What Is Denim?

Where does denim come from?

The word denim comes from the French serge de Nîmes, “serge of Nîmes”, after the town in southern France, but the cotton cloth we now call denim is documented much later, in 19th-century America. The Online Etymology Dictionary dates the word in English to the 1690s, when it named a kind of serge, and finds the sense of a coarse, coloured, twilled cotton cloth in American English by 1850. Encyclopaedia Britannica says only that the name is said to derive from serge de Nîmes.

Neither source says the 17th-century Nîmes cloth was the same fabric as modern denim, so treat a direct line from Nîmes to jeans with caution.

The Museum at FIT holds American trousers from about 1840 patched with denim, a rare precursor of the blue jean made some 30 years before Levi Strauss & Co.’s 1873 patent. Durability made denim a work cloth, notably in Levi Strauss & Co.’s clothing for fortune hunters of the California gold rush. By the start of the 20th century, the museum notes, it was used for clothing from prison garb to naval uniforms. Britannica notes that the same durability made denim serviceable for leisure wear in the late 20th century, though the museum also shows a denim leisure shirt from about 1940.

How is denim made?

Denim is made by dyeing the warp yarns (the lengthwise threads) blue, leaving the weft yarns (the crosswise threads) white, and weaving them as a warp-faced twill. Britannica calls it yarn-dyed, coloured before weaving, and mill-finished.

1. Fibre. Britannica says denim is usually all cotton, though a considerable amount is a cotton-synthetic blend.
2. Dyeing the warp. The Museum at FIT describes the traditional method, rope dyeing: groups of warp threads run through vats of indigo, then hang in the air, a step called skying. A deep blue needs the dye built up in several coats.
3. Weaving. The warp-faced twill puts the blue on the face and the white weft on the reverse.
4. Selvedge or wide loom. Selvedge denim is woven on shuttle looms that make cloth only about 29 inches wide, with a strip of white threads along each edge. The museum says most such looms in use today date to the 1940s or earlier.

Faded and worn looks are finishes added later, such as stone wash, acid wash and distressed denim.

What are the properties of denim?

Denim is a durable, two-toned cloth: strong enough for workwear, blue on the face, paler on the back, and can be stiff.

• Durability: Britannica notes its long use for overalls and trousers for heavy labour.
• Handle: sturdy and can be stiff, unlike chambray’s softer, lighter feel, according to Cotton Incorporated, the US cotton industry body.
• Range: the Museum at FIT notes that denim now comes in many colours and weights, and that some versions include stretch fibres in the weave.

What is the difference between denim and chambray?

Denim is a twill and chambray is a plain weave: both pair a coloured warp with a white weft, but denim is heavier and stiffer and shows a diagonal, while chambray is lighter, thinner and softer.

Denim is also distinct from what is made of it: jeans are trousers made from it, and a denim jacket is another garment cut from the same cloth.

How is denim graded or measured?

Denim has no official grade: it is identified by its structure and judged by its fibre, dyeing and weaving. It comes in many weights, but the label rules below cover fibre content, not weight or weave, so “denim” on a tag is a description, not a grade.

How does denim appear on a clothing label?

Denim is a cloth name, not a fibre name, so the required label lists fibres, such as “100% cotton”, rather than the word denim, under rules that differ by market.

United States

• The FTC requires fibre content, country of origin and the identity of the manufacturer or another responsible business; a registered identification number (RN) may replace the name.
• Fibres are listed by generic name and percentage by weight, in descending order. The stretch fibre may appear as “spandex” or by its ISO name, “elastane”.
• Fibres under 5% are generally grouped as “other fiber”. The exceptions include wool, which must always be named, and a fibre with a definite functional significance at that amount, such as spandex used for elasticity.
• A 3% tolerance applies to fibre percentages, but none applies when the label says the product is a single fibre: “100% cotton” must be exactly that.
• The label must stay securely attached until the product reaches the consumer but need not be permanent; care instructions, under a separate FTC rule, must be on a permanent label.

European Union

• Under Regulation (EU) No 1007/2011, only the fibre names in Annex I may be used, including “cotton” and “elastane”.
• Every constituent fibre must be named with its percentage by weight, in descending order.
• “100 %”, “pure” and “all” are reserved for products of one fibre, though up to 2% by weight of extraneous fibres is tolerated if technically unavoidable and not added routinely.

How do you tell good denim from poor denim?

Good denim shows its construction clearly and carries a complete label. Five checks:

1. Turn the garment inside out. The inside should be visibly paler than the face, because the white weft shows there. If both sides look alike, it is not classic blue denim with a white weft.
2. Look along the face in good light. Denim shows the diagonal of a twill. A fine grid of blue and white with no diagonal is a plain weave such as chambray.
3. Look at the cloth edges inside the seams. A strip of white threads along the edge of the cloth marks selvedge denim, woven on a narrow shuttle loom.
4. Read every fibre on the label. “100% cotton” in the US allows no tolerance. A stretch fibre may be named even below 5%, because elasticity counts as a functional use.
5. Check the rest of a US label. It should name the country of origin and the maker or an RN.

Red flags

• No fibre content anywhere on the garment or its tags, which both US and EU rules require.
• “Selvedge” claimed on a garment with no edge strip visible inside any seam.

How do you care for denim?

Follow the care label, then wash denim less often, in cold water, and dry it on a line, as Levi Strauss & Co. advises in its 2015 life-cycle assessment of a pair of 501 jeans.

• Wash less. Washing after every 10 wears instead of every 2 would cut energy use, climate impact and water intake by up to 80% in the study’s modelling.
• Use cold water. In the study’s US model, washing cold instead of warm would cut the non-renewable energy use of a pair’s lifetime washing by 21% and its climate impact by 24%.
• Line dry. In the same model, line drying instead of using a dryer would cut the non-renewable energy use of that laundering by 64% and its climate impact by 67%.

These are one company’s figures for one product made in 2012, offered by the study only as an example for that timeframe.

Is denim sustainable?

Denim is not sustainable or unsustainable as a category: in the one detailed study cited here, most of the impact sat in growing the cotton, making the cloth and washing the garment. Levi Strauss & Co.’s 2015 life-cycle assessment of a pair of 501 jeans, carried out with Industrial Ecology Consultants and panel-reviewed against ISO 14040 and 14044, found from cotton growing to disposal:

• Total: 3,781 litres of water consumed and 33.4 kg of CO₂-equivalent over the life of one pair.
• Fibre production: 68% of the water and 9% of the climate impact.
• Fabric production (spinning, dyeing, weaving and finishing): 6% of the water and 27% of the climate impact.
• Consumer care: 23% of the water and 37% of the climate impact.

Claims about the fibre, such as organic cotton, address the stage that used most of the water; how you wash and dry addresses the largest share of the climate impact. The word “sustainable” on a tag tells you neither.