Heavy Abrash is caused by the change over to a new dye batch. Generally Abrash is desirable in tribal carpets and undesirable in urban carpets. A Turkic speaking nomadic group living mostly in southern Iran known for fine quality of their rugs. The city that shares the name of The Ardebil Carpet one of the finest and most famous objects of Islamic art. There is controversy, though, as to whether the carpet was actually made there.
Modern era carpets from the region are generally of dubious quality.
ART SILK Also called artificial silk it describes a yarn for weaving made from mercerized cotton that attempts to take on the appearance of silk. The fiber is very soft to the touch and is used to create a price category for smaller budgets whose tastes run toward expensive silk rugs. Rugs sold as silk as given a burn test to check for the presence of cotton. Fine flat carpets woven in France from the 15th to 19th Centuries. They were derived from Moorish weaving with the assistance of Architects and Artists of the royal court.