Discover How Denim Is Woven and Learn About the 3 Key Inventions That Have Revolutionised Weaving
The main reason that knowledge about how denim is woven has become household trivia is the popularity of selvedge denim. Ever since the connoisseurs that started the vintage denim scene began identifying jeans as valuable based on the edges of shuttle-loomed denim, weaving has been something denimheads talk about.
But why do we have two different methods for weaving denim? How did weaving evolve? Actually, what is weaving? That’s what this article answers.
The five production stages of denim that the series discusses:
What Is Weaving?
Weaving is defined as the interlacing of two sets of yarn at a fixed 90° angle. It’s the yarns’ right angle at one another that distinguishes weaving from knitting in which the yarn meanders in a series of interlocking loops.
The two sets of yarn in a weave perform different tasks. The yarns that run across—known as the weft, the filling or the pick—is threaded over and under the yarn that runs downwards, which is called the warp or ends.
To weave a piece of fabric, you need three principal motions: shedding, picking and battening. First, shedding moves the warp yarn up and down to create the weave pattern. Next, picking interlaces the weft with the warp. Finally, battening presses the weft in place after the interlacing.
For denim, the dye is important too. Denim is woven from an indigo-dyed cotton warp yarn and an undyed (or bleached) weft yarn. However, with the advancement of alternative dyes such as sulfur, I would argue that the definition of denim can be stretched to include garment-dyed twills as well.
Regarding the type of weave, denim has traditionally been woven as a 3×1 right hand twill. “3×1” tells you that, on the fabric’s face (i.e. its front), you have three warp yarns for every weft yarn. “Right hand” tells you that the diagonal twill line runs from right to left on the face of the fabric.
Fabric designer, Stefano Aldighieri of Another Design Studio, adds that a handful of twill weave variations are also defined as denim. There’s the 2×1 twill, where you have two warp yarns for every weft yarn. And both 3×1 and 2×1 can also be left hand twill, meaning the diagonal twill lines runs from left to right. There’s also broken twill, which was invented to prevent the fabric from pulling in the direction of the weave, which results in ‘leg twist.’ And a 1×1 plain weave chambray is in fact also a denim; he points out.
That’s the “what” of weaving. But how did weaving evolve into what it is today?
The Groundbreaking Invention That Changed Weaving
We humans have been weaving fabrics for thousands of years. The device used to weave is called a ‘loom.’ The earliest looms were made in the New Stone Age, more than 12,000 years ago. Of course, back then, looms were operated by hand.
One type of ancient hand-operated loom is the warp-weighted loom, which consists of a frame that is made from poles that are placed in a vertical position. The warp yarn is kept taut by weights, which allows the weaver to thread the weft.
Another ancient loom is the backstrap loom. The weave is made up of two rods that have yarn stretched onto them. The rod at the top is fixed to somewhere high while the bottom rod is fixed to the back of the weaver with a strap.
The more direct ancestors of the machines that weave our denim today are the treadle loom and the drawloom. These looms mechanised the shedding, which was a groundbreaking invention.
Shedding is done with the ‘heddle’—sometimes also referred to as the ‘heald frame’ or the ‘harness’. A series of bars that extend the width of the loom are suspended on a shaft. On each bar is a number of ‘heddles’; wire or cord with an eyelet in the middle for the yarn to pass through (as seen above).
The bars can move up and down; traditionally, they were activated by a footswitch called the ‘treadle.’ When the weaver would activate a treadle, one bar would be raised while the other would remain below. The result is an intricate mesh that the weft can pass through. And that space is called the ‘shed.’
With the shed, the weaver could easily thread the weft. The weft was held in a ‘shuttle,’ a bullet-shaped tool with a bobbin filled with the weft, which would be thrown through the shed. Once caught on the other side, the weft would be secured with a bar called the ‘beater’ in the battening motion.
The heddle and the beater are still part of even the most advanced weaving machines of today—although they’ve obviously been automated. What’s changed most is the picking.
Automating Weaving with 3 Inventions in Picking
The automation of weaving began during the early Industrial Revolution. Shedding and battening were relatively easy first to mechanise and later automate; today, we don’t talk much about these two motions of weaving.
It’s the evolution of the picking process that gets the most attention. That’s because the speed of the picking hugely determines the capacity of the weave. In other words, it’s the picking that creates bottlenecks.
There are three key inventions in weaving’s automation that have happened in the picking process:
- The flying shuttle
- Filling-changing battery
- Shuttleless picking
The Flying Shuttle
The first revolutionising invention in picking dates back to 1733 when John Kay presented the flying shuttle. Before the flying shuttle, a single weaver could only weave at arm’s length. For wider fabrics, operators had to throw and catch the shuttle, which was a two-man job.
In Kay’s invention, the shuttle is propelled back and forth through the shed as the weaver flicks what’s known as the ‘picking stick’ left and right with his wrist. Doing so pulls a cord that is attached to the shuttle.
Towards the end of the 1700s, the first power-driven looms appeared. Edmund Cartwright’s power loom of 1784 was the first, but it wasn’t economically feasible. Many inventors worked on improving the design, but power looms didn’t become viable alternatives to handlooms until Kenworthy and Bullough’s semi-automatic Lancashire loom was introduced in 1841.
The Lancashire loom notified the operator if a warp yarn broke. And when the shuttle ran out of weft yarn, the machine stopped. This meant that one operator could work four or more looms at the same time; previously, they could only work a single loom.
Still, it wasn’t until 1894 that the first fully automatic loom was introduced.
The Filling-Changing Battery Made Looms Fully Automatic
Most denimheads recognise the company that made the first automatic loom: Draper Corporation. It was a ‘filling-changing battery’—developed by one of the companies loom mechanics, John Henry Northrop—that made complete automation achievable.
Northrop’s battery closely resembles a Gatling gun; only it’s loaded with shuttles instead of bullets. When it’s detected that a shuttle is empty, the loom is automatically reloaded with a fresh one. All without stopping the loom.
Named the A-model—but often referred to as ‘the Northrop’—it became a massive success. By 1914, Northrops made up 40% of looms in American mills. Over the years, no less than 700,000 ‘Northrop’ shuttle looms were sold, which established Draper as the leading American loom maker. The Northrop was best suited for coarse yarn, just like the kind used in denim.
Draper isn’t the only maker of automatic shuttle looms that’s been used to weave denim—you also have the likes of Picanol from Belgium and Toyoda from Japan. But Draper is probably the most recognised. That’s mainly because Cone Mills’ White Oak plant still relies on restored Draper looms to make selvedge denim.
These days, shuttle-loomed denim is loved for its aesthetics. As Stefano Aldighieri explains, weaving on a shuttle loom is slow compared to modern day standards. That means less tension on the yarn, which makes the denim fade more beautifully. Shuttle looms also tolerate more slubs in the yarn, which give character to the denim.
However, back in the day, denim makers wanted faster weaving and more consistency. And that’s what the third key invention in picking offered.
From a capacity standpoint, the problem with the shuttle is its size. It takes force and time to propel a 40-centimetre piece of wood with a spool of yarn back and forth. The solution was to go shuttleless and thread only one weft yarn at a time.
The world’s first shuttleless loom was built in 1930, following three years of research, by the German textile engineer, Rudolf Rossmann. In 1933, the Sulzer company of Switzerland invested in the project. At the height of the WWII, in 1942, the Swiss company secured the exclusive rights to the shuttleless technology.
Sulzer’s shuttleless loom replaced the shuttle with a small metal device that resembles a bullet in appearance. That’s why it’s commonly known as a ‘projectile loom.’
As the projectile grips onto the end of the weft yarn, it’s shot across the shed carrying the weft with it. At the other side, another projectile is fired back across the shed with a new weft pick. Because the weft yarn is cut off with each pick and not looped back and forth in a shuttle, the edges of the fabric are frayed and unfinished.
In the 1940s through the 1960s—the time when the foundation for shuttleless loomed-denim was laid—it didn’t matter much to anyone if a pair of jeans had selvedge edges or not. What mattered was that the speed of weaving on shuttleless looms was increased from 140–160 to 400–600 picks per minute. At the same time, the weaving frame could be widened, which further increased production capacity.
Eventually, Draper also got into the shuttleless loom business. After the American loom maker had turned down Sulzer’s offer to the US rights to their projectile technology, it developed a loom that relies on finger-like carriers known as ‘rapiers’ to shoot the weft yarn across the shed. This technology didn’t require Draper to change the production setup to aluminum from iron, which was what they shuttle looms were built from.
The first shuttleless Draper loom, the DSL, was launched in 1959. The following year, Sulzer began exporting Swiss-made projectile looms to the US. In the end, Sulzer’s technology proved superior, and that became the end of Draper.
Want more stories like this one?
The next episode of my ‘how denim is made’ series discusses fabric finishes. You can read it here.
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