Part 3

But to the data assembled may be added much in commentation, for the material becomes more interesting the more it is studied, and most naturally excites comparison with other materials and substitutes, as well as calling forth a discussion as to the dangers involved by its presence in the places where, by skill of hand and machinery, it is transformed into the many commercial forms, noted in this article. We comment upon its growth, which is truly wonderful and all-absorbing in its many interesting phases; it takes us to the romance of the East and the enchantment of the Moorish occupation; through which these forests of cork-producing trees passed and yet remain to furnish the present generation. We comment upon its lightness and buoyancy, due to the presence of air and excess of hydrogen, known to be lighter than air; and the small percentage of other matter which, being of less importance, make its other quality so renowned as to make it the most wonderful growth of its kind. Its imperviousness to water and other liquids have given us moments of reflection, upon this phenomenon, but now known to be because of the cellulose composing the cell walls and which, when the substance is under compression, practically is all that remains, except for the small quantity of resin, etc., to resist the passage of liquids or gases. But heretofore when these commentations have reached the burning point, its physical nature was entirely eliminated from the conjecturing and the important part neglected, that as the cork contained fifty-three per cent of air, heat of 450 degrees expands to the point of explosion, the contents of those cells nearest the surface, which giving up their oxygen feed the flames and in their passage help to disintegrate the cell walls and make them more easily ignited. Thus causing a rapid burning, flash fire which, in its fury, Pluto could not rival, only racing over the surface of the cork, burning but slightly, yet helped by other conditions, resulting in a fire destructive and fierce. This rapid burning leaves the outer surface of the cork charred and flaky and causes a discoloration beneath it attributed to the dissolving of the resins, etc. Of course where there is a large quantity of corkwood the extent of the burning must necessarily be greater and the depth of the char increased. But it appears that the first flash burning produces a sort of protection coat of carbon around the remaining unburned portions which a subsequent flame penetrates with difficulty.[28]

[28] In the making of insulation material, the carbonization of the cork is accomplished without destruction of fibre and stands a high flame test.

A simple experiment to show this depth of burning, and one that is easy to do, is the flash and flame test which was found of interest.

Two pieces of cork were taken, having the following measurements—8/16″ × 7/16″ × 11/16″—and the first piece held so that the flame of a gas jet would cause a flash over its surface; then the second piece is taken and held within the flame for a minute.

It will be found that the corkwood has expanded and the dimensions increased to the following:

Flash Flame 8/16″ × 13/16″ × 11/16″ 10/16″ × 14/16″ × 11/16″

showing the effects of the heat upon the tissue and contents of the cells.

Now in scraping these samples clean of all char the dimensions will return to the following:

Flash Flame 6/16″ × 11/16″ × 11/16″ 8/16″ × 10/16″ × 11/16″

clearly setting forth the fact that the char is comparatively light in both cases, ranging from 1/8″ to 1/4″.

To this cause is ascribed the burnability of cork having by careful observation and experiment, extending over a period of two years, studied the results of numerous fires in premises where cork was being worked and also conducted heat applications on various grades of cork[29] resulting in the foregoing findings.[30] Thus it is found that cork contains sufficient air to supply any fire in it and precludes the necessity of free access to any outside supply which makes it a material worthy to be watched. To its many qualities of great service to man, giving him a material which from the ages past, till now, has proven of such value, must be added this one, no less important than others, which heretofore have been its commendable features.

[29] Using ordinary glass (armoured) thermometer for ascertaining degrees.

[30] One thousand degrees Fahrenheit, causing no greater combustion than the lower degree, other than the increased burning of remaining substance after the flash, due to the higher temperature.

Rather than attend the “cork” through the many passages of commerce and manufacture, it is deemed propitious to deviate a little from a natural course, i.e., from the growing to manufacture and rather advance to a knowledge of the many uses to which this material is put and its application to the innumerable arts, and then take up the manufacture.

USES AND APPLICATION

Mr. H. G. Glasspoole,[31] writing regarding the uses of cork by the ancients, states: “The cork-tree, and the application of its bark to useful purposes, was well known to the Egyptians, Greeks and Romans. The former used this material in the construction of the coffins for their dead. Theophrastus, the Greek philosopher, who wrote on botany four centuries B.C., mentions this tree among the oaks, under the name of ‘Phellus’ in Book Two of his ‘Historia Plantarum,’ and stated that it was a native of the Pyrenees, having a thick fleshy bark which must be stripped off every three years to prevent it from perishing. He adds that it was so light as never to sink in water, and on that account might be used for many purposes.” It is the opinion of the writer that the attention of the ancients was undoubtedly called to this particular bark by its buoyancy, and as their fisheries were extensive its usefulness became readily apparent to float nets, etc., or to use even in the construction of their boats, and its sponginess and water-repellent properties not escaping their notice, it became a most likely material for stoppers of casks or amphorae as noted by Horace in Ode iii, 8: “Corticem adstrictum pice dimovebit amphorae.” Pliny, in his “Natural History,” XVI, 18, describes the tree under the name of Suber and relates everything said by Theophrastus of Phellus. From his account we learn that the Roman fishermen used it as floats to their nets and fishing tackle, and as buoys to their anchors. The use of these buoys in saving life appears to have been well known to the ancients, for Lucian, Epist. i, 17, mentions that when two men, one of whom had fallen into the sea, and another who jumped after to afford him assistance, both were saved by means of an anchor buoy. The use of this substance in assisting swimmers was not unknown to the Romans, for Plutarch in his Life of Camillus, who flourished in Rome 400 B.C., gives an account of its use by a messenger, sent to the Capitol, then besieged by the Gauls: “Pontius Cominius having dressed himself in mean attire under which he concealed some pieces of cork. He could not pass the river by the bridge, therefore took off his clothes, which he fastened upon his head, and having laid himself upon the pieces of cork swam over and reached the city.” The use of cork as stoppers was entirely unknown to the Romans, but instances of its being employed may be seen in Cato’s “De Re Rustica,” Cap. 120, but this did not happen frequently or more would be said of it.

[31] _Scientific American Supplement._

The convivial customs of those days had no connection with the bottle, glass bottles being of a much later invention. Instead of having champagne or hock to be liberated from the bottle by the corkscrew at their feasts, the guests filled their drinking cups of gold, silver, crystal or beechwood from a two-handled amphora, a kind of earthenware pitcher, in which their choice wines used to be kept. The mouths of these vessels were stopped with wood and covered with a mastic, composed of pitch, chalk and oil to prevent air spoiling the wine or evaporation taking place. Columella, who wrote one of the earliest works on agriculture, gives directions for preparing this cement.

The employment of cork for stoppers of bottles appears to have come into use about the seventeenth century, when glass bottles, of which no mention is made before the fifteenth century, began to be generally introduced. Before that period apothecaries used stoppers of wax, which were not only much more expensive but far more troublesome. In 1553, when C. Stephanus wrote his “Praedium Rusticum,” cork stoppers appear to have been very little known in France, for he states that this material was used principally for soles in that country. It is not known when cork and corks began to be generally used, but in that very amusing and instructive diary of Mr. Samuel Pepys the following entry is found: “14 July 1666” After having written to the Duke of York for money for the fleet, I went down Thames Street and there agreed for four or five tons of cork to be sent to the fleet, being a new device to make barricados with instead of junts (old cable),” but he does not inform us how the material answered.[32]

[32] I have subsequently learned that this proved a failure.

In Evelyn’s time (1664) cork was much used by old persons for linings to the soles of their shoes, whence the German name for it, “Pantoffelholtz” or slipper wood. The Venetian dames, Evelyn says, used it for their choppings or high-heeled shoes to make them appear taller than nature intended they should be. 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. Cork was formerly employed in medicine even as far back as the time of Pliny, as he tells us that the bark of the cork tree, pulverized and taken in warm water, arrests hemorrhage at the mouth and nostrils, and the ashes of it taken in warm wine are highly extolled as a cure for spitting blood (see Pliny, “Nat. Hist.” b. 124). In modern time powdered cork has been applied as a styptic and hung about the necks of nurses. It was thought to possess the power of stopping the secretion of milk. Burnt cork mixed with sugar of lead has been used as an application to piles. See Pereira’s “Materia Medica.”

Ground cork and India rubber formed the basis of Kamptulicon, the soft unresounding material which covered the floor of the reading rooms of the British Museum.” In further describing the many uses to which cork is applied, reference is made to the résumé of Mr. Good in “La Nature,” which is incorporated with a few slight changes.

“The various applications of cork that we are now going to pass in review are worthy of description, as each of such applications has its _raison d’être_ in one or more of the physical or chemical properties of cork bark. The manufacture of stoppers utilizes, in the first place, the impermeability of the bark, and, in the second, the latter’s elasticity and imputrescibility, the remarkable lightness playing no rôle therein.

Before entering upon a study of the industrial applications of cork, in grouping them according to the various qualities of this product, we must return to the “male” cork, derived from the first barking of the tree. It has been said, because of its slight elasticity and numerous fissures, this product has but little commercial value, and shall have mentioned its principal application when we have stated that it is used in the decoration of parks and gardens. An endeavor has been made, but without success, to manufacture from it, mills for decorticating rice.

Certain parts of it can be converted into small stoppers. In the country where it is produced, it is used for making water conduits, beehives and shelves on which to preserve objects from dampness. Mixed with a mortar of clay, the Kabyles use it for the walls of their dwellings, and also, in lieu of tiles, as a roofing material for their primitive habitations. 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.” (“Hist. Nat.,” xvi, 18.) As for the chips, they can be used as an isolating material to prevent freezing. Reduced to fragments, they furnish an excellent material for covering circus rings.

Let us return to “female” cork, which is much better adapted for being worked, and the grain of which is much more homogeneous. In this form cork bark constitutes a very bad conductor of heat and sound, and renders valuable services in the industries as a material for preventing the cooling of steam pipes and generators, and preventing the melting of ice in ice houses, or the heating of apparatus for producing cold.

It is the basis of a certain number of cements, and coatings for preventing the escape of heat, which are applied to pipes, steam domes, hot water reservoirs, etc., and upon the composition of which we shall not dwell here. As for jacketing with cork alone; the first method consists in placing narrow strips of cork, whose edges touch each other, along steam pipes and cylinders, and fastening them by means of wire. A pipe thus jacketed is tangent internally to all these strips, and a section of the whole shows a circle inscribed in a polygon. In the second system thin strips of cork, fastened to canvas with India rubber cement, are wound around the pipe spirally. Finally, a third method of jacketing consists in the use of two half cylinders that exactly fit the exterior of the steam pipe. These cylinders, which can be made of any desired length, are made of powdered cork and starch, and are covered with a spirally wound strip of calico, which may be coated with tar or any suitable kind of paint. Each of these systems permits of obtaining a great saving in fuel.

As cork is likewise a very bad conductor of sound, it is successfully used on the doors of consulting rooms, and for making floors for hospitals, etc. Finally, in the manufacture of certain stringed instruments, it is used to prevent a loss of sound.

The slight density of cork, as compared with water, and its impermeability to liquids, make it an excellent float, capable not only of remaining on the surface, but also of supporting quite heavy bodies thereon. We shall be content to mention the annular cork float used in night lamps, the square block in which bath thermometers are fixed, and the fisherman’s dobber.

It is cork, too, that is used by preference in the manufacture of swimming and life-saving apparatus, to which inventors have devoted much thought. Very many vessels are provided with cork mattresses, which, in cases of shipwreck, render the greatest services. For example, the ship _Constant_, which sailed from Anvers for Brazil in 1845, was wrecked on the night of October 12th, at twelve miles from St. Thanes, but, thanks to the cork life preservers and mattresses that she had on board, not one of the crew was lost. 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. This device consists of a piece of rattan provided with points around which molten lead has been poured, and the whole is then surrounded with cork in chips, and covered externally with canvas and a network to protect the affair against wear.

Fenders are canvas bags that are filled with cork and are placed along the sides of ships or along docks in order to deaden the shock in case of a collision. Such are the principal uses rendered to navigation by cork.

It has already been seen, by the extract from Pliny, that Roman ladies preserved their feet from cold by means of cork soles. Such a use of cork is still in vogue. In addition to these soles, which are flat, there are others that have nothing to do with hygiene, and are merely connected with fashion. Such are the Louis Quatorze talonettes, designed to increase the stature without exaggerating the heel of the shoe. Female dancers wear linings of this kind in their shoes, which, as well known, have flat soles. A thin sheet of cork enclosed in the sole of the shoe would, we think, prove very useful to troops on a march during bad weather.

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. We find it again, in the form of very thin sheets, in the interior of beaver hats, where it is used as a protection against heat. It is also used in these same hats as a sweat band, in lieu of leather. In ladies’ toilets, the cork serves to make the carcasses of the birds that decorate their head gear. Manufacturers of dress trimmings use cork molds, which they cover with silk or cotton, for ornamenting cloaks, etc. The lightness of cork can alone explain the great size of these balls, olives, etc., some of which are larger than a hen’s egg.

A few years ago, a Paris house sold cork cravats, and we have recently seen, exposed in a show case, some children’s costumes, in which the sailor’s collar was of thin sheet cork decorated with colored designs. Although cork gowns have not yet appeared, we have waterproofs composed of thin sheet cork cemented between two pieces of silk. These cloaks have the advantage over those made of rubber of not allowing air to pass through them.

There is also a curious application of cork in the manufacture of a fabric that renders those who are clothed with it insubmergible.

We can mention but few of the many applications of cork, new ones of which are being discovered every day, so shall confine ourselves to recalling the services rendered by this valuable product in surgical prosthesis and for the use of naturalists, etc. In domestic life, it is used for bath steps, and for making rolling pins for crushing almonds without absorbing the oils as wood would do. Thin sheets of it are used for making fancy labels for wines. The ease with which it may be cut, turned and worked causes it to be employed in the manufacture of small objects, such as rural landscapes and the reproductions of monuments, some of which are genuine works of art. We may likewise mention, among objects made of cork, cases of various forms for sending bottles by mail, spools for allowing of the cheap carriage of silk, the old-fashioned inkstand, the thick penholder for preventing writer’s cramp, the cigar holder and many fancy objects that would take too long to enumerate. There is perhaps no calling that does not have to make more or less use of cork. Polishers of gold have used it from time immemorial, in the form of narrow strips, for rubbing their work with rouge. The wheels with which crystals are polished are faced with it, and watchmaker’s lens mounted in cork, the lightness of which prevents the muscles of the face from tiring.

In the industries, driving pulleys are now beginning to be provided with cork in order to secure an adhesion of the belting. In carpenter shops these bands of cork are now advantageously replacing rubber ones for covering the pulleys over which the band saw runs. The stoppers of nursing bottles are now being replaced by hygienic ones of cork, which, being very cheap, can be changed as soon as the presence of ferments is suspected. Cork is likewise employed in the manufacture of children’s toys; it serves, for example, for fixing the wig on dolls’ heads. Is it necessary to recall the cork of pop-guns and pistols, and the cork battledores and shuttlecocks used for playing with indoors? These few data will serve to show that but few products are capable of so many diverse applications as cork is; and the question may be asked whether it would be possible to substitute anything else for it, in case the supply should become exhausted.

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.

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.

The finest powder forms, “liegine” or “suberine,” whose balsamic properties are well known to hygienists, and which may be used as a substitute for lycopodium, starch and fecula as an application to the skin of babes. Under the name of “zifa powder,” an insect powder has been made composed of cork and phenol. Fire lighters have likewise been made from cork powder; but this and the last named application have not amounted to much.

We cannot enter into much detail in regard to the manufacture of linoleum, notwithstanding the interest that it presents. The manufacture began in Scotland, and is tending to settle in our own country. Linoleum is made by intimately mixing cork powder with oxidized linseed oil. The paste thus prepared is spread over canvas if the intention is to manufacture carpets, but over paper if it is desired to make hangings. The color of linoleum, which is the same as that of cork, only a shade darker, can be enlivened by colored designs. When applied to damp walls, linoleum is capable of receiving oil paintings of a more stable nature than those executed upon wood, which warps, or upon other building materials, which crack, such as plaster, for example. It can also be used for decorated ceilings for public halls, cafes, etc.; and when such ceilings become black through smoke and dust, they can be washed.

As a carpet, linoleum renders flooring perfectly insonorous. It converts damp and unhealthy apartments into healthy and warm places of habitation. Used in kitchens and offices, it has the advantage of not being spotted by fatty matters. It has been generally adopted in our naval and merchant ships, where the use of it has given a great setback to the oil cloth industry.

A new decorative product, “lino-burgau,” obtained by embossing linoleum, possesses the iridescent reflections of nacre, due to the application of colored varnish along with a bronzing of certain parts. Notwithstanding its expensive nature, we believe that there is a great future in store for it.