Felt

Felt, fabric built up by the interlocking of unspun wool fibers occasionally blended with small quantities of vegetable and synthetic fibers. True felt can only be made of fibers that are covered with minute, flexible, barblike scales, which allow the fibers to interlock when felted. Wool fibers, such as most sheep's fleece, are covered with well-defined scale structures; hair with poor scale definition, such as human hair, is not likely to felt.

When felts are intentionally manufactured, fibers and scales are made pliable by heat. Moisture and, sometimes, soap are used to lubricate as well as soften. The fibers are entangled or matted by agitation such as by rubbing. By the modern method, wool is cleansed, disentangled, and reassembled into thin webs, which are then piled in successive layers to a thickness required for the finished piece. The prepared fibers are then condensed on a flatbed press. The lower plate of the press is heated as the upper plate oscillates, causing the fibers to interlock. The felt is then fulled, or shrunk, to compress the fibers, which intertwine to form a loose fabric that, after further shrinking, becomes dense and durable.

Fibers used with wool in the manufacture of felt include vegetable fibers, such as cotton, kapok, ramie, and jute, and synthetic fibers, such as rayon and nylon. However, as the percentage of wool is decreased, the propensity to felt is proportionately decreased. In fact, blending wools with other fibers is one means of reducing undesired felting, such as in wool knitted goods that are designed to be machine launderable. Other methods to prevent felting are chemical removal of scales; elimination of the use of tight yarn and fabric constructions, which restrict freedom of fiber movement; and the use of resin coatings, which bind fibers together.

Felt making is one of the primitive arts, antedating weaving. Since the Industrial Revolution, mechanical operations have superseded hand methods, but the principle of felt making has not changed. Finished felts are produced in a range of consistencies from soft cloth to a dense sheet. Roll felts are finished and dyed; sheet felts are sawed, drilled, and turned, like wood, to form polishing wheels and various mechanical parts.

Wool felt and other nonwoven fabrics are used in inking pads for automatic printers; in vibration dampeners for machinery; as soundproofing; and for polishing glass, granite, and some metals. Oil-soaked felt pads are used to lubricate machinery. The resilience of felt makes it the only substance suitable for dampers on pianos and other musical instruments. Wool felt is widely used in making hats and other types of clothing.

Woven or knitted wool is felted in a controlled process called fulling or milling. Under extreme conditions, the fabric condenses into a dense, matted structure, making it difficult to identify the original yarns or construction. These felts are often finished by napping or brushing to make them stronger and more resistant to tearing. Examples of heavily fulled fabrics are loden and melton cloth used for outerwear.

Various fabrics of feltlike consistency are distinguished by compound names. For example, the name fur felt identifies fiber origin, and terms such as needle punched, blown, woven, stitched, or quilted felts refer to the manufacturing process. In the manufacture of felt for some applications—roofing felt, papermakers felt—true felting action is not usually employed.