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Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,

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Speaker 1: I'm more in Volke Bob and today's episode is another

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Speaker 1: classic from the vaults. Our earstwhile host Christian Sagar is

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Speaker 1: here to present the scientific side of a fashion argument

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Speaker 1: that keeps cropping up? Do you really need to wash

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Speaker 1: your jeans? Hey, brain stuff, I'm Christian Sagar, and not

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Speaker 1: to get too personal, but when did you last wash

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Speaker 1: your jeans? You don't have to tell me if you

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Speaker 1: don't want to. But here's the thing. Whether you're wearing

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Speaker 1: a pair of busted Levies or brand new raw Denham

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Speaker 1: from some fancy boutique, your pants are part of a

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Speaker 1: debate that designers and customers alike have been having for decades.

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Speaker 1: When should you wash your jeans? And do you need

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Speaker 1: to wash them at all? Well, let's look at the basics.

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Speaker 1: Denham is a kind of cotton with a twill textile weave.

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Speaker 1: In a twill weave, the thread called the weft that's

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Speaker 1: the cross wise yarn, passes under at least two warp threads,

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Speaker 1: and those are the lengthwise yarns. In most genes, only

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Speaker 1: these warp threads are dyed, meaning that these other threads

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Speaker 1: the weft threads remain white. That's why blue jeans are

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Speaker 1: white on the inside. That blue shade on the warp

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Speaker 1: thread comes from a dye called indigo, and unlike some

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Speaker 1: other dyes, indigo doesn't penetrate the cotton. Instead, it sits

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Speaker 1: atop the yarn on the surface of each thread. Over time,

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Speaker 1: molecules of indigo chip away, causing the fabric to fade.

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Speaker 1: This fade makes each pair unique, so much so that

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Speaker 1: the FBI analyzes denom patterns when tracking criminals. Yeah, that's

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Speaker 1: a real thing. The more you wear a pair, the

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Speaker 1: more broken in they've become. You'll see the appearance of

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Speaker 1: fade patterns, whiskers on the front, honeycomb patterns behind the knees,

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Speaker 1: and so on. Not all genes, however, were created equally.

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Speaker 1: Let's divide them into two rough categories. Is washed and raw.

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Speaker 1: Washed Denham is just that washed after dying to make

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Speaker 1: the fabric softer and reduced shrinkage. Then, in a process

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Speaker 1: called sandforrization, the trousers are moistened, steamed, and stretched to

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Speaker 1: reduce the shrinkage rate. Most genes are sanforized these days.

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Speaker 1: Raw or dry denham can be saporized or unsanforrized. If

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Speaker 1: it isn't, it can shrink up to ten percent when washed. Sometimes,

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Speaker 1: washed denham is artificially distressed to give it a broken

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Speaker 1: in or worn look. The fading of raw denham, on

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Speaker 1: the other hand, happens naturally over time, depending on the

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Speaker 1: daily activities of the person wearing the jeans. The longer

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Speaker 1: you go without washing these genes, the more pronounced fading

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Speaker 1: patterns will become. Personalizing your pants. Once you have a

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Speaker 1: pair of jeans, you'll hear numerous pieces of advice about

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Speaker 1: caring for them. Most of this doesn't apply across the board.

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Speaker 1: For example, companies will ask you to wait at least

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Speaker 1: six months before washing your jeans because if you wash

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Speaker 1: them early, the indigo will wear off uniformly, robbing you

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Speaker 1: of the unique fade patterns. And this is the heart

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Speaker 1: of the whole to wash or not to wash question.

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Speaker 1: The longer you go without washing a pair of jeans,

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Speaker 1: the more pronounced the wearing pattern becomes. You'll also preserve

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Speaker 1: the indigo as well as the stiff texture of the fiber.

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Speaker 1: But what happens if you don't wash them. Won't bacteria

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Speaker 1: pile up, turning your lower hemisphere into a plague written

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Speaker 1: cesspool of filth. Well, not necessarily in. A microbiology student

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Speaker 1: at the University of Alberta went get this fifteen months

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Speaker 1: without washing his jeans. He tested their bacterial content along

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Speaker 1: with the bacterial content of another pair that had been

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Speaker 1: washed about two weeks beforehand, and he found almost no difference.

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Speaker 1: So maybe it's more that everything we wear is already dirty.

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Speaker 1: So if you can't wash them, what do you do

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Speaker 1: to keep your blue jeans clean? Well, you're gonna hear

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Speaker 1: some crazy stuff. Levi's famously recommended freezing your genes to

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Speaker 1: kill bacteria and stave off any funky odors, but microbe

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Speaker 1: expert Stephen Craig Carry says that is a total myth.

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Speaker 1: Most bacteria in our pants comes from our skin, and

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Speaker 1: a lot of these organisms are preadapted to low temperatures.

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Speaker 1: Carry recommends actually using high temperatures think a hundred and

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Speaker 1: twenty one degrees celsius for ten minutes to get rid

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Speaker 1: of the denom or bacteria or you know. He adds,

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Speaker 1: you could just wash them. So depending on how often

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Speaker 1: you wear your jeans, their age, the denom type, and

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Speaker 1: what you do while you're wearing them. You really don't

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Speaker 1: have to wash them as often as say you're underwear.

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Speaker 1: If you want to get that uber cool, unique fading pattern, though,

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Speaker 1: your best bet really is to avoid washing them for

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Speaker 1: a while, even if you have to soak them first

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Speaker 1: to shrink them. And regardless of how carefully you care

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Speaker 1: for your favorite pair of raw Denom jeans, messes like

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Speaker 1: life find a way one day, some sort of disaster

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Speaker 1: will strike and you'll have to clean your jeans somehow, yes,

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Speaker 1: even if that means washing them. Today's episode was written

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Speaker 1: by Ben Bollin and produced by Tyler Clang. For more

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Speaker 1: on this and lots of other topics, visit our home planet,

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Speaker 1: how stuff Works dot com