CORK 



CORK is the outer layer of bark of 

 an evergreen species of oak. The 

 tree is cultivated principally in Portugal 

 and Spain. When the tree is about 15 or 

 17 years old the first stripping takes 

 place, but this first crop is too coarse in 

 texture to be of use except in tanneries 

 or for rough purposes. The second 

 stripping, obtained 8 or 10 years later, is 

 also too coarse for finer uses than for 

 floats for nets. With each stripping the 

 quality improves and is continued at in- 

 tervals of 8 years until the tree is 150 

 years old. 



During the last several years the 

 French have begun to exploit the natural 

 cork of Algeria, where they have found 

 about 1,000,000 acres occupied by the 

 cork oak. The largest forests are in 

 northeastern Algeria and contain some 

 trees with a circumference of more than 

 30 feet. Messrs Thomas H. Kearney 

 and Thomas H. Means, of the U. S. De- 

 partment of Agriculture, give the follow- 

 ing description of the cork oak industry : 



Only natural forests are exploited in 

 Algeria, no attempt ever having been 

 made to establish artificial plantations (as 

 in Spain and Portugal). 



In bringing a forest of cork oak into 

 condition for exploitation the first step is 

 to remove the layer of old or "male" 

 cork which forms under natural condi- 

 tions. This operation, which requires 

 considerable skill, is performed in the 

 spring when the sap is beginning to rise. 

 The subsequent yield depends largely upon 

 the way in which this work of "demas- 

 clage" is done. It is advisable to put 

 back into place the layer thus removed, 



fastening it around the trunk by means 

 of wire and leaving it there for about two 

 years ; otherwise the trees are very liable 

 to injury from dry, hot winds and from 

 fire. Wrapping the trees in this way also 

 prevents a second development of the 

 worthless male cork. 



The new cork which now begins to 

 form is alone of commercial value. It is 

 deposited at the rate of from 0.04 to 0.12 

 inch annually, and the first harvest is 

 taken when the layer of cork has reached 

 a thickness of about 1 inch. Thereafter 

 the cork is removed every eight or ten 

 years, the later crops yielding a better 

 product than the earlier ones. The ex- 

 pense of each harvest from a single tree 

 is about 2 cents. 



Individual trees differ greatly in the 

 rate at which cork is formed. As a rule, 

 the best product is that which develops 

 most slowly. Rapidly growing cork is 

 more abundantly veined with loose tissue, 

 which diminishes its value. The cork is 

 sometimes seriously injured on the tree 

 by the ravages of ants, which build gal- 

 leries in it. The tree has also other insect 

 enemies. 



The cork, when cut, rolls up into tubes 

 of the size of the trunk from which it 

 was taken. It is first pressed out into 

 sheets, then boiled, and finally the crust 

 of bark is removed by scraping. Boiling 

 increases the bulk by about one-fifth and 

 renders the cork more elastic. 



An acre of cork oak in full production 

 yields a net annual revenue of about $2. 

 The product from a single tree is worth 

 from 4 to 10 cents a year after all ex- 

 penses are deducted. 



