輕松英語(yǔ)閱讀：彈力牛仔褲

Remember how stiff jeans used to be? In the olden days, even sitting down or climbing stairs was hard. But these days jeans can be skintight yet surprisingly comfortable. The secret is the spandex, which they add to denim to make it stretchy and comfortable.

However, this comfort comes at a price. Believe it or not, our love of stretchy jeans has lead to a shortage in the materials used to make American money.

Until recently, one of the main materials in American money was leftover denim from jeans manufacturers. The leftover denim was bleached, turned into pulp, and finally it was made into bills.

printing money

Nowadays, spandex is added to most denim to make it comfortable. Denim with spandex is unusable for paper-making. As a result, the company that prints US money has to find other sources of cotton fiber. This switch has been difficult but these days they are mainly using natural fiber—not recycled.