Portugal produces about half the world output of commercial cork, and its exports over recent years have accounted for around 70 percent of world trade.
The cork oak (Quercus suber L.) finds its most suitable habitat in the western Mediterranean. An abundant and evenly distributed rainfall, short summer dry periods tempered by atmospheric humidity, very mild winters, clear skies and plenty of sunshine, very permeable, moist and deep siliceous soils -- these are the ideal conditions for the economic cultivation of the species. Such conditions are in fact found only in the Mediterranean zone, and, more particularly along the Atlantic shore.
The best quality cork is obtained from the province of Algarve and some parts of Alentejo that produced in the north of the country usually being inferior. As regards quantity, the central and southern zones rank foremost. Portuguese law prohibits stripping the trees more than once every nine years in order to protect the species.
The combination of such qualities in one substance led naturally to its industrial utilization, which dates back to very remote times. It only became important however after the invention of glass bottles, which opened up immense prospects for the sale of beverages and raised the problem of large-scale production of suitable stoppers. The stopper industry, which began in the Iberian Peninsula, has continued to expand to the furthest corners of the globe. Later a new type of stopper was devised - the American stopper or crown-cork - requiring a much smaller quantity of raw material than the ordinary stopper. This stopper, which consists of a metal or bakelite cap with a thin cork disc inside, has proved eminently satisfactory. The crown-cork began to be utilized on a large scale for bottles containing beer, mineral waters, fruit juices, pharmaceutical preparations, preserved foods, etc.
Among other non-producing countries, which have a fairly important cork, industry may be mentioned Argentina, Australia, Belgium, Brazil, Canada, Chile, Czechoslovakia, Denmark, Germany, Japan, Mexico, Netherlands, the Scandinavian countries, the United Kingdom, Uruguay, and the U.S.S.R.
Obviously, the producing countries play an important part in the industrial utilization of cork, and of these, Portugal, rightly occupies the foremost position. It has 500 factories, which employ about 20,000 workers, equipped with the latest machinery and utilizing the latest technological advances, enabling the industry to meet the demand for any product. This industry produces stoppers, discs, different types of floats, shoe soles, printing paper, cigarette tips, bath mats, table mats, hat bands, fishing rod handles, different kinds of packing. Cork wool is produced for cushions and mattresses and granulated cork employed chiefly as insulating material in ship-building, as a protective packing for fruit and eggs, and as tubing for plastic substances.