Pumice and Stone-Washed Jeans

Stone-washed jeans really are washed with stones. And acid-washed jeans are washed with…stones!

Stone-washed jeans first became popular in the 1970s because of their faded, vintage look and because their denim was much softer than stiff new jeans.

To “stone-wash” jeans, they are placed in a horizontal, industrial-sized clothes washer along with a bunch of pumice stones. As the washing machine rotates, the jeans are pounded by the tumbling stones, creating that “worn-in” look.

Acid-washed jeans, which first became popular in the 1980s, are made in a similar way. The jeans are put in an industrial washing machine, without water this time, along with pumice that has been dampened with a weak solution of bleach. As the pumice tumbles on the denim, the bleach gives the jeans a unique colour and pattern. The bleach is sometimes replaced with potassium permanganate but the effect is the same.

Despite the name, no acid is used in making acid-washed jeans.

Pumice forms when lava contains lots of gas bubbles that make it frothy. As the lava-foam cools and hardens, the bubbles are trapped in the rock.

Pumice is the only rock that floats but, like a sponge, it absorbs water until it eventually becomes saturated and sinks.