Gilbert Erwin Stecher

“ First I project on the screen a microscopic section of the wood of the cork tree. It is taken in a horizontal plane, and I ask you to notice the diversity of the structure and especially the presence of large tubes or pipes. I next exhibit a section taken in the same plane of the corky portion of the bark. You see the whole substance is made up of minute many-sided cells about 1⁄750 of an inch in diameter and about twice as long, the long way being disposed radically to the trunk. The walls of the cells are extremely thin and yet they are wonderfully impervious to liquids. ”

“ The Capgrand-Mothe system, which, as known, consists of dressing the trunk with the same cork just removed, and leaving it so dressed for a couple of months, has not met with approval, as being impracticable on a large scale. After the stripping, the phellogen, the seat of the growing processes, undertakes at once the formation of a new covering of finer texture, and each year this, the real skin, with its life-giving sap, forms two layers of cells, one within, increasing the diameter of the trunk, the other without, adding thickness to the sheathing of bark. ”

“ All plants are built up of minute cells of various forms and dimensions. Their walls or sides are composed chiefly of a substance called cellulose, frequently associated with lignine, or woody matter, and with cork, which last is a nitrogenous substance found in many portions of plants, but is especially developed in the outer cork of exogenous trees, that is, belonging to an order, the stems of which grow by the addition of layers of fresh cellulose tissue outside the woody part and inside the bark. ”

“ I have now projected on the screen the feeble light emerging from the crossed Nicol. I introduce the microscopic preparation of cork cells between them, and you see the crystals glowing with many colored lights on a dark ground. Minute though these cells are, they are very numerous and hard, and it is partly to them that is due the extraordinary rapidity with which cork blunts the cutting instruments used in shaping it. ”

“ The waste is rapidly assuming great importance and to this the newer entrant in the business is turning all his energy. The doctrine of conservation and utilization has been heeded by the corkwood industry and the waste is no longer such, rather standing as a cork product second only to the stopper, when the fact is considered that the grower or farmer receives about $58 per ton for raw corkwood and the waste sells from $22 to $32 per ton ”

“ When in this manner a continuous layer of cork arises, steadily increasing from the inside, it is termed “periderm.” As the epidermis is at first replaced by the periderm, so in turn is this replaced by cork (the dead tissue) . The development and configuration of the cork cells may change periodically during the formation of periderm. Alternate layers of narrow, thick-walled and broad, thin-walled cork cells are formed; the periderm then appearing stratified, like wood, showing annual rings as in the periderm of the Quercus Suber, Betula Alba, etc.” ”

“ Thus arises, usually parallel to the surface of the organ, a layer of cells capable of division, which continues to form new cork cells, the cork cambium or layer of phellogen. In general this is the innermost layer of the whole cork tissue, so that the production of cork advances outwardly and new layers of cork are constantly formed out of the phellogen on the inner surface of those already in existence. ”

“ Solid substances, with the exception of cork, offer [28] equally obstinate resistance to change of bulk; even India rubber, which most people would suppose capable of very considerable change of volume, we find it really very rigid. Metals, when subjected to pressure which exceed their elastic limits so that they are permanently deformed, as in forging or wire drawing, remain practically unchanged in volume per unit of weight. Not so with cork, its elasticity has not only a very considerable range, but it is very persistent. ”

“ As for life-saving buoys, properly so called, they consist of several cork planks which are given an annular form, and are provided with free ropes that are knotted here and there so that they may be easily grasped. From the stern of every vessel a buoy of this kind is suspended by a rope that may be at once cut when the cry of “A man overboard!” is heard. These buoys are usually covered with canvas coated with a paint that serves to preserve it. It is also possible to save a person who has fallen into the water at a certain distance from a wharf by means of floats. ”

“ In the French departments of the Landes and Gironde the Quercus Occidentalis forms extensive woods, as also in Spain, Algeria and in some parts of Italy, while the Quercus Suber is a native of the Atlantic side of France and Portugal, where this [13] tree grows to the greatest perfection, and to which countries we are indebted for the major part of our supply. The cork tree bears a general resemblance to the broad-leaved kind of (Quercus Ilex, Holm) or evergreen oak, of which species some authors consider it only a variety; but when full grown it forms a much handsomer tree. ”

“ American zone was all that could be desired for the favorable rearing of cork trees; but strange to say this was not the case. Although the growth of the tree had been exceptionally strong, the quality of its salient product turned out to be of an inferior character. The cork generally improves with the age of the tree; in this instance, however, even after years of maturity the cork harvest did not improve to any great extent, and indeed is still of a second-rate quality. ”

“ Anderson was most deeply impressed with the elasticity of cork, and has the following to say upon his findings: “It would seem difficult to discover any new properties in a substance so familiar as cork, and yet it possesses qualities which distinguish it from all other solid or liquid bodies, namely, its power of altering its volume in a very marked degree in consequence of change of pressure. All liquids and solids are capable of cubical compression or extension, but to a very small extent ”

“ The cork tree has in no wise escaped from disease and infections; on the contrary it has its full allotted share which worries the growers more than the acquiring of a perfect texture, and unless great care is taken will greatly reduce the value of a crop. ”

“ The poor of Spain lay planks of cork by their bedside to tread on instead of carpets. Sometimes they line the inside of their houses, built with stone, with this bark, which renders them very warm and corrects the moisture of the air. Loudon relates that in the celebrated convent at Cintra, Portugal, several articles of furniture are made of this tree. Virgin cork, or the first bark of the tree, is now very much used for window flower boxes, grottoes, etc., while the subsequent grades are used for small architectural and geognostic models. ”

“ The cork stopper industry had its permanent origin in Spain, in the Province of Gerona, town of Llacostera, towards the latter part of 1750 and was contemporaneous with the inception of the glass bottle, although corkwood was used many years before as a stopper for amphora, etc., as noted in a previous chapter.
The trade flourished there until wars and schisms rent the country and drove the industry to the mountains. There it slumbered and struggled for many years until the peace was restored and the people assured that the dangers were passed. ”

“ In taking up the processes of manipulation we naturally start from the beginning, but the beginning in this case has a peculiar significance as relating to the whole, for it is apparent to utilize corkwood to the fullest extent its qualities must be studied and the best, used first, so that the beginning of the corkwood industry is peculiar in this fact, that it takes the best part and leaves but scrap, which must be studied carefully to realize the value lost in the first process ”

“ When succulent organs of the higher plants, no longer in the bud condition, are injured, the wound generally becomes closed up by cork tissue, i.e., new cells arise near the wounded surface by repeated division of those which are yet sound, and these forming a firm skin separate the inner tissue from the outer injured layers of cells. ”

“ At the age of about forty years the oak begins to yield its best bark, continuing productive as a rule for [19] almost a century. [19] The cork of the first barking is called Corcho-Bornio, Borniza or virgin, and is so coarse, rough, and dense in texture that it is of little commercial value. The second barking is called “pelas,” or secondary cork, and this and subsequent barkings constitute the cork of commerce. As the bark is removed it is gathered up in piles (rusque) and left for a few days to dry. ”

“ As in the first processes of corkwood manipulation the best is taken first; so, in the department of waste utilization, a process is now used whereby the best scrap is made into cork disks for the Crown seal as described, and serves its purpose well.
This scrap is taken and granulated in an iron rotary cutter mill, to a degree of fineness that will pass a 1⁄8′′ mesh, it is then screened and mixed with a secret binder that has a wonderful holding quality; it is then dried by steam and pressed into sheets by hydraulic presses, dried again, and then stamped out in the usual manner. ”

“ Cork is not only useful as an application to foot gear, but also renders great service in head gear, and, in the form of helmets, has preserved a large number of soldiers from death by sunstroke in tropical countries. ”

“ The corky part of the bark which is outside is composed of closed cells, exclusively, so built together that no connection of a tubular nature runs up and down the tree, although horizontal passages radiating toward the woody parts of the tree are [26] numerous. In the woody part of the tree, on the contrary, and in the inner bark, vertical passages or tubes exist, while a connection is kept up with the pith of the tree by means of medullary rays. In one species of tree, known as the cork-oak, this is strongly developed. ”

“ It is used also by fishermen as floats for their nets.
These various applications were known to the Greeks and Romans, as shown by the works of Theophrastus and Pliny. The latter says of the cork-oak: “Nothing is utilized but its bark, which is very thick, and which is renewed in measure as it is removed. This bark is often used for the buoys of anchors and ships and of fishermen’s nets, for the bungs of casks, and for women’s winter foot gear. The Greeks called the cork-oak the ‘bark tree’.... Cork bark is used as a covering for roofs.” ”

“ In these cases the cork tissue is formed even before the destruction of the epidermis, and when this splits under the action of the weather and falls off, the new envelope formed by the cork is already present. The cork tissue is the result of repeated bipartitions of the cells by partition walls, rarely in the epidermis cells themselves, more often in the subjacent tissue. The partition walls lie parallel [24] to the surface of the organ, divisions also taking place in a vertical direction, by which the number of the rows of cells is increased. ”

“ The thickness of the bark ranges from 1.27 centimeters to 6.85 centimeters, while the yield also varies greatly [18] from twenty to 75 kilograms [18] per tree, depending upon its size and age. After the first stripping the tree is left in the juvenescent state to regenerate, and great care must be taken in the stripping not to injure the inner skin or epidermis at any stage of the process, for the life of the tree depends upon its proper preservation, for if injured at any point, growth there ceases and the spot remains forever afterward scarred and uncovered. ”

“ Cork Stopper Making
After the sorting, the slabs are placed in steam boxes and subjected to a steam bath, which it is claimed softens the material and also prepares it for the scraper, who cleans and removes the dirt and callous or “raspa” accumulated in its mountain home. This scraping is done either by hand or machine, the handwork being done with a short handle, curved bladed knife called a “doladera,” raspador or raspeta: a workman being able to scrape from two to three metric quintals of cork in a day, or ten hours. ”

“ It will be readily seen that if disks are cut horizontally parallel, that is, the annual layers running at right angles to the axis of the disk, this grade of cork can be utilized to great advantage. The mode of cutting is by a horizontal revolving blade, which slices the cork to the desired thickness, usually a quarter of an inch, and then it follows the usual course of punching, etc. From these operations a great deal of waste accumulates, and this would be a great loss if methods were not devised for its utilization. ”

“ The manufacture of stoppers and of the various objects that we have just enumerated furnishes a considerable quantity of chips, which along with the waste derived from the collecting of the material, and with old, second-hand corks, constitutes the crude material destined to supply certain important industries, which, for the sake of completeness, must be mentioned. ”

“ If the soil is poor, the cork is thin but of fine quality and very appropriate to make the best stoppers. If, on the contrary, it is rich, the cork is thick but spongy. Consequently it is requisite to treat the cork tree in such a manner that whilst the cork grows thick it will at the same time be fine in texture. ”

“ In further defining the various substances which go to make up the body of corkwood the one that is most impressive is that substance that is peculiar to cork itself, the others being readily known, but suberic acid is the one of interest, and this is described by Fownes as a product of the oxidation of cork by nitric acid ”

“ We have first the cork powder industry, which manufactures powders of various degrees of fineness. The coarsest powder is used for packing fragile objects, on account of its elasticity, coupled with its lightness, which permits of a great saving in freight charges. ”