Sanforized and unsanforized denim

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This Encyclopedia entry is a must-know term. Learn more in our Denim vocabulary.

Sanforization is a process of pre-shrinking fabric before it is made into a garment.

When a fabric has been treated with the sanforization process, it’s referred to as ‘sanforized’ or ‘pre-shrunk.’ If denim is not sanforized, it’s referred to as ‘unsanforized’ or ‘shrink-to-fit.’ But few jeans are truly unsanforized (even Levi’s shrink-to-fits are sanforized a little bit).

Sanforization solves a fundamental problem of unfinished denim: it eliminates shrinkage. It makes buying a right-sized pair of jeans a whole lot easier.

Indigofera Clint Shrink-to-Prima-Fit before and after
Shrink-to-fit jeans before and after shrinkage.

Sanforized denim shrinks about 2-3% (although it can be more) while unsanforized denim shrinks as much as 10%. The shrinkage is more noticeable in the legs, which are relatively longer than for instance the waist.

Many denimheads prefer unsanforized denim because of how it looks and fits. The beauty of unsanforized jeans is that they mould to your body in a way sanforized jeans simply won’t. What you get is a truly personalised fit. Some also enjoy the ritualised process of shrinking their jeans themselves.

Levi's LVC 1944 501 shrink to fit before and after
Same jeans, before and after shrinkage

How denim is sanforized

Sanforization was invented in the late 1920s by American businessman and inventor, Sanford L. Cluett. Essentially, it’s a mechanical compaction process for woven fabrics.

The fabric is fed in between two hot roll bars on top of a stretchy endless rubber belt. The fabric is first moistened, usually by steam. This lubricates the fibres and primes shrinkability.

As the rubber returns to its original length once through the cylinders, the warp yarns shrink and the weft yarns are packed closer together. After the fabric leaves the rubber belt, it enters a dryer, which locks the fibres in their shrunken state.

Without sanforization, jeans might not have become the global phenomenon it is today, simply because a lot of consumers wouldn’t want to go through the trouble of shrinking their jeans themselves.

Then again, it’s not only denim that’s sanforized. Virtually any woven fabric these days is pre-shrunk. Nevertheless, it’s an important fabric finish that makes jeans shopping a lot easier.

Sanforization process

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