Floorcloth. There are several kinds of floorcloth. Formerly the name was confined to painted canvas, which is now called oilcloth; but the more recently introduced linoleum and other fabrics in which ground cork bulks largely are now extensively used for covering floors.
Oilcloth.—The basis of oilcloth is a coarse canvas generally made of jute, but it is stronger when made of flax tow. It is woven into pieces often as long as 150 yards and as wide as 8 yards. The first step is to fix a piece of this, say 75 feet in length by 24 feet in width, upon an upright frame provided with screws by means of which the canvas can be uniformly stretched. Stages or platforms are placed at convenient heights to enable the workmen to cover the canvas. Before paint is applied the canvas receives a coating of size, the chief object of which is to prevent injury to the cloth by acid products arising from the oxidation of the linseed-oil with which the paint is made up. When the size is thoroughly dry and pumiced, a layer or coating of paint is put on with steel trowels like those used by plasterers. Yellow ochre is much used for this thick coating, which if unaided by artificial heat sometimes takes fourteen days to dry. A second coat is applied in the same manner to finish the back, but the face receives five or six trowel coats, the surface being once or twice pumiced between the coats. The wearing surface receives a coat of paint with a brush if some other colour than that of the last trowel coat is wanted for the ground shade. In the case of cheap oilcloths, the coats of paint, instead of being applied by trowels, are put on by a roller machine. A man keeps pouring the prepared paint out of a bucket on the moving canvas, and a long blunt knife-blade, almost touching its surface, regulates the thickness of the coat of paint. When made by this method, the oilcloth receives nine coats.
In printing, wood blocks are chiefly used, a separate one being required for each colour of the pattern. These are about 18 inches square, and the face is commonly made of pear-wood, with a pattern cut out by steel tools. There is an ingenious way of producing patterns on wood blocks by heated iron punches. Sometimes the raised portions of these printing-blocks consist of type-metal or brass. Figs. A, B, C, D (Vol. II. p. 645) of the article CALICO-PRINTING will give an idea of how the impressions from several blocks complete a pattern. Beside the printers there is a table upon which are placed the colour-pads. Another table, padded with felt or flannel, supports the floorcloth, each pattern block, charged with colour, being applied by means of a small screw-press. A machine is in use for printing floorcloth which to a certain extent imitates hand-printing. The blocks which form the pattern are depressed by cams carried on shafts. Roller machines are not applicable to this kind of printing, because the paint would 'run' on a revolving surface. The durability of oilcloth depends very much on the length of time given for the paint to harden, and also upon its quality.
Linoleum.—The floorcloth called by this name snits the purpose for which it is made admirably, being lasting, comfortable, and noiseless when trod upon. Its wearing face consists chiefly of pulverised cork and oxidised linseed-oil, with smaller quantities of common and kauri resin, all well mixed together, and made to adhere to canvas backed with size and pigment.
The chief operations in the manufacture of linoleum are based upon processes patented by F. Walton in 1860 (specification No. 209) and in 1863 (specifications No. 1037 and 3210).
Of these the more important are the preparation of the cork, the oxidising of the oil, the formation of the mixture of all the ingredients for the coating, and the application of this to the surface of the canvas. Pulverised cork, of which linoleum most largely consists, is obtained from waste cork-cuttings. These are exposed to the action of a series of toothed steel discs revolving on a shaft and working against steel plates, the ends of which have also teeth like those of a saw. By this machine the cork is reduced to the size of peas. It is afterwards ground with millstones.
The oxidised linseed-oil is produced by diffusing or 'flooding' the boiled oil in thin films upon the surface of long pieces of calico or scrim, placed in an upright position. This is repeated daily till the successive films of oil reach half an inch in thickness. It takes six or eight weeks to effect this, and the scrim with its many films is then called a skin. Owing to the injurious action upon vegetable fibre of the vapours given off during the oxidation of the oil the scrim becomes completely rotten. Even mineral substances are attacked by these vapours. The gain in weight shows that a large quantity of oxygen is absorbed by the boiled oil, and that a good supply of air in the oxidising buildings is therefore necessary. After being cut into small pieces the skins are ground by means of grinding-rollers. Care must be taken not to heap up the pulverised material, as in bulk it is very liable to char or ignite by the rapid oxidation of such particles as have not undergone this change previous to grinding.
A mixture is now made consisting of from 4 to 8 cwt. of the oxidised oil to 1 cwt. common resin and 1 cwt. kauri resin, the mixing operation being conducted in a pan with an outer jacket or casing containing steam. The pan has an air-tight lid, and at a valve at the bottom and inside there are stirrers. Resin is first put in and melted, the oil and kauri being separately added. As soon as the mixture is warmed the steam is shut off, the oxidation of the materials keeping up a sufficient heat till the charge becomes homogeneous. The valve at the bottom of the pan is then opened, and the mixture, now called cement, passes down between grinding-rollers. The cement is next cooled, but before mixing it with ground cork it is again heated to at least 120° F. The proportions of these two ingredients are about equal, but sometimes the cork is rather in excess of the cement. The colouring materials (ochre and oxide of iron) are either added with the cork or previously to the cement.
There is still another mixing-machine—the most important of all. Here the material is fed by a hopper into a cylinder in which both fixed and revolving knives are placed. It has a steam jacket. When the linoleum mixture leaves this machine, the cork and cement are so thoroughly mixed that they are scarcely distinguishable by the naked eye. The next operation is to pass the mixed material between two rollers, one of which is steam heated, and the other kept cool by a current of cold water. Here it is formed into a sheet, which is then broken up by a similar arrangement of rollers, one of them being studded with points for the purpose of breaking up the linoleum material into small pellets. Finally the mixture is spread over and pressed into the canvas by a pair of rollers of chilled cast-iron heated by steam to a high temperature. The canvas afterwards receives a backing of size and pigment, and then the linoleum is finished if it is to be left plain. When a pattern is required it is printed in the same way as upon oilcloth. A mosaic linoleum, in which the pattern is made of cut pieces of coloured material fixed on a thin backing, was patented in 1882 by F. Walton. By the improved method perfected by the inventor, the pattern extends quite through the material, and shows exactly the same on both sides. The work is done automatically by a machine which mixes and manipulates the ingredients, rolls the material into sheets of various colours, cuts these sheets into pieces of the desired shapes, arranges them into patterns with unfailing accuracy, and finally rolls and solidifies the whole into a compact sheet with the required pattern.
Kamptulicon, which is made of ground cork and india-rubber, was introduced earlier than linoleum, but its manufacture has almost ceased.
Cork Carpet, a floorcloth the manufacture of which has been quite recently begun. It is made of cork bound with oxidised linseed-oil, but differs from linoleum in having the particles of cork larger and purer in colour, as no pigment is mixed with it. It has a canvas backing, and is the warmest kind of floorcloth.