Rugs dyed with natural dyes sometimes have abrash, a term used to describe the slight variations in the shad of a single color within a rug. These variations typically appear in a horizontal line. Abrash can occur when a weaver uses wool that was unevenly dyed, or when the weaver uses wool from different dye lots.
The word used to describe the variations in color found within a single color in an Oriental carpet. ABRASH is commonly seen in tribal nomadic rugs and in some modern reproductions. ABRASH is caused by variations in yarn diameter native to nomadic dyeing and yarn spinning, the change over to a new dye batch, and the amount of lanolin present in the wool. Generally ABRASH is desirable in tribal carpets and undesirable in urban carpets.
Inadvertent variations in color found within a field of color in an area rug. Abrash usually appears as tonal stripes running horizontally across the rug. Subtle instances of abrash are caused by natural variations in yarn diameter caused by hand-spinning, while heavier appearances of abrash are caused by switches of the dye batch. Since abrash is a natural effect of hand-weaving, and is sometimes an intentional attempt by the weaver to add interest to monotonous open-field backgrounds, it is generally seen as a desirable feature of tribal rugs.