DU 306: How to Repair Raw Denim — Darning, Patching, Sashiko and Boro

By Eric Steffen
Founder / Maker
FITTED Underground

Here is where things get exciting.

The first six months of wearing a pair of raw denim jeans are about establishing fades and building the foundation. The next year is about deepening them. And then, eventually — for anyone who wears their jeans the way jeans were designed to be worn — comes the moment when the fabric at the crotch begins to thin, or a small hole appears at the knee, or the pocket corner starts to fray. This is not a failure. This is a milestone. It is proof that you have worn your jeans hard enough and long enough that the fabric has given something back — a record of wear that no factory process can replicate, and a garment that is now genuinely worth repairing.

Repair is where raw denim culture gets philosophical. The fast fashion world's answer to a worn garment is disposal. The raw denim world's answer is the opposite: invest more in it. A well-executed repair does not diminish a pair of jeans — it adds to them. It extends the story. It adds another layer of human intention to an object that has already absorbed years of a specific life. And in the hands of someone who knows what they're doing, a repair can be more beautiful than the original construction.

This article covers the full spectrum of repair techniques — from the quick patch to the meditative practice of boro — and explains when and why to use each one.

One note before we begin: sashiko and boro are repair techniques with deep roots in Japanese textile history. For the full story of those origins — the Edo-period farmhouses of northern Japan, the hikeshi firefighters, the philosophy of mottainai — read DU 705: Sashiko Fabric Explained. This article focuses on the repair applications. DU 705 covers the history and the material.

The Repair Spectrum

Denim repairs exist on a spectrum from utilitarian to artistic. At one end, a patch applied in ten minutes that stops a hole from growing. At the other, a boro garment that has accumulated decades of accumulated human intention in fabric and thread. Between those poles is a range of techniques — darning, color-matched thread work, sashiko stitching — that offer different balances of speed, invisibility, durability, and beauty.

The right repair depends on three things: the size and location of the damage, how visible you want the repair to be, and how much time and skill you want to invest. All of these are legitimate variables and there are no wrong answers. A quick patch on the interior of a crotch blowout is not inferior to a sashiko-stitched exterior repair — they are solving the same problem with different priorities.

One universal principle: repair earlier rather than later. A thinning area caught before it actually tears can often be darned invisibly, with no backing fabric required. A full blowout requires backing fabric, more thread, and more visible intervention. The fabric will always tell you it's thinning before it fails — a slight translucency, a softening of the weave, a change in how the fabric feels under your fingers. That is the moment to act.

Technique One: Darning

Darning is the foundation of all denim repair. It is the process of rebuilding damaged fabric by sewing over it — running thread back and forth across a hole or thinning area until a new layer of material has been created, woven from thread rather than yarn but functionally replacing what the original weave has lost.

The basic process: position the damaged area flat and taut. If the hole is significant — more than a small tear — place a piece of backing fabric behind it first, on the interior of the garment, to give the darning thread something to anchor to and to prevent the repair from puckering. The backing fabric should match the color of the jeans as closely as possible; this is where access to original fabric from your maker makes a real difference.

Then choose your thread. This is where darning raw denim becomes genuinely interesting.

A pair of well-worn raw denim jeans is not a single color. It is a map of colors — deep indigo in the protected low-friction zones, near-white at the high-friction points, and every gradation of blue between. The damaged areas, typically at the crotch and knee where friction is highest, will have their own specific color profile. Matching that profile is the work of a painter more than a tailor.

Start with a darker thread to match the deepest indigo tones in the repair area. Work the darning stitches in the direction of the warp — vertically on the garment, following the direction of the original weave. For larger areas with significant color variation, you will return to specific zones with lighter thread, working over the areas that correspond to the whiter, more faded portions of the surrounding fabric. The goal is blending — a repair that, from a normal viewing distance, reads as part of the fabric rather than on top of it.

Thread weight matters. A heavier thread builds up fast and creates a thick, stiff repair that you'll feel with every step. A lighter thread — a tex 21 or similar — takes more passes to cover the area but produces a result that is much closer to the hand of the original fabric. There are extensive color ranges available in lighter thread weights, which makes color matching achievable even on complex fade profiles. When in doubt, go lighter.

The darning stitch typically follows the warp of the jean. For very large repairs, you may occasionally stitch across the weft first to create a grid foundation — but this is the exception rather than the rule. The grain of the fabric is your guide.

[Photo: darning repair example — TBD]

Technique Two: The Patch

A patch is the most direct repair. A piece of fabric — denim, canvas, or any other sturdy material — is applied over or behind the damaged area to reinforce it and stop the damage from spreading. No color matching required. No specialist equipment. Fast, effective, and honest.

Two approaches: interior or exterior.

An interior patch is hidden inside the garment. It reinforces the damaged area from behind without changing the visible surface of the jeans. This is the right approach when you want the repair to disappear — when the priority is function over aesthetics and you'd prefer that the fix not announce itself. The patch is stitched to the interior fabric, the damaged area on the exterior is left as-is or lightly darned to prevent further fraying, and from the outside the repair is invisible or nearly so.

An exterior patch sits on the outside of the garment. It is visible by design — a deliberate statement rather than a hidden fix. The patch fabric can match the original denim (for a tonal result) or contrast it (for a graphic, intentional look). Exterior patches are faster to apply than interior ones in some configurations, and they have a long tradition in workwear and military clothing — the original function of the patch was never concealment but reinforcement, and there is nothing wrong with wearing that honestly.

The choice between interior and exterior, matching and contrasting, is entirely a matter of what you're trying to achieve. There is no hierarchy. A contrasting exterior patch on a pair of heavily faded jeans can be striking. An invisible interior patch on a pair you want to keep looking unworn is equally valid.

[Photo: patch repair example — TBD]

Technique Three: Sashiko Repair

Sashiko takes the patch and transforms it into something else entirely.

In its repair application, sashiko involves applying a reinforcing piece of fabric — typically indigo-dyed cotton — over or behind a damaged area, then stitching it to the garment using the traditional sashiko running stitch: dense, repetitive, geometric, worked in thick white thread. The result is a repair that is unmistakably visible, deeply intentional, and genuinely beautiful.

The white thread against indigo fabric — especially indigo that has been fading for years — creates a visual contrast that is the opposite of the darned repair's invisibility. Where darning tries to disappear, sashiko announces itself. The geometric patterns — waves, diamonds, interlocking circles, grids — are worked deliberately across the surface of the patch, covering it completely and extending slightly beyond its edges into the surrounding fabric to distribute the structural reinforcement over a wider area.

This is also where the color dynamic of a well-worn pair of jeans becomes particularly interesting. Sashiko stitched in white thread over deep indigo fabric creates one contrast. The same stitch worked over an area that has faded toward pale blue or near-white creates a different contrast — quieter, more integrated. The repair reads differently depending on where it lands in the fade map of your specific pair of jeans. No two sashiko repairs look exactly alike, because no two pairs of jeans fade exactly alike.

The technique is meditative. It requires patience — particularly for larger repairs over the crotch or knee where the stitch area is substantial. But the work accumulates in a way that is satisfying in a way that most repair work is not. Each pass of the needle adds to something visible and growing. The repair becomes a collaboration between the wearer's years of wear and the repairer's hours of stitching.

For the full history of sashiko — its origins in Edo-period Japan, its use by firefighters and martial artists, its preservation in Tohoku, and its contemporary revival — read DU 705: Sashiko Fabric Explained.

[Photo: sashiko repair example — TBD]

Technique Four: Boro

Boro (ぼろ) — the word means "rags" or "tattered cloth" in Japanese — is what happens when repair becomes a practice rather than an event. It is not a single technique but a philosophy: the accumulation of patches and stitching over time, building up layers of repair that eventually transform the original garment into something new.

It emerged in rural Japan during the Edo period (1603–1868), particularly in the northern Tohoku region, where winters were brutal and cotton was a luxury that had to be imported from the warmer south. Fabric was precious in a way that is difficult for the modern consumer to imagine — not precious in the way that a luxury good is precious, but precious in the way that survival depends on it. You did not discard a worn garment. You repaired it. And when the repair wore through, you repaired the repair. And when the patch frayed, you patched the patch. Generations of hands added their stitching to the same piece of cloth, until the original garment was almost unrecognizable beneath the accumulated layers of human intention.

The philosophy behind boro is mottainai (もったいない) — a Japanese concept that translates roughly as "what a waste" or "too good to waste." It is the feeling of regret at squandering something that still has value. In a world where fast fashion has made disposability the default, mottainai is a counter-argument with centuries of precedent behind it.

In the twentieth century, boro was considered shameful — the clothing of poverty, worn by people who could not afford better. Families who had worn boro garments out of necessity discarded them as soon as factory-made cloth became affordable, eager to leave hardship behind. It took collectors and textile scholars to recognize what was being lost. Today, historic boro textiles are held in museum collections in Tokyo, New York, and across Europe, recognized as extraordinary examples of both textile art and human resilience.

In the raw denim world, boro has been embraced as the ultimate expression of the repair philosophy. A pair of jeans that has been worn, patched, stitched, re-patched, and re-stitched over years is the living embodiment of everything the slow fashion argument is about. The garment doesn't end when it wears out. It continues — in a different form, with a different surface, but carrying all of the previous wear and all of the subsequent repair as a layered record of the life it has been part of.

A single patch can look crude. A collection of patches, worked in sashiko, accumulated over years of wear and repair, is something else. As the fabric fades around the patches — as the original indigo lightens while the newer patch fabric starts darker — the visual complexity deepens. The garment becomes topographical. You can read its history in the layers.

This is the endpoint of the repair spectrum. Not every pair of jeans will get there. But every pair of jeans that has been genuinely worn and cared for is on the path toward it.

[Photo: boro repair example — TBD]

When to Repair and When to Bring It In

Many of the repairs described in this article can be done at home with basic equipment — a needle, the right thread, some patience. Darning in particular requires nothing more than steady hands and good color judgment. Patch application is straightforward. Basic sashiko stitching is accessible to anyone willing to learn the running stitch.

But there are situations where professional repair produces meaningfully better results:

Large crotch blowouts where the damage extends across the inseam seam itself, not just the fabric panel. Repairing into and across a seam requires understanding how the original seam was constructed and how to restore its structural integrity — not just cosmetically but mechanically.

Knee repairs that require sewing through a cylinder — the finished leg — which needs the right machine and the knowledge to use it. The same specialty operation described in DU 305 for leg tapering applies here.

Complex color-matching on highly faded jeans where the repair area spans multiple tonal zones and the darning work requires experience with thread blending across a complex surface.

Sashiko repairs on significant areas where the stitching needs to be consistent and geometrically precise over a large surface. This is learnable, but it takes practice to execute well on a first attempt.

FITTED Underground does repair work on our own jeans and on jeans from other makers. For details on our repair services, visit our alteration and repair services page.

The Repair as a Statement

There is a version of clothing culture that treats a worn garment as a failed garment — something that has reached the end of its useful life and should be replaced. The raw denim world has always operated on a different premise: the garment is not failing, it is maturing. The wear is not damage, it is character. And the repair is not a remedy for failure but a continuation of something worth continuing.

Boro textiles that are now held in museum collections were not made by artists. They were made by farmers and fishermen who couldn't afford to throw anything away. What makes those objects extraordinary is not that they were made to be art — it's that they were made to last, by people who understood that the things you own are worth taking care of. That understanding is available to anyone who owns a pair of raw denim jeans and is willing to repair them rather than replace them.

Wear them. Repair them. Keep living your best life. Your jeans will be living theirs.

What Comes Next

DU 306 closes the 300 level — the care and wear section of the curriculum. The 400 level goes deeper into the craft itself: how denim is actually made, how a pattern is drafted, what happens in a workshop like ours. Coming soon.

← Previous: DU 305 — How to Alter Raw Denim  |  Denim University Hub →

Further Reading

• How Jeans Can Be Repaired — and When They Can't — Permanent Style
• Mended Histories: The Emergence of Japanese Boro Textiles — Retrospect Journal
• How Boro Became Art — Carryology
• 6 Denim Repair Shops to Send Your Jeans To — Heddels

Eric Steffen is the founder of FITTED Underground, a custom jeans and raw denim workshop at 108 Bayard Street in Williamsburg, Brooklyn. He has been making jeans by hand since 2014. Denim University is his attempt to share everything he's learned — about the history, the craft, and the culture behind the world's most enduring garment.