Frequently Asked Questions

  1. Do you cut down the Cork Tree to harvest corks?
  2.  Is the world running out of cork?
  3. Does Natural Cork allow wine to breathe?
  4. What is the accurate estimate of the rate of Cork Taint?
  5. Are Natural Corks being replaced with alternatives?

Do you cut down the Cork Tree to harvest corks?

No, the Cork Trees are not cut down, or harmed in any way.

Harvesting cork is the operation of removing bark from the tree during spring or summer. This is the time of year that the tree is engaged in rapid growth. The tender, newly generated cork cells break away from the cambium easily and without damage. 

It takes from nine to ten years for the new bark to grow to sufficient thickness for the next harvest. Studies show that cork trees that are regularly harvested live longer than trees that are not. The average cork tree enjoys an expected lifespan of over 200 years. One example of a particularly robust specimen is see with the Whistler Tree.

Harvesting cork is an excellent example of a natural and sustainable resource. That is why the cork industry is supported by numerous environmental groups such as the World Wildlife Fund, the Rain Forest Alliance, and the Forest Stewardship Council.


 Is the world running out of cork?

There is plenty of cork available, the forest is healthy and expanding.

Portugal's cork forests are a carefully protected resource. The paramount importance of the cork industry to the Portuguese economy had led to strict regulation of the growth and management of cork trees. For more information
With the help of reforestation programs funded by the European Union and the Portuguese Government, the area of cork forest under cultivation in Portugal is growing by about four per cent a year. Today, new trees are being planted at twice the rate at which old trees are dying.
Contrary to a common misconception, it is estimated there is currently sufficient harvestable cork in Portugal's cork forests to meet market demand for more than 100 years.
The World Wildlife Fund considers the cork forest to be a vital buffer against desertification in the Mediteranean Region. They have identified the current growth of the cork forest and the social value of its harvesting are directly related to the continued health of the cork industry.


Does Natural Cork allow wine to breathe?

No, natural cork allows a limited amount of oxygen to enter the wine from within the compressed cork.  Outside air does not permeate into the wine with a properly stored cork finished bottle.

Oxygen ingress with natural corks is primarily a result of diffusion.  A typical 44mm cork contains an estimated at 3.5ml of oxygen.  When the cork is compressed the internal air pressure increases to between 6 and 9 atmospheres.  This establishes a pressure imbalance that is solved by the gradual equalization of gasses between cork and headspace.

The exchange of gasses explains why studies of oxygen ingress show that bottles with natural cork “pick up” a small amount of oxygen over the first 6-9 months of aging.  After that, oxygen ingress is no longer significant (the referenced study ran for 36 months). 

Variations in oxygen diffusion between corks appear in the first six months of storage and likely reflect differences in cellular structures.  After the initial diffusion period, additional variation was not observed.


What is an accurate estimate of the rate of Cork Taint?


CQC inspection records place the rate of cork taint at less than 1%.

This estimate is derived from results of TCA screening for all incoming cork shipments received by Cork Quality Council Members. The screening process employs GC/MS chemical detection method applied to samples of 50-cork wine soaks. CQC Members test an average of over 20,000 samples per year. Measurements of TCA are reported as low as 1 part per trillion (ppt). 

Since initiating this screening protocol in 2001, CQC members have seen an 81% decline in TCA levels. Incoming cork lots are flagged when one or more samples reveal TCA levels exceeding 1.5ppt. Independent studies have shown that cork lots within this range produce taint in bottled wines at a rate well below 1%. In the study – three lots were tested within the range of acceptance by the CQC. There were 180 bottles sampled after 20 months with only one bottle (0.6%) having TCA above the CQC reportable level of 1.0ppt. That sample was 1.6ppt – well below the sensory threshold for TCA.

These conclusions are amplified by two wine industry experts who have reviewed the results of large tasting events. Dr. Christian Butzke, of Purdue University and President of the American Society of Enology and Viticulture, examined the results from 3,240 entries in the 2008 Indy International Wine Tasting. He found less than 1% were affected by cork taint as expressed by the common definition of contamination with TCA. The results led Dr. Butzke to state that “TCA is no longer a major problem for the American wine industry.” 

In November of 2009, Lisa Airey – a leading American wine educator – reported the results of the annual convention of the French Wine Society. Noting that no more than 4 out of 500 (0.8%) wines exhibited any sign of cork taint, she declared that "The numbers are pretty impressive...Obviously, we are seeing a very positive upswing in the soundness of natural cork." 


Are Natural Corks being replaced with alternatives?

Cork stoppers are the most popular closure with U.S. consumers and wineries.

Alternative closures have been tested extensively over the past twenty years, and they have become very popular in some markets, but cork is the closure of choice for U.S. consumers and most wineries.
Numerous surveys* show that cork closures are preferred by U.S. consumers, and are associated with higher quality wines. In one recent article appearing in Decanter, the rise on Nobilo Sauvignon Blanc to be the number one US brand in this varietal was attributed to the decision to bottle with a cork closure.
In a recent survey of 229 U.S. wineries story, natural cork was the highest ranking closure in the categories of product performance, consumer acceptance, bottling line performance, environmental impact. Cork trailed the alternatives in price and was ranked slightly below screwcaps in ease of removal. The participating wineries showed that their use of cork products had increased in the five year period that the survey covered.
Further evidence of corks popularity is seen in the performance of the Top 50 US wine brands, where brands primarily bottled under cork show higher sales growth than those brands bottled with alternative packaging. This gap is more pronounced at the higher end of the pricing spectrum. In the most recent period, for Top 50 wine brands with an average price greater than $6.00 per bottle - brands finished with cork closures posted annual sales growth of 9.3% compared to a decline of -6.9% for alternative packages.