All types of linoleum pass through these mixing stages—the nature of the finished product being determined by the subsequent treatment of the granulated material.
Linoleum can be divided into two broad classes: (a) Plains, and (b) Inlaids. These can again be further sub-divided, from the manufacturing point of view, into—(I) Plains, Printed, Jaspes, Granites and Moires. (2) Inlaids—Moulded, Straight-line, Gran ites, Parquetries and Marbles.
Plain and Printed Linoleums.—The granulated material is calendered on to the canvas backing by heavy steam-heated rolls. The same type of material is used for plain and printed goods, but the latter are usually thinner, and have the pattern printed on in oil colours afterwards. Granites, Jaspes and Moires are, with modifications, made in the same way, the variously coloured scratched materials being blended before calendering. Cork Carpet and Corticine too are made similarly, but have a base of polymerized (Taylor) oil incorporated with cork dust and pig ments.
Inlaid Linoleum.—When produced by the moulding process, the granulated material of different colours is sifted through sten cils on to canvas lying on a table. A separate stencil, having perforations corresponding to the desired position in the pattern, is used for each colour, the scratched material being thrown on and the perforations filled. The completed pattern is afterwards put through a flat hydraulic "making press," to consolidate it, and the face is perfected by passing through a "finishing press." This method gives very fine carpet and floral effects.
Straight-line Inlaids.—For these two processes are used. (a) Hand-made : the stencils in the moulding process are in this case replaced by pieces of previously sheeted material, cut to the desired shape, and laid on to form the pattern required. The rest of the operations are as in the moulding process. Parquetries, Marbles and Tile patterns are made in this way. (b) Machine made : in this process the scratched material is rolled into a con tinuous sheet, and led, together with the backing, under a revolv ing "cutting cylinder." In the periphery of the cylinder steel knives are embedded, forming a complete pattern. Between the knives plungers operate selectively from the inside and place on the canvas the tesserae of the particular part of the pattern required. The pieces not required are carried round between the knives and are ejected.
A series (up to six) of such rolls and cylinders are used to place the different coloured pieces into position, where they are maintained by pins projecting through the backing until the "pressing cylinder" is reached. This machine consolidates the
pattern and presses it on to the canvas.
Linoleum obtained by any of the above processes is still in a soft (green) condition, and requires to be hardened by seasoning. This is carried out in drying rooms; the stoves are heated from 90 to 170° F for 2-60 days according to the type of linoleum. Linoleums are usually made 2, 3 and 4 yards wide (metres in European countries) and the thickness may vary from 1.9mm. to 8mm. for plains, and 1.4mm. for inlaids.
It is computed that the world's output of linoleum is in the region of 200,000,000 sq. yds. per annum.
Important developments have taken place in the last few years, in an endeavour to improve the quality of linoleum, by using materials other than linseed oil as a base. • Nitro-cellulose.—In common with all industries using drying oils, great progress has been made in attempting to replace the linseed oil in linoleum with a nitro-cellulose base. In Germany, large quantities of linoleum are being produced containing nitro cellulose and plasticizers as the binding material. The most recent of these products contains also a proportion of linseed oil "cement." In America, practically all types of linoleum produced are now coated on the surface with a nitro-cellulose composition, which has the advantage of giving a non-marking, glossy finish, highly resistant to soap and soda.
Felt Base.—Felt, impregnated with bituminous composition, is being used as a substitute for linoleum material. It is coated and then printed with a pattern. Such printed felts are being produced in America and Europe on a large scale and rival the production of printed linoleum.
BIBLIOGRAPHY.-The literature on linoleum is relatively small, but the following may be consulted:—Society of Arts Journal (1862) Wal ton; The Society of Chemical Industry Journal, Reid (1896) 75; Ingle (1904) 1197; Jones (1919) 26T; Martin, Industrial Organic Chemis try (1913) ; Industrial & Engineering Chemistry Journal, de Waele (1917) 9.6.18; Livache & McIntosh, Manufacture of Varnishes, Vol. I., (1919) 232; Alder Wright, Oils, Fats and Waxes (1921) ; Lewkowitsch & Warburton, Chemical Technology of Oils, Fat & Waxes, Vol. III. (1923) ; Fischer, Geschichte, Eigenschaften and Fabrikation des Linole ums (1924) ; The Industrial Chemist (Sept. 1925) ; The American Exporter (Oct. 1925) ; Die Tapete (Aug., Oct. 1925) ; Walton, The Infancy & Development of Linoleum Floorcloth (1925) ; Morrell & Wood, The Chemistry of Drying Oils, 1925; A.-D. Luttringer (1928), La Linoxyne et le Linoleum.