• Felt



Felt? What is felt? We often hear questions about felt. What it actually is and how it is made. When discussing it in English felt as a word is already a mystery. Well, lets start demystifying it.

What we know of it? Most of us can relate to felts shoes, slippers and boots. Those all time favourites of felt items. The modern version of felts shoes gives also an impression of felt’s versatility. If you desire to see beyond regular slippers – check the collections of Huopaliike Lahtinen and Alhon Huopatehdas. There you will have an idea.

Let’s talk some more of felt. Here at KH Felts in Koskenpää we have selections of some hundred of items. As felt can be produced from several types of fibres – both organic (natural) fibres as well as from man-made (synthetic) fibres – and felt can be hand-made as well as intrustrially manufactured.

When talking of hand-made felts and artesan skills, we talk of felting. When talking about the industrial production, we just refer it as the manufacturing process – as it is far more complex. Hand-made felts are mostly done solely from wool fibres.

What comes to industrial manufacturing of felt – we here at KH Felts lean on to the two basic methods – needling and fulling. Wool felts are fulled, the process requirements for felting process are closer to the hand-felting – it requires moisture, heat and movement.

Needle-felting instead is based on dry-felting. The small barbs of the needle stick into the scales on the fibre surface and the movement allows the fibres to mix with one another and form a fiber texture.This is how most of felt textiles are manufactured. Needle-felting has enabled the versatile use of different fibre types and the diversity in the industrial felt production.

The wool felts in our KH Felts selection are manufactured by fulling and most of the synthetic felts are manufactured by needle-felting. Yet there are fibre mixtures used in the fulled wool felts, but the amount of wool fibres is still high. The KH Sealing strip is manufactured by needle-felting – it is actually a low density polypropylene felt.

Few Words about Wool

The following paragraphs will hopefully enlighten the good and generally acknowledged qualities of wool. The despriction of wool fibre qualities is an abstract from the bachelor thesis of Iina Jokela (2006, pages 5-6):

Wool Fibre Qualities

The flexibility of the molecular chain of the fibre creates the elastic nature of wool. Its natural tendency for elasticity is greater than for any other fibre. Wool has unique ability to revert to its original shape, ability that greatly affects the comfortness that wool textiles have. Wool clothes adapt to body shape and allow freedom of movement for the user. In carpet textures the wool fibres preserve their elasticity for years.

In cold weather the fibres of the wool garment absorb the moisture keeping the skin dry. The dry layer of air between the skin and the garment, as well as the air pockets of the wool texture, help to keep the body warm. In hot air the absorption process keeps the skin cool. Sweating being the natural cooling process for body temperature. The wool cell absorbs the body steam and helps to reduce the body temperature.

Wool has the ability to resist static electricity. Thanks to the ability to absorb moisture from surrounding air the accumulation of static electricity reduces. This also results the dirt-repellent nature of wool. As the wool does not accumulate static electricity it neither collects dust from air. In addition – the scales on the outer layer together with the crimps of the fibre block the dirt from entering the fibre surface.

Wool is also naturally fire-safe material, which doesn’t require special treatments. Wool is non-flammable and difficult to enlighten. It does not keep the flame, when the heat source is removed. Wool doesn’t give any burning fluids whilst burning and it has excellent ability for suffocation.

Synthetic Felts

The needle-felted synthetic felts are most often made of white polyester fibres. Other common fiber types are polypropylene and viscose, which is cellulose-based yarn, organic yet not natural, a highly manipulated fibre.

The selections of synthetic felts is extremely versatile and the production can be taylored to specific needs. Synthetic felts are commonly used in autoimotive and steel industry and the felts are suitable for thousands of applications. Common use is as conveyors, sweepers, filters and gaskets. The costs for synthetic felts vary greatly from modest priced polyester felts to high-priced aramid and melamine felts.

The industrial felts are manufactured with very different types of characteristics such as resistance to heat, non-flammability, extreme abrasion resistance or even with anti-bacterial treatment. These characteristics are formed from different types of fibre mixtures as well as with chemical treatments. Most common treatments are oil- and dirt-repellent treatment and the use of resins for creating hard felts. The elongation and tensile strenght can be enforced with different type of scrims.

About fibres

Polyester is popular fibre not only due to its general qualities but also due to its good availability and modest pricing. Its characteristics include a working temperature of 100 degrees of Celsius. Polypropylene is fibre with better chemical resistance although its working area is lower than with polyester. Polypropylene also has better availability in colours.

For more complex operational environments and applications felts with special fibres and fibre mixtures are used. Special fibres such as meta- and para-aramides and melamine fibres. These fibres have qualities for high working temperatures and high abrasion resistance classes, fire-proof and cut-proof characteristics. Applications can be found in steel refining processes as well as in targets with high standards for personal and fire safety.