LINOLEUM is a kind of floor-cloth, invented and introduced by Mr F. Walton, who in 1860 obtained a patent for its manufacture. It consists of a preparation of linseed oil and ground cork intimately mixed and spread in a uniform layer over a sheet of rough jute canvas. Under the name of kamptulicon, a material similar in appearance and properties, but in which prepared india-rubber took the place of oxidized linseed oil, was in use to a limited extent previous to the introduction of linoleum ; the latter material, however, was found to possess several advantages; among others it had the merit of comparative cheapness as against kamptulicon, which it entirely supplanted. Linoleum also became a formidable competitor with the old form of oil floor-cloth, and on the expiry of Mr Walton's patent the manufacture of the new material was very generally taken up in Kirkcaldy, the principal seat of the floor-cloth trade. In the hands of Messrs Michael Nairn & Co., who were the first to introduce the floor-cloth industry into Scotland, the machinery used for making linoleum has been improved in important respects, and the ingenuity and resource of Mr Walton, the original patentee, have discovered several new adaptations and modifications of his original invention.
The making of linoleum involves three distinct preliminary operations(1) the oxidation of the linseed oil, (2) the grinding of the cork, and (3) the weaving of the jute canvas backing. Of these operations the oxidation of the oil is the most peculiar and distinctive. The linseed oil is first boiled with litharge in the way practised for pre-paring ordinary boiled oil (see LINSEED), and it is next oxidized by exposure, in exceedingly thin films, to the influence of air. To secure the exposure of sufficient surfaces of oil to the atmosphere, a large lofty apartment is hung with sheets or continuous webs of calico cloth, which are allowed to depend from near the roof into troughs or tanks on the floor. These webs of calico are kept suf-ficiently far apart to allow free circulation of air between them. They are daily drenched with boiled oil by allowing it to trickle down from the top over their entire surface, the distribution being effected by a special arrangement of movable tanks and tubs. It will be seen that an enormous surface of oil can thus be exposed within a comparatively limited space. The influence of oxygen on the oil films is facilitated by the blowing of heated air into the chamber so as to keep up a continual circulation ; and the activity of the process is unpleasantly manifested by the extremely acrid odour which is evolved by the oil. Day by day the thickness of the coating of oxidized oil increases, and when a deposit of about half an inch has been accumulated, the drenching is stopped. The product, now ready for being withdrawn, forms firm translucent sheets of a caoutchouc-like substance having a straw yellow colour, possessed of a certain amount of elasticity, and communicating no oily stain to paper. These sheets are now torn into small pieces and reduced to a uniform plastic mass by means of powerful crushing rollers, after which the material is placed in a close boiler with the addition of certain proportions of kawrie gum, rosin, and ochre, umber, or other pigment, according to the ground-colour desired. The boiler is heated by steam, and the entire mass, being thoroughly incorporated by means of stirrers, is run into a shallow trough, from which, after cooling and solidifying, it is taken in large slabs. These are piled up awaiting future use, and when required for manufacturing purposes they are cut into blocks about the size of au ordinary brick.
Ground cork, which is the second essential constituent of linoleum, may be made from cork cuttings and scraps; but, the supply of such material being unequal to the demand, bale cork, of secondary quality as imported, is very largely used. It is first broken to pieces about the size of a nut; the fragments are fed into the hopper of a mill: and the cork passes thence between a pair of ordinary millstones in which it is reduced to a meal-like condition, in exactly the same way as wheat is ground to flour. The product is sifted, and the insufficiently ground portions are returned to be passed again through the mill. In the grinding of the cork great care is necessary to prevent iron, stone, or other hard foreign material from getting into the mill, as sucn substances, causing sparks between the stones, readily give rise to explosions in air so laden with fine dust as that of the mill necessarily is.
In the making of the jute backing the only notable feature is the great width of the loom, in which webs 12 feet broad are woven by Messrs Nairn. The maximum width of that produced by other makers, however, has hitherto been 6 feet.
The actual preparation of linoleum floor-cloth in the factory of Messrs Nairn is conducted in a continuous series of operations by machinery which has been patented by that firm. The bricks of oxidised oil and the requisite proportion of cork are thrown into a hopper, where they are thoroughly mixed in a kind of pug mill, whence the mixture is shot forward in a tube, at the open end of which it is sliced off in thin crumbling masses by a revolving knife. Spread out in thin sheets, it passes from this between a series of steam-heated rollers, from the last of which it is scratched off by a circular drum covered with sharp steel points, and falls in a fine shower into a feeding box the whole width of the linoleum to be made. From this feeding box the mixture is uniformly delivered on the surface of the canvas, which here meets it, and passing immediately between powerful smooth rollers, the semi-plastic mixture is firmly squeezed on the surface of, and rendered adherent to, the rough open canvas which forms its back. The distance between the upper and lower compressing roller determines the thickness of the linoleum, three standard thicknesses being recognized, viz., and ^2 parts of an inch, Linoleum of the thickness of |-of an inch is also made for public libraries and reading-rooms on account of its perfect noiselessness. It only remains to coat or waterproof the raw canvas back with oil paint, and the floor-cloth is finished as plain linoleum. The printing of patterns in various colours on its surface is done as described under FLOOR-CLOTH, vol. ix. p. 329. Corticine is a form of linoleum, in which the oil is oxidized by chemical agents.
Recently a method ot ornamenting linoleum with patterns in the form of tiles or tessarse, the colour of each tile gclng right through to the canvas or sufficiently deep for constant wear, has been devised and patented by Mr C. F. Leake. The patentee prefers to use canvas first covered with a thin linoleum coating. This he brings on a table on which are a series of moulds corresponding with the coloured tile pattern required. Into each mould is put the required quantity of properly-coloured granulated linoleum material,
which is compressed into solid tiles by the descent of plungers. The part covered by the pattern is carried forward and powerfully squeezed between hydraulic rams, the tiles being thus made smooth, homogeneous, and firmly adherent, while in the meantime tin-moulds are being filled and a new set of tiles prepared in the first stage of the operation. Mr Walton, the original patentee of linoleum, has adapted a preparation of oxidized oil and cork or other
thickening material embossed with patterns for wall decorations under the name of "Lincrusta Walton." (J. PA.)
The above article was written by James Paton.