Manufacturing Process of Felt: History, Raw Materials and Methods
B.Sc. in Textile Science and Technology
Ahmadu Bello University, Nigeria
Most fabrics are either woven or knitted these days; with woven fabrics taking almost 60% of the total textiles and apparel. In reality, textile goes beyond woven and knitted fabrics. It actually starts from Felt. Felt is a material that requires neither the weaving technology, nor the sophisticated knitting technology. In this article, I will discuss history of felt fabric, raw materials, methods and manufacturing process of felt.
Felt may be the oldest fabric known to man; it predates both weaving and knitting. Since felt is not woven and does not require a loom for its production, ancient man made it rather easily. Some of the ancient felt remain were found in the frozen tomb of nomadic horsemen in the Siberian Tiai mountains and date to around 700BC. These tribes made clothing, saddles and tents from felt. Legends have it that during the Middle Ages, St. Clement who was to become the fourth Bishop of Rome, discovered the process of felt making by accident. It is said stuffed his sandals with tow (short flax or linen fibers) in order to make them more comfortable. St. Clement discovered that the combination of moisture from perspiration and ground dampness coupled with pressure from his feet matted these tow fibers together and produced a cloth. After becoming a Bishop, he set-up a group of workers to develop felting operations, this made him the patron saint for hat makers, who extensively utilize felt to this day.
Manufacturing Methods of Felt:
Basically, there are two methods of manufacturing felt fabrics:
- Wet felting (traditional felting)
- Needle-felting (Dry felting)
A. Wet Felting:
This process uses the inherent nature of wool and other animal hairs, because the fibers have scale on them which are directional and the hairs have kinks in them. It is the combination of these properties that reacts to the stimulation of friction and causes the phenomenon known as felting. It tends to work well with wool fibers as their scales, when aggravated, curl and bond together to form cloth.
Wet fitted fabrics are produced from wool, which grips and mats easily, and a synthetic fiber that gives the felt some resilience and longerity. Synthetics cannot be turned into felt by themselves (using wet felting) but can be felted if they combine with wool. Typical fiber combination include; wool and polyester or wool and nylon.
Cheaper felt (artificial felt) if produced using the wet method, has a minimum of 30% of wool fibers combine with other artificial fibers, this is the minimum required to hold a fabric together with the fibers alone.
Other raw materials used include; steam, sulphuric acid (used in the thickening process) and soda ash (sodium chloride) which is used to neutralizes the sulphuric acid.
Cleaning, opening and blending process:
1. The fibers (animal wool) contain a lot of fats and are thoroughly cleaned and made free of fats and dirt by scouring process.
2. Since some felts uses more than one type of fiber, the cleaned fibers must be mixed and blended together before any processing begins. Usually, bale openers are used to accomplish this purpose.
3. These blended fibers are now passed into a carding machine using hopper feeders. This makes the fibers parallel to one another and delivers them in web form. At least two carding machines (carding cycles) are employed by passing the first web (through a transporter) to a second machine; this produces a new web which is thicker and fully carded.
4. The stuff has to be distributed as evenly and uniformly as possible both horizontally and longitudinally on the actual web makers.
5. Several different web are combined (sandwich laid) to create one thick web. Four layers of web considered a standard single roll, sometimes referred to as a batt. Batts are layered in order to create different thicknesses of felt.
The basic rule is the quality of nonwoven bounded fabrics such as felt can only be as good as that of the fiber web or fleece the web has been made into. Since the carders are not equipped with any storage facilities, any mass fluctuation in the feed will reappear unchanged in the card web, and once the fleece has been formed it cannot in the course of further processing be made more even and the irregularities present often have a decidedly negative effect on the mechanical and physical properties such as strength fiter effect etc.
Manufacturing process of felt:
The batts for making felted material must be hardened or matted together in order to create thick, densely felted material; this is achieved through the process out line below:
1. The batts are subjected to heat and moisture by passing them through a steam table.
2. The wetted batts are fed into a plate-hardener that shrinks the width of the fabric. The plate-hardener consist of a large square flat bed with a large plate that drops down over the wetted hot batts, exerting pressure on the material and compressing it. At the same time, the plate-hardener oscillates from edge to edge further matting the fiber to a specific width. Alternatively, a roller hardening machine can be used; here the batts are pressed by rollers rather than by plates. From the hardening machine, the fabric (except cushioning and padding felt) is sent to a fulling mill, where it is shrunk up to 50% in both length and width.
3. The above batts are fed into a fuller or fulling machine, which shrinks the length to specific measurement. As it shrinks, the felt becomes denser. The batts are fed through a set of upper and lower steel rollers that are covered with hard rubber or plastic and are molded with treads much like a car tire, enabling them to move across the felt. The felt is continuously wetted with hot water and sulphuric acid solution. The upper rollers remain stationary as the lower rollers are moved upwards to put pressure on the fabric and push it against the upper rollers. All the rollers, (both upper and lower) move together forward and backward. The pressure, the acid, the hot water and the movement causes the batts to shrink in length, making the felt even denser. Example, a piece of felt that is 38 yards long may come out of the fuller at only 30 yards in length.
4. The wet felt has sulphuric acid residue and must be neutralize by running it into neutralizing tanks filled a sodium chloride (soda ash) and warm water solution. The speed of passage at this stage is carefully timed.
5. The neutralize felt is then run through a refueling machine in which heavy rollers run over the surface of the fabric one last time to smooth out any irregularities.
6. If felts are to be dyed, the wet pieces are taken to a dye bath and if otherwise, the washed felts are finished in several ways. Finishes include those designed to make the fabric water proof or moth proof. Then the product is finally passed to a calendering or tendering machine. The felt is roll up and sent to a centrifugal dryer that spins out the water, while other companies have huge dryers in which the felt is pinned in place on a dryer bed.
7. Once dry, some companies press or iron the felt to ensure consistent thickness. Some manufacturers use this ironing to make dense felt even denser as ironing can shrink it slightly.
8. The finishing step includes placing the felt on a gauging table in which the edges of the felt are neatly trimmed. The fabric is now ready for packing, labeling and selling.
B. Dry Felting (Needle-Felting):
A needle felted fabric is a nonwoven fabric made from webs or batts of fibers in which special barbed felting needles on an industrial felting machine are used. The barbs catch the scales on the fiber and push them through the layers of web, tangling them and binding them together. This needling action interlocks the fibers and hold the structure together much likes the wet felting process, and it’s popular for two-dimensional and three-dimensional felted work.
With needle felting, any fiber will work even man made fiber and hair. All other wholly artificial felts are actually needle-felts.
Manufacturing process of dry felt:
A web or batts of fiber are transported by a feeding device between upper and lower hole-plates. The bearded needles periodically penetrate through the holes in the plates and through the batts. In every stroke, the barbs of the needle seized fibers and pull the fibers through the web creating fiber bundle. As the needle withdraws, the batt is released and moves a small step towards take-off rolls.
The level of web densification is among others a function of the number of punches per unit area of the web, the number of needles in the needle board. Attainable frequency of the needle board determines the performance of the machine.
- Kent Page ‘Felted Fabric’ www.ehow.com Updated July, 2010
- NancyEvBryk production of felt fabric. www.madehow.com/volume-7/felt.html.
- Joseph, M.L. (1980). Essentials of Textiles. California State University, Northridge.
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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.