Denim is a sturdy cotton twill in which the warp threads are dyed indigo while the weft stays white, giving the characteristic blue face and paler reverse. Born as a workwear cloth (hence the jeans of gold miners and cowboys), denim became a universal symbol of the democratic fashion of the twentieth century. It is prized for its durability and for the way it 'ages' handsomely, acquiring individual fades and wear. Denim weight is measured in ounces: light for shirts and dresses, heavy for rigid jeans and jackets. It may shrink and bleed on first washing.