Felt is a flat textile material made of randomly arranged fibres that are difficult to separate. As felt is not woven, sheep wool or animal hairs with a surface of overlapping scales are necessary in order for these fibres to ‘felt together’. Felt is formed by orienting wool/animal fibres in parallel and layering them under the influence of moisture, temperature, pressure and mechanical movement. This causes the fibres with these overlapping scales to hook together in a largely random manner.

Felt is produced from synthetic fibres (e.g. PES, PP, PA) and from plant fibres (hemp, jute, coconut) by needling (needle felt) or by compacting with water jets that are produced by a nozzle bar at high pressure (water-jet compacting). A chemical binding agent can also be used, which essentially sticks the fibres to one another.

Felt has a range of different material properties. The most important properties are:

• Elasticity: Felt is stretchable, elastic in response to pressure, and resilient too – which means that hardly any creases are ever formed.
• Insulation: Felt is noise-reducing, and also insulates against heat or cold. It also has a moisture-repellent component.
• Absorbency: This property allows felt to soak up liquids and release them again.
• Its cushioning behaviour also provides protection against mechanical loading.
• Flame-retardant behaviour: Felt is generally not flammable. Even if it is directly exposed to fire, felt will only char above around 300 degrees Celsius.