Why most jeans are blue

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December 19, 2017 6:27 PM

The indigo dye was chosen for the way it interacted with cotton.

When was the last time you can remember that blue jeans were out of fashion? These pants have become an American icon, but how did they get that blue color in the first place? Following is a transcript of the video.

People have been wearing blue jeans for centuries. Originally, the blue color came from a natural indigo dye. The dye was chosen for the way it interacted with cotton. When heated, most dyes penetrate the cotton fibers but indigo dye attaches to the fiber's surface, instead. The result? During each wash, some of the fibers and dye molecules escape, giving jeans that signature faded look over time.

Today, jeans are dyed with a synthetic indigo dye. Take a closer look and you'll see a clever design. The warp thread is dyed but the weft thread is left white. This reduces the amount of dye needed for each pair of jeans. It's also why many jeans are blue on the outside but white on the inside. Each pair of jeans requires 3-12 grams of dye. Each year, we produce several hundred thousand tons of indigo dye. Most of that is mused for making blue jeans. Do the math, that's between 90 million to 2.2 billion new jeans per year. Looks like this fashion trend will stick around for a while.

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