DU 103: Sanforized vs. Shrink to Fit

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By Eric Steffen
Founder / Maker
FITTED Underground

Before buying your first pair of raw denim jeans, there's a simple question that should be answered at the start — has this denim been pre-shrunk? If yes, buy snug. If no, bump up two sizes and two inches at the inseam. At least, that's the rule of thumb.

But what about all those terms? Loomstate, kibata, STF, sanforized — and do I need to bathe with my jeans on!? This article explains the difference between pre-shrunk and, well, not pre-shrunk denim — and all the confusing definitions along the way. Let's dive in.

All Raw Denim Starts the Same Way

Before we get into the difference between shrink to fit (which we'll call unsanforized) and pre-shrunk (which we'll call sanforized), it's worth quickly noting: both are raw denim. They are siblings on the same family tree, not different species.

Every piece of denim begins life as a loomstate fabric. Fresh off the shuttle loom, the fabric exists in its most unprocessed state: slightly stiff, carrying residual starch from the weaving process, and covered with fine surface hairs called griège (pronounced "grehj" — a French textile term for raw, unfinished fiber). These surface hairs are a natural characteristic of cotton yarn that hasn't been processed — they give loomstate denim its distinctive hairiness and contribute to the fabric's texture and character. The loomstate of denim is also known as shrink to fit (STF), unsanforized, and the Japanese term, kibata. Lots of terms — that mean the same exact thing.

Sanforization — the process of pre-shrinking denim — is something that can happen to the fabric afterward. The vast majority of denim is pre-shrunk: globally, perhaps 99% of all denim, and even within the raw denim world, something close to 95%. The people have spoken, and most want shrinkage out before making the purchase. Sanforization uses steam, mechanical stretching, and heat to expand and then shrink the fabric, removing the shrinkage that would otherwise occur after the first wash. The upshot: whereas unsanforized denim will shrink 7–10%, sanforized denim will shrink only 1–3%. A significant difference.

Both sanforized and unsanforized are raw denim.
The difference is what happens immediately after the loom.

The Sanforization Machine — A Brief History

Before 1930, every pair of jeans in the world was shrink-to-fit. This wasn't a niche preference — it was simply how denim worked. Buyers bought large, washed down, and hoped for the best. Levi's famously sold its jeans with a "shrink-to-fit" label not as a feature but as an honest description of what was going to happen whether you wanted it to or not.

The man who changed that was Sanford Lockwood Cluett — an American inventor and engineer who had spent his early career, colorfully enough, wrestling alligators in Florida and serving in the engineer corps during the Spanish-American War. In 1930 he patented a mechanical process for pre-shrinking woven fabric before it was cut and sewn into garments. The sanforization machine was born, and within a generation it became standard in the global textile industry.

The machine itself is remarkable. Rolls of loomstate fabric are fed continuously through a series of heated rollers and treatment chambers. The process begins with steam — hot, pressurized steam applied directly to the fabric to relax and open the cotton fibers, making them receptive to controlled shrinkage. In many mills, the fabric also passes briefly through open flame at this stage, which singes off the griège — those fine surface hairs — cleanly and quickly. This is not a violent process but a precise one: the flame is calibrated to remove the surface hairs without damaging the underlying yarn. The result is a smoother, more uniform fabric surface.

After the steam and singeing, the fabric is compressed and stretched in a carefully controlled sequence until the fibers have been mechanically pre-shrunk to their post-wash dimensions. What would have happened unpredictably in your washing machine has now happened under controlled conditions at the mill. The finished fabric will shrink only about 1 to 3 percent after purchase — a predictable, manageable amount — rather than the 7 to 10 percent you'd get from unsanforized denim on its first encounter with water.

The trade-off is real, if subtle. The steam and flame process takes something from the fabric. The surface hairs that sanforization singes away are part of what gives loomstate denim its texture and hand. The mechanical compression smooths the fabric slightly, reducing some of the irregularity that shuttle loom weaving produces. To most wearers these differences are imperceptible, especially when new. To an advanced denim enthusiast who has handled both, the distinction is small but meaningful — like the difference between a wine that has been filtered and one that hasn't. Both are good. One has had something subtle removed in the interest of consistency.

For most people, the trade-off makes complete sense. A pair of jeans that fits predictably and still develops beautiful fades over years of wear is the right answer for the overwhelming majority of raw denim buyers.

Sanforization is like filtering a wine. Both versions are good.
One has had something subtle removed — and for most people,
that trade-off makes complete sense.

Unsanforized — What You Get and What You Give Up

Unsanforized denim has never been through the sanforization machine. It arrives exactly as the loom produced it: surface hairs intact, every irregularity in the weave preserved, the full character of the fabric uncompromised.

The trade-off is shrinkage — significant, somewhat unpredictable, and entirely your responsibility to manage. Typically 7 to 10 percent on first contact with water, which can translate to one to two full sizes in the waist and two or more inches in the inseam. This is why sizing up is essential, and why the inseam needs to be cut long before the first soak.

For the first-time raw denim buyer, this variability is the main reason to avoid unsanforized. Not because the fabric is inferior — it isn't — but because the fit management adds a layer of complexity that distracts from what should be the main event: learning to love raw denim. Getting the fit wrong on your first pair because you mismanaged the shrinkage is a frustrating way to start.

For the experienced denim enthusiast, unsanforized is often the preference precisely because of what it preserves. The griège — those surface hairs that sanforization removes — creates a more complex, more interesting fabric surface that develops fades with slightly more character and texture. The fabric feels different in the hands, different against the body, and behaves differently over years of wear. Some of the most beautiful denim in the world is kibata.

Some of the most beautiful denim in the world is "kibata". 
The griège, the texture, the depth — it's denim in its purest form. 

The most devoted enthusiasts take the experience one step further: soaking the jeans while wearing them, standing in a bathtub of lukewarm water and letting the fabric contract and conform to the precise geometry of their body as it shrinks. The result is a fit that no size chart can produce — shaped specifically to you, to your body, to the way you stand and move. It is time-consuming, slightly absurd, and genuinely extraordinary. Even after a decade of making jeans at FITTED Underground, it's still on my personal to-do list. Some experiences take time to earn.

The One-Wash Middle Path

Between fully sanforized and fully unsanforized there is a third option that doesn't get enough attention: one-wash denim, sometimes called pre-soaked or rinsed denim.

The concept is straightforward. Unsanforized kibata fabric is given a single controlled rinse — either before the garment is cut and sewn, or after — to remove most of the initial shrinkage without going through the sanforization process. No steam rollers, no open flame, no mechanical compression. The surface hairs remain largely intact. The texture and character of the loomstate fabric are preserved to a much greater degree than sanforization allows. But the unpredictable 10 percent shrinkage has been removed, replaced by a stable, manageable fabric that sizes predictably.

At FITTED Underground we recently produced a run of jeans called the D13 Teal Kibata — an unsanforized Japanese selvedge fabric (kibata, by name and by nature) that we pre-soaked and gave a light tumble dry with dryer balls to soften and stabilize before finishing. The results were exceptional. The fabric retained its full loom character — the texture, the surface interest, the depth that kibata carries — while fitting predictably and wearing beautifully from the first time they were put on. It's the best of both worlds, and it's the approach I'd recommend to any intermediate denim buyer who wants to explore unsanforized fabric without the sizing guesswork.

One honest note: one-wash garments take more time and care to produce than their sanforized equivalents. The pre-soak process adds a production step. They will typically cost a little more as a result. In this case, the premium is earned.

A Simple Guide to Choosing

First-time raw denim buyer: Choose sanforized. Buy snug — expect the top block to expand by roughly one size as the fabric relaxes with wear. Enjoy the ride without worrying about shrinkage.

Experienced enthusiast who wants more loom character: Consider one-wash kibata. You get the texture and depth of unsanforized fabric with predictable sizing. The best of both worlds.

Advanced denim devotee who wants the full experience: Unsanforized is for you. Size up two full sizes and add at least two inches to your inseam. Then soak them, either on or off your body, and let the fabric finish drying on you. We've heard great stories of clients showering in their shrink-to-fit denim or jumping in a tub or the ocean. However you get them wet is up to you — but the critical aspect is to allow them to air dry on your body. This allows the fibers to mold to your contours and offer you a truly remarkable fit.

What Comes Next

Now that we've done a deeper dive into the two forms of raw denim — and how to choose between them — the next foundational question is: how heavy do you want to go? From featherlight 7oz summer fabric to armor-plated 21oz denim, the weight affects how a pair of jeans feels, wears, and fades. That's DU 104: Denim Weight Explained.

← Previous: DU 102 — What is Selvedge Denim?  |  Next: DU 104 — Denim Weight Explained →

Further Reading

• Sanforized vs. Unsanforized Raw Denim — Heddels
• Sanforized vs. Unsanforized vs. Raw — Stridewise
• Sanforized vs. Unsanforized — Okayama Denim
• The Guide to Sanforized, Unsanforized, and One-Washed Denim — Rivet & Hide

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.