A little Denim know-how

Selvedge, Nep, Slub, Low Tension & Kibata

If you're into denim, specially Japanese denim, you've probably come across words like selvedge, nep, slub and kibata. Or heard someone talking about low-tension weaving.
They're often used when talking about Japanese denim, but what do they actually mean? And why do they matter?
Here's a little denim know-how for the curious.

Selvedge: It's all about the edge (and the loom)

Selvedge refers to the self-finished edge of a fabric. In traditional selvedge denim, this edge is created on a shuttle loom, which weaves a continuous weft thread back and forth across the fabric.
These looms produce narrower fabrics and generally work more slowly than modern industrial looms. Depending on the yarns, weaving tension and finishing methods, they can produce fabrics with distinctive textures and character.

So why is selvedge denim so valued?
Partly for the weaving tradition, the slower production process and the variety of fabrics that can be created using these machines.
That little coloured line you see when you turn up your jeans? That's the selvedge edge.
But selvedge doesn't automatically mean better quality. The cotton, yarn, construction and finishing all play an important part.

Nep: Those little cotton specks

Nep, or neppy, refers to tiny knots or clusters of cotton fibres in the yarn. They appear as little specks across the fabric, often white against the indigo. These irregularities create a grainy, slightly rough appearance that gives the denim a lot of visual texture. Depending on the fabric and how it's worn, the neps can become more noticeable as the indigo fades.

Slub: Beautifully uneven yarn

Slub refers to irregularities in the thickness of the yarn. Thicker and thinner sections create an uneven texture, often with visible vertical streaks running through the fabric.
Slubby yarns can be deliberately produced to create this effect, giving the denim a more irregular surface.
As the fabric ages and fades, these variations can become even more pronounced.

Low Tension: A more relaxed weave

Low-tension denim is woven with relatively low tension on the yarns, allowing for a more relaxed fabric structure. Rather than producing a perfectly uniform surface, this approach can create subtle variations in texture, giving the denim a slightly uneven appearance.
As the denim softens and fades with wear, these variations can become more visible, adding to its character over time.
Low-tension weaving is often associated with traditional Japanese denim production, where weavers experiment with yarns, loom settings and weaving techniques to create fabrics with distinctive qualities. And low tension doesn't necessarily mean lightweight denim.
Even heavyweight fabrics can be woven with relatively low tension.

Kibata: Straight off the loom

Kibata is the Japanese term for fabric in its loomstate — straight off the loom, without washing, pre-shrinking or finishing treatments. Unlike sanforized denim, which has been mechanically treated to reduce shrinkage, kibata retains its original, untreated structure.
This means it can shrink considerably during its first wash, as the yarns relax and the fabric settles. It also means the fabric keeps much of its original texture and character.

For people who enjoy watching denim evolve, this is part of the appeal. The fabric starts changing from its very first wash and continues to develop with wear.

It's all about the process

From yarns and weaving to finishing, every detail shapes how denim looks, feels and ages. And yes, a single fabric can combine some or even all of these characteristics.
That's what makes denim so interesting to us. Two fabrics can look similar when they're new, but develop completely differently over time. And that's part of the beauty of it.

The story doesn't end when the fabric leaves the loom. In many ways, it's just getting started.