You might have heard this odd advice from fashion gurus before – “don’t wash your jeans!” But why? Is it real advice, or just a prank pulled on unsuspecting, dim-witted denim rubes?
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Here’s the thing: whether you’re wearing a pair of busted Levis or brand-new raw denim from some fancy boutique, your pants are part of a debate that designers and customers alike have been having for decades: When should you wash your jeans? Do you need to wash them at all?
Let’s look at the basics. Denim is a kind of cotton with a twill textile weave. Check out this photo: in a twill weave, the thread called the weft – the crosswise yarn - passes under at least two warp threads – those are the lengthwise yarns. In most jeans, only these warp threads are dyed, meaning that these other threads, the weft threads, remain white. That’s why blue jeans are white inside. That blue shade on the warp threads comes from a dye called indigo. Unlike some other dyes, indigo doesn’t penetrate the cotton. Instead, it sits atop the yarn, on the surface of each thread. Over time, molecules of indigo chip away, causing the fabric to fade. This fade makes each pair unique, so much so that the FBI analyzes denim patterns when tracking criminals. The more you wear a pair, the more broken in they become.
You’ll see the appearance of fade patterns. Whiskers on the front, honeycomb patterns behind the knees and so on. And here’s where it gets – oh, wait. Wrong show. Not all jeans are created equally. Let’s divide them into two rough categories – washed and raw. Washed denim is just that – washed after dyeing, to make the fabric softer and reduce shrinkage. Sometimes washed denim is artificially distressed to give it a broken-in or worn look. The fading of raw denim, on the other hand, happens naturally over time depending on the daily activities of the person wearing the jeans. The longer you go without washing these jeans, the more pronounced fading patterns will become, personalizing the pants. Once you have a pair of jeans, you’ll hear numerous pieces of advice about caring for them.
Most of this doesn’t apply across the board. For example, companies like Hiut denim will ask you to wait at least 6 months before washing your jeans, because if you wash them early the indigo will wear off uniformly, robbing you of those unique fade patterns. And this is the heart of the whole “to wash or not to wash” question. The longer you go without washing a pair of jeans, the more pronounced the wearing pattern becomes. You’ll also preserve the indigo, as well as the stiff texture of the fiber. But what happens if you don’t wash them? Won’t bacteria pile up, turning your lower hemisphere into a plague-ridden cesspool of filth? Not necessarily.
In 2011 a microbiology student at the University of Alberta went, get this, 15 months without washing his jeans. He tested their bacterial content, along with the bacterial content of another pair that had been washed about two weeks beforehand. He found almost no difference. So if you can’t wash them, what do you do to keep your blue jeans clean? You’ll hear some crazy stuff. Levi’s famously recommended freezing your jeans to kill bacteria and stave off any funky odors, but microbe expert Stephen Craig Cary says that’s a myth. Most bacteria in our pants comes from our skin, and a lot of these organisms are preadapted to low temperatures. Cary recommends using high temperatures – think 121 degrees Celsius for ten minutes – to rid the denim of bacteria. Or, he adds, just wash them. So, depending on how often you wear your jeans, their age, the denim type and what you do while you’re wearing them, you really don’t have to wash them as often as, say, your underwear. If you want to get that uber-cool unique fading pattern, your best bet really is to avoid washing them for awhile, even if you have to soak them first to shrink them.