This section is from the "A Complete Dictionary of Dry Goods" book, by George S. Cole. Also available from Amazon: A complete dictionary of dry goods and history of silk, cotton, linen, wool and other fibrous substances,: Including a full explanation of the modern processes ... together with various useful tables.
Felt. Woolen cloth united without weaving. The word felt appears to have signified at a very early period a material formed of wool not woven, but compacted together, suitable for every form of garments. To felt or feltre is to form a matted tissue of wool or other short hair in which the fibres are so interlaced by their curls, and so closely united to one another by the almost imperceptible notches of their scaly coats as to form a consistence like that of thick cloth. The term "felting" is chiefly employed in the manufacture of hats, but the operation of thickening woolen cloth, by means of a fulling mill depends on the same principle. [See Fulling, Broadcloth]
All accounts of the discovery of the principle of felting are traditional, thus proving the extreme antiquity of felted materials. By one it is ascribed to Oriental shepherds; another attributes it to an early English monarch, who putting some wool into his shoes to keep his feet warm, found that the combined heat, pressure, and moisture had produced a new fabric. According to some writers, a monk on a pilgrimage, having used some carded wool in his sandals, found that the fibres, by long friction between the foot and the sandal had matted together so as to produce a firm texture resembling cloth. From this hint the manufacture is said to have originated. An old hatter informed the writer that in his youth an annual festival was held in honor of this saint on the 23d of November, and that in Ireland and other Roman Catholic countries, the hatters still hold their annual festival on St. Clement's day, the saint who is the reputed inventor of felt. Again, it is asserted that as wool will sometimes, though rarely, felt upon the back of the living animal, that this may have led to the natural process being observed and imitated. There is, in any case, no doubt as to the antiquity of the process. It was known among the Greeks; Pliny mentions that the Gauls of his day made a kind of felt which was so firm and strong that it would resist a sword cut, more particularly when vinegar was employed during manufacture. Saxon writers continually mention the fellen haets -hats of felt - then used by their people. The Turcomans are said to dwell even to this day in huts covered with black and white felt, which they make by treading with their feet the raw wool while it lies upon the ground; and hence it is suggested that some of the wanderers among the Crusaders might have brought the art from Asia to Europe.
The manufacture of felted materials, which are all non-shrinking, has of late years considerably improved since the microscope revealed the philosophy of the process, and thus indicated how alteration for the better might be affected. The secret of the felting of wool fibers has been a mystery in all ages, and until 1860 was at best only surmised. Upon this property alone depends the whole art of hatting and of felt making whether in sheets or otherwise, as well as the fulling of cloth and the shrinking of flannels, and all articles the material of which is made of wool, hair or fur. A few facts dependent upon the felting quality of hair will aid the illustration. When a hair is held by the root, and drawn through between the finger and thumb, it feels quite smooth, but when held by the top, a rough and tremulous motion is perceived. Again, place a hair three or four inches in length by the middle between the finger and thumb, and twirl it a few times, when the hair will be found to proceed toward one end, as the twirling and rubbing are continued, and invariably advancing root end foremost, whichever way the hair is placed between the fingers. If two hairs are used in this example, lay the root of one on the top of the other, and their respective motions will be doubly discernible. The cause of this singularity of hair and wool fibres will now be explained as explicitly and concisely as possible: The above mentioned phenomena are the result of that same long-hidden property, and which is nothing more than a certain covering, entirely surrounding the stem of every hair in the form of minute scales, so very minute, indeed, that it requires the aid of a very powerful microscope to enable the beholder to discern them, and even then but faintly. These scales, which cover thickly every filament of animal hair, wool, fur, etc. are thin and pointed, somewhat similar to the scales on a fish, and overlapping each other as do the shingles upon a house. The task of counting the number of these scales that cover the body of each hair is tedious and difficult, but it has frequently been successfully accomplished. On a single filament of merino wool, as many as 2,400 barbed scales, like teeth, projecting from the center stem have been counted in the space of an inch. On Saxony wool there were 2,700, while other wools were as low as 1860, and none were found to have so few as 1,000 to the inch. No vegetable fibre whatever, such as cotton, flax, hemp, etc., have any such appendage upon their fibres, consequently they can never, alone, become suitable material for felting purposes, every fibre being smooth from end to end in either direction, and in contradistinction to wool, which though equally smooth as the cotton one way, rebels triumphantly when irritated in the contrary direction, as already described.
The grand cause of that mysterious and curious operation called felting, fulling, milling, shrinking, thickening and solidifying of a fabric, whether of original loose wool, fur or other stuff, or of that spun into yarn and woven into cloth, is the presence of these scales. Till lately, the best posted mamufacturer and the investigating philosopher were equally at a loss to explain upon what principle such effects were produced. Take for instance, a handful of wet fur or wool, which is merely an assemblage of hairs; squeeze and press it, work it a little in the hand, and then observe the effect; for immediately upon pressing it a certain locomotion is thereby conferred upon every fibre of that assemblage, which is increased by every turn of position that is given to the body of wool. The rolling and pressing change the position of each fibre. A friction is produced upon every member composing the mass; a footing as it were is obtained from the scales of each, and the fur or wool being all bent or curled, a progressive motion goes on, interlacing each other in their travels, resulting in a compact, dense body which will challenge the goddess of patience to undo. Every hair has been traveling in its own direction, boring, warping, grasping, holding and twisting amongst its fellows like a collection of live worms.
The manufacture of felt was formerly accomplished entirely by hand. The first step in this operation was to mix in proper proportion the different kinds of wool or fur intended to form the fabric, and then by the vibratous strokes of the bowstring, to toss them up in the air, and to cause them to fall as regularly as possible on the table, spread and scattered. The workman then covered this layer, or "lap" of loose fibre with a piece of thick blanket cloth, slightly moistened. This he pressed with his hands, moving the hairs backward and forward in all directions. Thus the different fibers get interlaced, by their ends pursuing ever-tortuous paths; their traveling motion being always, however, root foremost. As the matting became denser, the hand-pressure was increased in order to overcome the increasing resistence of the solidifying fibres. A first thin sheet of soft spongy felt being thus formed, a second is condensed upon it in like manner, and then a third, until the requisite thickness was obtained. These different pieces were successfully brought together and disposed in a way suitable to the wished-for article, and united by continued dexterous pressure. Of late years, however, machinery has been invented for the manufacture of felt. In machine work, the first operation consists first of carding the wool out into exceedingly fine uniform gossamer-like laps. These laps, of the length and breadth of the web to be made, are laid one on top of another in number corresponding to the thickness desired in the finished article. The layer that is to appear on the face of the fabric is usually of finer texture than the body and the mass when ready for felting has the appearance of a huge sheet of cotton wadding. In this state the compound lap is passed between a series of opposite pressing rollers partly immersed in water, some of which are solid and heavy, and others hollow and heated internally by steam, imitating as nearly as possible the variable pressure of the human hand. In its progress the lap is not only squeezed between the rollers, but an oscillating motion being given to the upper series, it is at the same time submitted to a rubbing action, corresponding to the to-and-fro motion in the hand work, the result being that after a few hours in the machine it issues forth a dense, compact sheet of felt of uniform thickness. Felt so made is afterward dyed, printed, and otherwise finished by the ordinary processes applicable to woven tissues.
As has been noted, felt may be made of any kind of animal fur, wool, or hair, provided it be bent, crimped, or curled; for if straight as a bristle it would work out of the mass as readily as into it, and lose itself in the operation. Wool of any great length of staple, after being carded, is pressed and either clipped, cut or chopped into shorter lengths, which facilitates the rapid felting, and also improves the solidity of the felt that is produced. The felting of wool necessitates either a damp or wet process with the aid of heat, and the facility for thickening or solidifying is hastened by the application of soap to the mass of fibres under operation. Or the water may be mixed with acid for the same purpose, as either of these acts as a penetrating solvent upon the natural oil of the wool which still remains between the scales and the stem of the hair, thus baring the barbed points of the crusty scales, the better to catch and hold their grip upon each other. Oil or grease, on the contrary, when applied directly upon wool, covers up these minute scales,thereby preventing their hold upon each other and destroying their felting power, as is well known to all wool spinners, however little they may understand the real cause of its being so, further than the fact of giving to it a smooth, gliding effect, so necessary for the object of their business. In the carding and spinning of worsted, in which the object is as far as possible to prevent the fibre from felting, the mass of wool is always greased with lard that it may be more easily worked. [See Fulling]