FELT, a fabric produced by the "matting" or "felting" to gether of fibrous materials such as wools, hairs, furs, etc. Most textile fibres (see FIBRES) possess the quality of matting to some extent, but wools, furs and some hairs are the only fibres which can be felted satisfactorily. It is probable that the quality of felt ing must be attributed to the scale structure and waviness of the wools, furs and hairs referred to and to the "fibre-stuff" of which they are composed. When it is desired to incorporate non-felting fibres in felt cloths, wool or fur must be employed to "carry" them.
There are two distinct classes of felts, viz., woven or "thread structure" felts, and "fibre" or true felts. In the manufacture of thread-structure felts, wools possessing the quality of felting in a high degree are naturally selected; carefully scoured so that the felting quality is not seriously damaged; spun into woollen or worsted yarns possessing the necessary fibre arrangement and twist ; woven into cloth of such a character that subsequently sat isfactory shrinking and felting may be done; and finally scoured, milled in the stocks or machine or both ; dyed and finished on the lines of an ordinary woven fabric. The lighter styles of woven felts may be composed of a single cloth only, but for the heavier styles two or more cloths are woven, one on top of the other, at one and the same time, arrangements being made to stitch the cloths together during the weaving operation. Some special felts are made by cementing or glueing together several layers of fabrics.
Fibre felts are exceedingly interesting from the historical point of view. It is now generally admitted that the art of weaving pre ceded that of spinning, and it must further be conceded that the art of felting preceded that of weaving, so that the felt fabric is probably one of the oldest of the various styles of recognized fab rics. The inhabitants of the middle and northern regions of Asia seem to have employed felt from time immemorial, as clothing and also as a covering for their habitations. Most of the classical writers refer to it and some of them actually describe its manufac ture. Felt was also largely employed by the ancients for their hats, outer garments, and sometimes as a species of armour.
The wools used for fibre felts are generally short to medium in lengths, and must have good felting quality and be carefully selected and blended according to the characteristics required in the felt. The order of the manufacturing processes is as follows: willeying, blending, teasing, scribbling, carding, forming, harden ing, milling, carbonizing (if not already carbonized in the wool state), dyeing, tentering and finishing.
The scribbled wool is fed on to the carder, the sliver from which is run full width (5o to 8oin.) onto the "former" (which consists of a frame carrying an endless cloth of about 4oyd. long) until a soft batt or lap has been built up sliver by sliver to required thickness and weight.
The soft batt is then hardened. There are two kinds of harden ing machines—the roller hardner and the plate hardner. The roller hardner consists of a frame carrying steam-heated rollers on which runs an endless heavy wet cloth. Working over this cloth are a further number of wood rollers, having an oscillating movement derived from a side shaft with eccentrics. The soft batt is carried through the hardner by the wet cloth, and the steam which is gen erated by the contact of the wet cloth and the steam-heated roll ers, passes through the soft batt, while at the same time the oscil lating wooden rollers gradually felt the fibres together till the felt is sufficiently strong to stand the following milling process.
The plate hardner consists of a bottom steam chest with a wet cloth running over it and a top plate, which has a vibratory move ment, which can be raised and lowered, in order that the felt may be passed through. All the motions are automatic and the time and throw of the vibratory movement can be varied according to the thickness of the felt being hardened. By careful splicings two or more batts may be hardened together, end to end, into one long piece, or they may be hardened together side by side, thus form ing one piece of double width, or two or more batts may be hard ened together, one on top of the other, this making one thick piece. In the hardening process, the felting which takes place affects the thickness very considerably, and not the area; but in the subse quent milling process the area is affected very considerably, some times as much as 5o%, but the thickness is not altered much.
The hardened felt not having any warp or weft is still compara tively weak, and must be handled very carefully in the preliminary milling stages, or damaged places will occur. The hardened felt is now brought in contact with a fulling or milling agent, such as soap, weak acid or weak alkali. The first milling is usually done in the fulling stock, where the felt cloth is continually hammered, and the fibres become interlocked closer and closer together until the required length and width have been obtained, and a cloth of considerable strength produced. The milling process may be fin ished in the fulling stock, or, according to the kind of felt being produced, it may be finished in the milling machine.
The following processes, viz., dyeing, tentering and finishing, are similar to those used in woollen cloth manufacture, and so do not require to be further explained here.
Some of the uses to which felts are put are saddlery, seatings, carpets, surrounds and underfelts, table felts, shoe and slipper felts, mattress felts, chest preservers, shoulder pads, engineering and motor car felts, antivibration, heat insulating and sound dead ening felts, railway and shipbuilding felts, grinding and polishing felts for metal, marble and plate glass, packing felts, gun wad felts, piano and organ felts, filter felts, lithographic and printers' felts, felts for paper-making machines, etc.
Impregnated felts such as ship sheathing and roofing felts are not true felts. In this case a batt made from jute or flax waste is impregnated and held together with a waterproof solution, the basis of which is tar bitumen or resin. Some roofing felts are made from thick porous paper impregnated with a waterproof solution.
Hat felts may be divided into two classes, viz., those made from wool and fur respectively. Wool "bodies" used for the lower qual ity hats are manufactured in the same way as ordinary felts, but the "shape" upon which the film issuing from the carder is built up takes the form of a double cone and thus approximates to the shape of the two hats ultimately formed. The shape is further controlled and developed in the fulling or felting operation. In the fur hat felts an air-blast is employed to carry the finely separ ated fibres on to the shape required, upon which shape the fibres are held in position by suction until the required thickness is ob tained. The structure is then hand hardened, further developed and "stiffened," i.e., impregnated with certain stiffening agents according to requirements. If desirable the exterior fibres blown on to any shape may be of a different material from the body fabric. (A. F. B.)