Weaves cotton into a stiff diagonal twill that fades exactly where your body bends it.
Also called: jean fabric, stretch denim
The basics
What to know about denim
Denim is a cotton cloth defined by its weave, not by its color. The crosswise yarn passes under three lengthwise yarns and over one, a 3 by 1 twill. That weave means the lengthwise yarns dominate the face, and the diagonal ridges run corner to corner. Only those lengthwise yarns take indigo dye, and the crosswise yarns stay white, which is why the inside of a blue jean is pale.
Weight predicts how a pair will feel before you try it on. Denim is sold in ounces per square yard. Around 8 ounces wears like a shirt, and 11 to 13 ounces covers most jeans. Anything past 14 ounces stands up on its own for the first month. Heavier cloth takes longer to break in and repays that with years of extra life.
Elastane reshaped the category. One to 2 percent keeps the cotton character while adding enough give to sit down in a slim leg. Above roughly 3 percent the cloth clings, bags behind the knee by evening, and stops fading in the sharp lines that make a worn pair look personal.
Indigo coats the outside of each yarn instead of soaking through it. That single fact drives the care rules. Fresh dye rubs off dry onto pale seats and shoes for the first several wears. It also wears away from the high points to create the fades. Wash cold, inside out and rarely. Hot water and a tumble dryer both pull dye, and untreated denim can shrink as much as 10 percent. Sanforized on the label means the mill did that shrinking for you, and movement stays near 1 to 3 percent.
In photos
Denim on real products
See this option on different products. Open a photo for a larger view, or select the name to read its guide.
Cotton is spun into two kinds of yarn for denim. The lengthwise warp yarn is rope dyed. Bundles of yarn dip repeatedly into an indigo bath. Each dip lays down a layer that turns blue as it oxidizes in the air between dips. Indigo never bonds into the fiber core, it only coats the surface, and that is the entire reason denim fades the way it does.
The dyed warp is coated in starch for strength and loaded onto a loom, where undyed weft yarn crosses it in the 3 by 1 twill. Wide modern looms produce most denim. Narrow shuttle looms produce selvedge denim, named for the tightly finished edge that comes off a machine only about a meter across. That edge is why selvedge costs more per yard. Finishing then sanforizes, singes or washes the cloth before cutting.
Best for
When it works well
Hard daily wear suits it, because a 12 ounce twill resists abrasion far better than a plain weave of the same fiber.
Jackets and jeans keep their structure in it, as stiff cloth holds a shape between wears instead of collapsing.
Anyone who wants clothing to record their life gets that here, since the fades form where your own body creases the cloth.
Low laundry routines become a feature rather than a shortcut, because denim ages best on a cold wash every ten wears or so.
Cold windy days are easier in it, as a dense twill blocks far more wind than an open weave.
