An expert test of dye type and age: the pile is parted or folded and viewed from its tip down to the base where it meets the foundation. Color that grows darker toward the base usually means a synthetic dye that has faded from light exposure at the top, dating the rug to the late 19th century or later. Natural dyes, almost universal before the 1860s, fade gently and evenly, whereas color treated to look old tends to look bleached and shows a sharp band midway down the fiber.