee against it.

Bark cork is a natural, renewable and sustainable resource. The bark is harvested by hand, and in Portugal (where 49.6% of the world's bark cork is produced), the cork oak trees are prohibited by law from being cut down. Quality bark corks price cost may range from 50.00 to 120.00 Php.




There are other types of natural or semi-natural corks: multi-piece, agglomerated and colmated cork, which are corks assembled with scraps and/or chips of bark glued together. These corks are manufactured for low-end wines to be consumed within two-three years from the bottling. Being much cheaper than the single-piece cork, at around 38.00 Php, they somehow seem to serve the purpose.


SYNTHETIC CORK. Created a few decades ago, it has aficionados in the New World wine industries where it is used on a large scale. They are realized by thermoplastic polymers that ensure a perfect compression when the cork is inserted into the bottle. This type of cork is also used with young wines (to be consumed within a couple of years).

Synthetic corks are sterile, cannot be attacked by molds, they are cheap (around 15.00 Php) and the wine bottles can be stored in vertical position. In contrast, they open like bark cork and they don’t let wine breathe naturally while, being petroleum based, they may add a chemical smell to the wine.

SCREW CAP. Since its creation in the 1950s, this aluminum cap has been associated with unrefined and cheap wines but nowadays there are a lot of wineries that have adopted it. It’s the most common closure used in the New World Wine Regions, specially Australia and New Zealand, with both Countries pioneering its employment since 1990s.


Having a waterproof coverage on the interior side as seal, the screw pitch avoids gas exchange, so screw cap seals tighter than natural cork, keeps out the air, it’s less expensive (around 12.00 Php), easy to open and close with a simple twist. However, because the wine can’t “breathe”, there is a risk of sulfides imparting off aromas among others. For its qualities it is considered practical in terms of storage and transport, good as a short term wine stopper for fruit forward reds and most whites that don’t require aging. Lately its use is being extended to premium wines as well.


Innovation has permitted the manufacture of screw caps with calculated levels of oxygen ingress over time. However, it remains to be calculated how much oxygen and over how much time each grape and style of wine would need, which is almost an impossible task for wine-makers to sort out.

On the other hand, innovation has also lead to the creation of a screw-bark cork called Helix, by the same Amorim company above, designed to screw in and out the bottle.


CROWN CAP. Patented back in the 19th Century, crown corks today are mainly used as closures for carbonated drinks, particularly bottled beers and sodas, because it can hold high pressures. One time use and inexpensive (from 3.00 to 6.00 Php), its interior side has an elastic coverage that ensures airtight closing. Safe and efficient, crown caps are still used in Italy and other Mediterranean countries as inexpensive table wine bottles stoppers performing surprisingly well as far as wine preservation is concerned. It is now regarded as a valid alternative to screw cap for younger wines.

Experiments have been and are still being carried on at wineries all over the world with the intent of establishing which closure is more suitable from all the different point of views. Basically, samples of same styles of wines produced, of the same vintage, are being corked with different types of stoppers and left for periods of time awaiting to be opened for comparative evaluation.


In the year 2000 PlumpJack Winery, Napa Valley (CA), bottled half of its 1997 Reserve Cabernet Sauvignon with corks and the other half with screw caps: PlumpJack supplied samples of both the cork-sealed and the screw-capped wine to researchers in UC Davis’s Enology and Viticulture Program for evaluation. However the results, even after blind tastings, were essentially inconclusive.

Time will tell us if screw cap, synthetic and crown corks will be as effective for wine as the cork bark has proved to be for centuries, delivering us a wide range of perfectly aged wines of the highest quality. Perhaps, bark cork and its cork alternatives could coexist side by side as it is already happening in many wineries in the Old and New World where, for instance, natural corks are used for young red wines, synthetic for whites and screw caps for rose’.


No matter what, bark cork will always remain a timeless resource, essential part of the old rituals and traditions of wine drinking. The natural cork evokes ancient cultures, craftsmanship and refined taste: a priceless added value. Furthermore it is so far the only natural, sustainable and biodegradable stopper ever not to mention aesthetically warm and appealing.


The ceremonial act of opening a bottle of wine totally loses its meaning when the stopper is synthetic, screw or crown cap. Beyond any doubts, the world's legendary wines sealed with bark cork are not going to switch to screw caps, or else, anytime soon.

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