The soft, mellowed look a rug's natural dyes acquire over decades of use and light, as the colors settle into subtler, more harmonious tones that mellow rather than merely fade; the wool also grows softer and loose fibers wear away, so the pattern reads more sharply. It is fullest in antique rugs and is treated as a mark of genuine age. Artificial aging treatments imitate it but tend to give a bleached look with an abrupt band of color in the fiber instead of a gradual fade from tip to base.