Shop for good jeans and you quickly run into a wall of jargon. Selvedge, loomstate, sanforized, one washed, rope dyed, 21 ounce. These words matter, because they tell you how a pair will fit, shrink, feel and fade. This guide breaks them down in plain terms, using real examples from two makers that live and breathe the stuff: Iron Heart in Japan and Naked & Famous Denim in Canada.
What selvedge actually means
According to Iron Heart, the words selvage and selvedge are a corruption of "self edge" and have been in use since the 16th century. The selvedge is the self finished edge of a fabric. It keeps the cloth from unravelling or fraying, and it is a result of how the fabric is made.
On denim, that finished edge comes from the loom. Iron Heart explains that selvedge denim is created on a shuttle loom, and that the action of the shuttle is what produces the finished edge. The company contrasts this with fabric woven on projectile looms, a different type of machine that does not give denim that self finished edge.
Turn up the cuff on a pair of selvedge jeans and you will see the edge running along the outseam, usually with a colored line. That line is called the selvedge ID. Iron Heart uses a traditional red line almost exclusively, while other brands vary the color from cut to cut.
Is selvedge always better?
Not automatically. Iron Heart is refreshingly honest about this. It says selvedge is widely seen as superior in the denim community, but that this is no longer always the case. The things that matter most are the quality of the cotton, the design of the fabric, the type of loom and the skill of the weaver. A selvedge fabric made without those can be mediocre, and a fabric woven on a projectile loom with them can beat many selvedge cloths.
The company also points out that the colored ID itself says nothing about quality. Selvedge denim that hides its ID is still selvedge denim. So treat the red line as a nice detail, not a guarantee.
Raw and loomstate denim
"Raw" is one of the most stretched words in denim. Iron Heart uses the strictest definition: raw means the same as dry or loomstate, which is fabric that has had no processing at all after it comes off the loom. No singeing, no anti skew treatment and no sanforizing. Its glossary notes that any denim made before 1920 would have been loomstate.
Raw, unsanforized denim is guaranteed to shrink after its first soak, and often a little more over the next few washes. That makes sizing tricky, but fans love it because it keeps more texture and character from the shuttle loom, and because the shrinkage lets the jeans mold closely to your body.
Sanforized and one washed denim
Most denim you buy today is sanforized. Iron Heart explains that sanforization is a pre shrinking process applied after weaving but before the fabric is cut and sewn, patented by Sanford Lockwood Cluett in 1930. The cloth is moistened and passed through a machine that heats the yarns with steam while compacting the weave. That shortens the warp yarns and packs the weft yarns closer together, so the shrinkage happens at the mill instead of in your washing machine.
One washed is a separate step. Iron Heart says that at the final stage of production, most of its finished garments are washed in industrial machines to remove leftover shrinkage and soften the fabric for an easier break in. Iron Heart notes that one washing can be applied to sanforized or unsanforized fabric, which is why labels can be confusing.
The practical takeaway is simple. Sanforized and one washed jeans fit roughly how they fit in the store. Unsanforized raw jeans need to be sized with shrinkage in mind, so read the maker's sizing notes closely.
Rope dyeing and why jeans fade
Most indigo denim is rope dyed. In its glossary, Iron Heart describes the process as twisting yarns into a rope and dipping them again and again into vats of indigo, letting the dye oxidize between dips. Because each dip is brief, the indigo does not fully reach the core of the yarn. The center stays pale.
That pale core is the secret to fading. As you wear the jeans, the surface indigo rubs away and the lighter core shows through. You get whiskers across the lap, honeycombs behind the knees and roping along the hems. The Naked & Famous Weird Guy is a good example: its Japanese selvedge is rope dyed in indigo and, in the brand's words, will slowly fade with wear.
Denim weight in ounces
Denim is measured by weight per square yard of fabric. Iron Heart puts it simply: a yard of 21 ounce denim weighs 21 ounces. Higher numbers mean thicker, stiffer cloth that usually takes longer to break in.
- Lighter weights (around 12 to 14 ounces): comfortable from day one and good for warm climates. The Weird Guy uses 13 ounce selvedge.
- Midweights (around 15 to 17 ounces): a balance of comfort and character. Iron Heart offers a 16 ounce slubby selvedge and a 17 ounce natural indigo selvedge.
- Heavyweights (18 ounces and up): tough, warm and slow to break in. Iron Heart's range runs from 12 ounce up to 25 ounce extra heavy selvedge.
Twill direction and slubs
Denim is a twill, which is why you see diagonal lines across the fabric. The direction of that diagonal is called right hand or left hand twill. The Weird Guy uses a right hand twill, while Iron Heart weaves a 19 ounce left hand twill selvedge. Iron Heart also makes broken twill, where the twill line changes direction to cancel the leg twisting that regular twills can cause.
You may also see "slubby" denim. A slub is a thicker section of yarn that creates small irregularities in the cloth. Iron Heart notes that slubs were first seen as flaws of vintage shuttle looms but are now added on purpose because they give the fabric character.
A real example: the Iron Heart 634S
Iron Heart was founded in 2002 by Shinichi Haraki, who spent 20 years in the Japanese garment industry before starting his own brand for the Japanese motorcycling community. Its 634S is where it all started: a traditional straight cut, medium rise jean in 21 ounce indigo selvedge, and Haraki's first jean design for the brand. The company says the fabric uses a double twisted weft yarn and a lower tension weave, so it is heavy and tough while staying softer and more breathable than other heavyweights.
Caring for selvedge denim
Iron Heart's care guidelines are a sensible place to start. Turn jeans inside out, hand wash or use a short machine cycle with low or no spin, shake out the creases and drip dry. Do not tumble dry, which can cause shrinkage and white marks where the fabric rubs the drum.
How to choose your first pair
Start with the fit you already like, then pick the fabric. If you want an easy start, choose sanforized denim between 12 and 16 ounces. If you want the full shrink to fit experience, look for unsanforized or loomstate cloth and follow the maker's sizing advice. Either way, wear them often. Selvedge denim is at its best when it carries the story of the person who wears it.
Keep reading: our look at the Naked & Famous Weird Guy, our raw denim beginners guide, our guide to Japanese denim brands and our explainer on Momotaro Jeans. For more, visit our sneakers and style hub.
