Selvedge denim is generally heavier weight, and the looms can only cope with a certain width of cloth, they were disposed of when denim got really popular, and the manufacturers needed to get more material usage out of a given width of cloth, the old looms can do enough for one pair across the width, which is why it tends to be more expensive, and it’s more labour intensive. Selvedge denim is more often dyed using natural indigo dye, whereas mass-produced denim uses chemical dye. Indigo denim has a very distinct odour, slightly musty, and it fades better as well.
Selvedge on a pair of jeans
Selvedge denim (alternative spelling: selvage denim) is a type of denim which forms a clean natural edge that does not unravel.[citation needed] It is commonly presented in the unwashed or raw state. Typically, the selvedge edges will be located along the out-seam of the trousers, making it visible when cuffs are worn.[citation needed]
The word “selvedge” comes from the phrase “self-edge”, the natural edge of a roll of fabric.[citation needed] As applied to denim, it means that which is made on old-style shuttle looms. These looms weave fabric with one continuous cross thread (the weft) that is passed back and forth all the way down the length of the bolt. As the weft loops back into the edge of the denim it creates this “self-edge” or selvedge. Selvedge is desirable because the edge cannot fray like denim made on a projectile loom that has separate wefts, which leave an open edge that must be stitched.[citation needed] This advantage is only realized on one edge of the fabric, however, as the fabric has to be cut to shape and anywhere it is cut the self-edge is lost.
Shuttle looms weave a narrower piece of fabric, and thus a longer piece of fabric is required to make a pair of jeans (approximately 3 yards).[citation needed] To maximize yield, traditional jean makers use the fabric all the way to the selvedge edge.[citation needed] When the cuff is turned up, the two selvedge edges (where the denim is sewn together) can be seen. The selvedge edge is usually woven with a coloured stripe: green, white, brown, yellow, and (most commonly) red.[citation needed] Fabric mills used these colours to differentiate between fabrics.[citation needed] Contrary to popular belief, the stripe is not sewn in finishing the product, but woven into the fabric itself.[citation needed]
Most selvedge jeans today are dyed with synthetic indigo, but natural indigo dye is available in some denim labels.[citation needed] Though they are supposed to have the same chemical make-up, there are more impurities in the natural indigo dye.[citation needed] Loop dying machines feed a rope of cotton yarn through vats of indigo dye and then back out. The dye is allowed to oxidize before the next dip. Multiple dips create a dark indigo blue.[citation needed]
In response to increased demand for jeans in the 1950s, American denim manufacturers replaced the old shuttle style looms with modern projectile looms. The new looms produced fabric faster and wider (60 inches or wider).[citation needed] Synthetic dying techniques along with post-dye treatments were introduced to control shrink and twist.[citation needed]