What Is Felt?

How is felt made?

Felt is made by laying loose fibres into a mat and then working that mat with heat, moisture and friction until the fibres interlock into a solid sheet. Britannica describes the main stages for industrial wool felt.

1. Preparing. The fibres are cleaned, blended and carded into a web.
2. Laying up. Layers of web are built up into batts.
3. Hardening. The moistened batts are drawn between aprons across a steam chamber, which starts the fibres interlocking.
4. Fulling. The felt is worked further until its area shrinks by as much as 50 per cent.

Other fibres will not felt alone, but they can be mixed with wool, which acts as a carrier. Britannica notes that as little as 10 per cent wool in a blend can be enough to produce a felt. CAMEO, the materials database of the Museum of Fine Arts, Boston, draws the line more widely: it describes felts of cotton, rayon and synthetic fibres such as polyester and acrylic, matted by mechanical, chemical or thermal processes. Britannica’s account covers only wool, fur and hair felts.

Hat felts and the mercury problem

Wool hat bodies are formed from a narrow carded web wound onto an egg-shaped mandrel. Fur felt hats use beaver, hare and rabbit fur. To give the fur its full felting power, hatters treated it with chemicals, including mercury, in a step called carroting. Britannica records that the mercury fumes released during felting led to an especially high rate of mercury poisoning among hat workers.

Myth check: a popular story ties the phrase “mad as a hatter” to this poisoning. The Online Etymology Dictionary dates the phrase to 1829, calls it originally Scottish and traces “hatter” in it to possible Scots and Norse word roots. It does not mention mercury.

Origins and living traditions

No one knows when felt was first made. The oldest known samples, wool felt excavated in Turkey, date to at least 6500 BCE, according to CAMEO. Nomadic peoples of north central Asia still make felt by traditional methods for clothing and shelter.

In Kyrgyzstan, felt carpets are among the foremost arts of the Kyrgyz people. The two kinds, ala-kiyiz and shyrdak, warmed and decorated nomadic homes, and the skill passes, as a rule, from older women in rural and mountain areas to younger women in their families. UNESCO notes that the meaning of their ornament and the ceremonies of making them give Kyrgyz people “a sense of identity and continuity”. It inscribed the practice on its List of Intangible Cultural Heritage in Need of Urgent Safeguarding in 2012, reporting that ala-kiyiz have practically disappeared from Kyrgyz homes and that shyrdaks are under serious threat of being lost.

What are the properties of felt?

Felt insulates well against temperature and noise, and its other qualities depend mainly on its fibre. CAMEO compares the common types as follows.

Britannica lists felt’s uses as wicking, absorption, vibration isolation, insulation, padding and packaging, polishing, sealing and gasketing, as well as apparel and decoration. CAMEO adds hats, blankets and rugs.

How is felt graded or measured?

Manufactured wool felt is described by its format, thickness, wool content and fulling shrinkage; Britannica gives these figures.

Fulling is also applied to woven or knitted wool, which it thickens and compacts, shrinking it by 10–25 per cent in both directions into a smooth, light, warm and relatively weatherproof fabric. Loden, first produced in Austria in the 16th century, is a common example. A fulled cloth still has a woven or knitted structure underneath; true felt has none.

How does felt appear on a clothing label?

Felt is a construction, not a fibre, so a US label on a felt garment names the fibres it contains, by generic name and percentage by weight in descending order, and also gives the country of origin and the identity of the manufacturer or another business.

Wool felt under US rules

• The FTC allows “wool” for fibre from the fleece of sheep or lambs and for the hair of the Angora goat (mohair), Cashmere goat, camel, alpaca, llama and vicuña.
• Wool or recycled wool must be disclosed by name and percentage, even when it makes up less than 5 per cent of the product.
• Reclaimed fibre must be called “recycled wool”: wool returned to a fibrous state after being woven, knitted or felted into a wool product.
• A fibre trademark may appear only next to the generic fibre name.

Felt hats

The US Textile Act does not cover headwear, including hats and caps. Wool hats, however, are covered by the FTC’s Wool Rules, so a wool felt hat sold in the US still needs its wool content declared.

What the percentage tells you

Since 10 per cent wool can be enough to make felt, trust the percentage over the words “wool felt”. The FTC’s 3 per cent tolerance on fibre content does not apply to labels such as “100% Wool” or “All Wool”.

How do you tell good felt from poor felt?

Judge felt by its fibre content, then check surface, water resistance and wear against how each fibre behaves.

1. Read the fibre line. On a US-sold garment or hat, look for the word “wool” with a percentage. A brand or trade name without a generic fibre name beside it does not meet FTC rules.
2. Look at the surface in daylight. Wool felt is soft and matte. A slight shine with a fuzzy or hard surface matches CAMEO’s description of acrylic felt; a silky sheen suggests rayon.
3. Drop water on a hidden spot. Wool felt is water-repellent and acrylic felt is not, so a drop that soaks straight in suggests a fibre other than wool. The test cannot separate wool from polyester or polypropylene, which also resist water.
4. Rub and check for pills. Wool felt is very durable and pill-resistant. Heavy pilling on a nearly new piece points to a less durable fibre.
5. Check edges and stress points. Rayon felt is prone to tearing, so torn or split corners on a barely used item are a warning.
6. Check second-hand wool felt for insect damage. Wool felt attracts insects.

Red flags: a wool felt hat sold in the US with no wool percentage; “100% wool” on a piece with a slightly shiny, fuzzy or hard surface, which matches CAMEO’s description of acrylic felt, not wool.

How do you care for felt?

Care for wool felt by avoiding the heat, moisture and friction that made it, because the same conditions can keep shrinking and compacting it.

• Keep it dry. Wool felt degrades in warm, moist conditions.
• Do not rub when wet. Rubbing and squeezing wet, warm wool is exactly how fulling shrinks cloth by 10–25 per cent.
• Protect it from insects. Check stored wool felt regularly, since it attracts insects.
• Keep synthetics away from heat and sun. Polyester and polypropylene felts are sensitive to UV light and heat; acrylic felt to UV light and moisture.

Is felt sustainable?

Whether felt is a lower-impact choice depends on its fibre and where that fibre came from.

• Recycled content. CAMEO notes that felt is occasionally made from rags and recycled paper. In the US, wool reclaimed from earlier products must be labelled “recycled wool”, so the label tells you whether it is present.
• Synthetic felts. Felt is also made from synthetic fibres such as acrylic, polyester and polypropylene.
• Craft heritage. UNESCO lists cheap synthetic carpets, scarce and poor-quality raw materials and a declining number of practitioners, most of them over 40, among the threats to Kyrgyz felt carpet-making.

For the wider picture, see sustainable fashion.