Abrash is color change in the face yarns of a rug due to differences in wool, dye lots or mordants used in the dying process. The color change occurs across the width of the rug, left to right, parallel to a weft yarn. Close observation at the back clearly shows the color change along a row of knots. Color change due to other reasons such as fading are irregular and follow no particular pattern.
Abrash can vary from subtle differences in shade to dramatic differences in color. Subtle abrash can be obscured by soil and becomes more apparent after cleaning but a quick look at the back will confirm abrash.
Abrash is a characteristic of hand-woven textiles and does not, in itself, increase or decrease the value. In fact, some manufacturers of both hand and machine-made rugs intentionally weave abrash into their rugs. Abrash can enhance the beauty and desirability of a rug.
Unlike abrash, variegated yarns are dyed in sections with more than one color. The yarn has color variations throughout the entire skein and creates interesting effects.