There is a lot of talk going on about selvage and it’s generally accepted that the old school way of weaving creates higher quality fabrics. However, selvage denim isn’t necessarily more durable than non-selvage denim, which is a common misinterpretation. The real difference between the two weaving methods is how the denim fades, which then again also depends on the yarn that is used. One of the most significant steps in the production process of turning raw cotton into denim is the spinning of the yarn, which is be crucially important to how the denim will eventual turn out with wear.
As selvage denim is much more time and cotton consuming to produce compared to weft inserted projectile loom denim it makes sense to use high quality yarn for it – just like you would prefer a V8 in your muscle car. There are two predominant commercial systems of yarn spinning, ring spinning and open end spinning. Ring spinning yarn was generally used in denim production until the late 70s, but as the cheaper and less cotton consuming open end spinning was introduced it quickly became the standard of the industry. But with the growing demand for vintage denim ring spinning is gaining grounds again.
The ring spinning machine was invented in America in 1828. It has undergone considerable modification since then, but the basic concept remains the same. However, the productivity of the ring spinning machine has increased by 40% since the late 70s. Especially with short staple spinning, the ring spinning machine has considerable advantages over the new spinning processes.
The manufacturing process from raw material to spun yarn takes the cotton through a number of step including preparation, carding, combing, drawing, twisting and finally spinning. As ring spinning accounts for 60% of the spinning mills total costs it’s self-evident that this is where development has been focused.
Preparing the fibres means unpacking, cleaning and blending. After that the fibres are separated and pulled into a roughly parallel form by the carding machine. The fibres are then further parallelled by combing. After carding and combing the fibre mass is referred to as the sliver. Combining several slivers beforehand, a series of rollers rotating at different speeds elongate the sliver into a single uniform strand that is given a small amount of twist and fed into large cans. The final step before spinning is twisting.
In ring spinning, the sliver is fed through a machine called the roving frame where the strands of fibers are further elongated and twisted. The roving is fed from the spool through what is known as rollers. These rollers elongate the roving, which passes through the eyelet, moving down. The spinning happens as a traveler moves freely around a stationary ring. Watch how it happens here.
Open-end spinning omits the roving step. Instead, the sliver is fed into the spinner by a stream of air. The sliver is delivered to a rotary beater that separates the fibres into a thin stream that is carried into the rotor by a current of air through a tube or duct and is deposited in a V-shaped groove along the sides of the rotor. As the rotor turns, the twist is produced.
With denim the difference between the two spinning methods becomes evident with numerous wears and washes. One of the main characteristics of ring spun yarn is its slubbyness and uneven surface, which is a result of its varying diameters. This gives the fabric an authentic vintage look once worn and washed. Additionally, ring spun yarn is both softer and more durable compared to open end yarn. Slubs can also be imitated on open end yarns.
As the fibres in open end yarn are generally not spun in a parallel direction open end denim is more fuzzy compared to ring spun yarn (see drawing above). As a result, the yarn absorbs more indigo deeper into its core which will eventually make it harder for you to get those highly contracted fadings. And there you have it. So what’s the conclusion of all this highly technical nonsense? Well, next time you go out hunting for a pair of selvage denim jeans make sure you ask if they’re made of ring spun yarn.