The Manufacturing process of Felt
A LITTLE BACKGROUND
It is no secret that nearly all textiles are woven; however, this is not the case for felt. Felt is one of the oldest fabrics known to man, and is manufactured from fur and/or fibers which are matted and compressed through pressure heat and moisture. There are some felts which are entirely synthetic (made from synthetic fibers such as acrylic) and often used as alternatives by those who prefer non-animal felt; the other is wool mixed with a synthetic. The synthetic makes the felt stronger and enhances its durability, hence, which type selected is largely dependent on the purpose it is intended to serve- industrial, designer, craft or technical usage.
At the same time, the manufacturing process remains the same regardless.
MANUFACTURING PROCESS OF WOOL
MIX AND BLENDING
Due to the fact that there are some felts which are made up of more than one type of fiber, they must be mixed and then blended to get a consistent composition before anything else is done. The unprocessed fibers are therefore placed into a large enough opener which contains a sizeable cylinder that is studded with steel nails. This cylinder then churns and mixes the fibers together to form a uniformed mass.
FIRST CARDING PROCESS
After a consistent mass of fibers is obtained, the process of carding must be carried out so that the fibers are parallel to each other. This is done with by using carding machines, which are large cylinders used to mat the fibers into a sort of web- hopper-feeders allow a mass of fiber having a specific weight to pass through the cylinders and create an unvarying web. The fibers are then carded (pulled by wires) until they are parallel.
SECOND CARDING PROCESS
Two carding machines are generally used in the manufacturing of felt with each web being refined as a new one is created. The purpose of the second machine is to make a new web which is thicker than the original and completely carded. To do this a conveyor or transporter feeds the webs from the first into the second machine.
CARDED WEB REMOVAL
There is a comb which removes and rolls up the carded web form the second carding machine. This removal can be done in two ways:
What is known as a cross-lapper can be used to roll the web perpendicularly- across the original direction of the fibers.
What is known as a Vlamir can be used. This will roll the web in a parallel direction.
COMBINING THE WEBS
At this point, every carded webs are combined. They are rolled up in groups of four in alternating directions which are based on the way they were rolled- using a vlamir or cross- lapped. These rolls of four layers are considered a single unit and known as a batt’. They are layered this way to produce different thicknesses or density.
After combination the batts must be matted or hardened together to create dense felted material. Firstly, the batts are subjected to both heat and moisture simultaneously by passing them through a steam table.
SHRINKING THE WIDTH
Then comes the process of shrinking separated batts down to length and width to make dense felt. Again, these batts are subjected to moisture and heat but also pressure as well. This is done by firstly placing wetted batts on a plate-hardener which is made up of a large flat, square bed and a huge plate which falls over the wet and hot batts. It compresses this material by applying pressure to it- this is done to shrink the width of the fabric. While the plate exerts pressure, it simultaneously moves from edge to edge to further matt the fiber to a specific width.
SHRINKING THE LENGTH
The length is then shrunk to a specified measurement by feeding the batt into what is called a fuller machine. The catch here is that while it shrinks the length, it increases its density by width. This process is accomplished by feeding the batts through a series of plastic or rubber covered upper and lower steam-rollers, with tyre-like treads that allow ease of movement across the batt. A mixture of water and sulphuric acid is used to continually wet the felt.
Note that the upper rollers are stationary while the lower rollers move upwards to apply pressure. At the same time, both rollers move forwards and backward combining pressure, acid and heat to shrink the length of the felt while increasing its density. That is to say that a piece of felt 34.7 m long will turn out fuller with a length of 24.7m.
NEUTRALIZING THE ACID AND SMOOTHING THE FABRIC
The acid is then neutralized by running it through tanks containing a solution of the carbonate soda ash along with warm water. This is a process which is carefully timed according to the length and width of the felt. The felt is then laced in a refulling machine one last time so that irregularities can be smoothed out.
Some companies dye their felt in a dye vat before drying. Felt for industrial purposes however, go straight to drying.
Some companies simply employ the usage of centrifugal dryers to spin the water out of their felt (similar to the mechanisms of a washing machine). Others pin their felts to a dryer bed or leave them to air dry by hanging or lying flat in a drying room.
After drying is complete most companies want to further guarantee consistency in the thickness and so they press of iron their felt. Some even go as far as using the ironing to increase fabric density as ironing sometimes decreases the length even further. The edges are then trimmed neatly by a gaging table after which the piece is ready to be packaged, labelled and shipped.
Once materials arrive quality control immediately begins with the checking of quality and weight. There are some companies that request that their wools be scoured and baled- how pure a bale it has is examined on arrival. There are a few other import quality control checks which are done under continuous monitoring. An important starting test is shrinking the felt to the required length and width. This is done by continuously monitoring the carded webs and when the shrinking of the batt has been completed weight, width, length, density and evenness are checked.
On completion of this process, inconsistencies such as surface unevenness and acidity can be detected. It is important to remember as mentioned before that acid baths are timed to batt dimensions. Any less or more time in the acid bath will ruin the felt. Checks against government standards are then carried out and anything less or more than the specified government standards mean that the felt cannot be placed on the market. The general specifications for felt are: 7.3 kg in density, 2.5cm thick, 91.4cm in width, 9.14cm in length and 7.3 kg in weight.
WASTE AND BYPRODUCTS
During the trimming process small pieces that are filled with grease and oil from the machinery used to process the felt are cut of and sent to the landfill as they are not reusable.
The demand for felt is constant due to extremely versatile attributes. While the civilian applications of felt are far too many to count or list here, it has military applications including boots, rockets, small ammunitions and helmets. Excess felt which is white in nature and contains no grease or oils have been found very useful when grounded, coloured and placed in aerosol cans. Its unique purpose is to be used as spray for covering bald spots and have been growing in popularity.