Production of American felts is governed by exacting specifications, from selection of the stock through each critical step in the manufacturing process.
Material sources comprise many different origins and grades of wool, as numerous fibres having less favorable felting properties, but desirable values in other respects.
Various supplementary treatments greatly enlarge the range of finished products, leading to the addition of new adaptations of felt in a number of different ways.
Exacting specifications and controls govern felt making at the mills of the American Felt Company, from the sampling and grading of the raw materials, through every step in manufacture- including conditioning in the card-rooms, the strange and baffling chemistry of the dye-house, and even the speed of the rolls which govern the rate of drying.
True felt may be composed of exclusively wool and for a great many uses only wool enters into its composition. But such is the agglomerating property of this material that it is capable of incorporating various other fibres, which do not as readily felt by themselves, or which perhaps do not felt at all. Advantage is taken of this material that it is capable of incorporating various other fibres, which do not as readily felt by themselves, or which perhaps do not felt at all. Advantage is taken of this ability of wool to serve as a construction agency to multiple the properties which are attributable to felted wool alone. Thus, material of an especially soft texture may be produced by mixing wool and cotton. A light-weight, thermal-acoustical lining is produced by felting together kapok with wool and cotton. A particularly hard and durable felt, excellent for use as an abrasive carrier for use in polishing silver-plated tableware, is composed of a mixture of cotton and goat hair with wool. Extended blends, of which these represent a few of a great many possible examples, include a wide range of fibres, thereby multiplying the manufacturer’s in raw materials and also enlarging the range of materials which may be produced, since such mixed compositions introduce many characteristics beyond the wide range that is incident with wool alone.
Within the framework of felt composed exclusively of wool are many technicalities, requiring an unusual combination of experience and scientific control in order to achieve quantity production within the close limits of standard specifications. The best felting wools are selected primarily for their occurrence. However, beyond the source of the wool, are many fine distinctions which must be observed in the selection of wool appropriate for various felting purposes. The breed of the herd, the range and its varying conditions from season to season and even the time of shearing, all have a bearing on the character of the wool clip. Other distinctions depend on the variations in the fleece, which customarily yields at least eight different grades of fibre. Its condition, and the consequent treatment required in scouring, is another important factor. The net result of these and other elements is that the stock with which felting begins is necessarily a blend of fibres from different sources, whose composition determines the processing details.
Moreover, since textile processes in general are physical rather than chemical, it follows that wool which has been previously worked and subsequently separated into a loose, fibrous condition, is readily adaptable for inclusion in felts for certain purposes. One source of importance from the economic standpoint is the nails, or shorter, kinkier fibres combed from wool in the manufacture of worsted yarns. Another is garneted stock, which is the name given to carded stock derived from yarns, mill-ends and tailor’s clipping of woolen cloth. Considering the variable quality of the natural fibres, as well the fact that fibres of different origins are often combined in wool felts, it follows that the mechanical mixing of the raw stock is quite as important as their selection and proportioning. Yet, notwithstanding its critical nature, the operation is relatively simple.
The stock of various grades forming the mix in any given instance is weighed out to obtain the specified proportions, then piled in layers on the mixing room floor until a batch had been completed. Lifted by vertical cuts from the stock pile, the mix is then fed into the “mixing picker,” which cuts through and shuffles the fibres in what is really a sort of dry stirring operation. This process must be repeated until all cotts and tufts have been separated and the stock is thoroughly blended. In some instances the mix is blown from the picker in a turbulent, fluffy cloud, where the fibres are further separated and swirl into the bin in a loose and indistinguishably mixed mass.
Carding, which follows, is similar in methods and equipment to the textile operation of the same name, except that the webs from several machines may be fed onto a single endless blanket, the alternate layers being crossed to provide transverse strength. For hardening, batts from the cards are unrolled between blankets on a long table, sprinkled to desired degree of saturation, then steamed as the material is drawn over the bed of the press. As each section of material is brought into action it is drawn under the platen, a heavily weighted, cast-iron plate. The platen is then lowered onto the bed and driven in a rapid, oscillating motion for a definite length of time with strokes of predetermined length, after which it is raised while a new section of the batt is brought into working position.
Hardened felt from the back end of the table is allowed to drain and season until an equilibrium has been reached, then taken to the fulling mill, which has a curved front and is equipped with pendulum hammers having a stepped face. Folded and rolled, the material to be made firm through felting, is hammered in the mill in a steaming, moist state, the respective contours of hammer and tub being such that at each stroke the felting mass is kneaded and turned to expose a new side at the next thrusts of the hammer. Periodically the felt is removed from the mill, unrolled and refolded, to prevent it from felting on itself, and also to control the fulling action in respect to the shrinkage in length and breadth.
Felting runs may continue for only a few minutes on some of the softer materials, or continue for hours when a harder construction is being fabricated. Cleansing of the felt before finishing follows ordinary textile practice with few variations. Dyeing follows established techniques. Treatment by impregnation for various purposes are also interpolated prior to the final finishing. Felt may be treated with oils, waxes, resins and asphalt, to render it water-repellent; sized for increased stiffness; flameproofed, mildewproofed or mothproofed, to specifications. All such treatments involve the coating of the fibres or filling of the voids in thefelt with fluids, including salts in volatile solvents. They are readily preformed while the material is in a warm, moist and chemically neutral state. Therefore they may be added to the manufacturing process at relatively low expense.
On the other hand, their effect may be to alter the natural character of the material very considerably, thereby greatly extending its range of usefulness, or perhaps fitting it for applications to which it would be unsuited otherwise. Illustrative of this principle, is the coating of cut felt parts with latex, reclaimed rubber or plastic compounds, thereby producing effective alternates for rubber and synthetic materials. The traditional method of drying felt in the piece is on an extensible “tenter frame” on which the edges are impaled and which is then run into a tempered atmosphere for the drying.
A modern equivalent, permitting continuous operation, by stitching the pieces end to end, is the chain dryer, which stretches and conveys the material through the hot air oven simultaneously. Still another development in drying which, like many others, was developed by American Felt Company engineers, makes use of mills combines direct radiation with conduction heating and used in the production of sized material. Such material, when dried by conventional means tends to become caked with size on the outside, due to the too rapid drying action at surface, when surface drying is combined with infra-red radiation, moisture is expelled by through heating from the inside out. Moisture does not become imprisoned within the material, as in drying by conduction or convention. Finishing methods depend on the quality of the felt and its intended use.
A smooth, pliable material, having the touch of the finest broadcloth, and much the same appearance, is processed by brushing to raise a nap, shearing on both sides to remove protruding fibres and ironing between hot rollers. The process also controls the thickness, which is limited by tolerance commonly expressed in the decimal of an inch. The harder qualities of felt are often run through grinders, machines which smooth the surfaces to a true level. This statement indicates in some degree the tough nature of material. The processing of felt from start to finish requires about five to ten days, depending on hardness, from the raw stock bale to the shipping department. As has been explained, the operations required are essentially the same for all grades; however, quantity production, plus the demand for many different qualities in a business like that of the American Felt Company, produces rather more diversification than might be expected. Where one department is devoted to surgical felts, for example, another may be specializing on hard felts for polishing glass; a third on piano hammer felt, while others are turning out more varied products, no two successive orders being for precisely the same material.
All told, there are perhaps 150 different kinds of wool felt, as distinguished by fibre composition and general treatment. Considering physical properties, variations in weights and colors, this amounts to at least one thousand merchandise numbers. These varied materials normally are distributed into so many different channels of commerce and industry that the seasonal factor is very well counterbalanced by overlapping requirements from different sources. Because it covers the entire field of felt products, American’s business is very well stabilized. It is continually in the market for raw materials, but centralized purchasing and long-range policies permit advantageous operation. American felts are in demand from one year’s end to the other from its many customer sources distributed along more than one hundred industrial channels.