Dec. 1, 1864.] THE TECHNOLOGIST. 



CORK AND ITS USES. 195 



upon these cork slabs is caused by the application of heat at an open 

 fire, after the steeping, for the purpose of contracting the porea. The 

 pieces are afterwards bound up in bales, in which form they appear in 

 the market. In removing the cork from its paternal trunk, care has to 

 be taken not to injure the inner bark next the wood, else it would affect 

 the second crop of bark, and perhaps injure the tree. This operation of 

 stripping the bark, if dexterously and carefully performed, has, as we 

 have already said, no detrimental effect, either upon the growth of the 

 tree or the rapid formation of the new bark ; but, on the contrary, the 

 tree is said to grow more hardy and vigorously. The first crop of bark 

 is usually taken when the tree is about twenty-five or thirty years old, 

 but the crop is of less value than that of any succeeding gathering, as it 

 is harder, very uneven, and more full of holes. The second gathering, 

 however, which is in about eight or ten years after the first, is still of 

 an inferior quality. The third crop, collected in about eight years after 

 the second, is usually the first marketable cork — that is, the first crop 

 that is fit for cutting into bottle-corks. When the trees have attained to 

 this age, so that three crops have been taken off, they usually yield a 

 supply of good cork about every seven or eight years ; and its quality 

 improves, as well as the quantity enlarging, at each successive gathering. 

 The season chosen for the cork harvest is usually the months of July 

 or August. 



It will be seen by the foregoing that the quality, and consequently 

 the commercial value, of cork is materially affected by soil, length of 

 time allowed in growing, and also of care in collecting. There is as 

 much difference existing in the quality of cork as in most other articles 

 of daily use. The finest kind should be compact and firm, but at the 

 same time not hard, of an even texture or grain, and of a slightly 

 pinkish tint. This kind of cork is generally selected by wine-merchants 

 for bottle-corks ; while the coarser kind, which is always more porous, 

 full of small holes, and perhaps punctured by insects, serves for bungs 

 for casks and for the various other applications to which cork is put in 

 a cheap form. When cork is required to be thick, it is usually found 

 coarse, as it must be allowed a longer period of growth to promote 

 its thickness. The charring or singeing process to which this kind of 

 bark is frequently subjected, for the purpose of filling up the pores and 

 making it impervious to fluids, has also a detrimental effect, as it secretes 

 an empyreumatic oil, which is given off and frequently taken up by the 

 liquids it confines ; but there is no doubt that care is taken in the selec- 

 tion of these corks, and methods adopted for the prevention of this 

 chemical contamination, as much as possible. This operation of charring, 

 to which all cork was formerly subjected for the purposes we have just 

 mentioned, has been partially succeeded of late by that of boiling the 

 cork and afterwards scraping the surface. This is said to improve 

 rather than to deteriorate the cork, in being more effectual in filling up 

 the pores. 



