A condition where areas of carpet appear lighter or darker than surrounding areas due to light reflecting differently off pileThe surface of a rug or carpet, made of upright fibers in cut tufts or loops. In a hand-knotted rug it is formed by the cut ends of thousands of wool or silk knots tied onto the warp row by row, trimmed lightly during weaving and given its final height by shearing at finishing. Pile thickness, measured from the back of the rug to the top of the pile, typically runs from low, about 1/8 to 1/4 inch (3 to 6 mm), to high, about 1/2 to 5/8 inch (13 to 16 mm). Fine, dense designs are cut short to keep the pattern sharp; higher pile suits traffic and heavy furniture, lower pile suits door clearance and humid rooms. fibers that have changed direction. Not a manufacturing defect but a physical characteristic of cut pileA carpet construction where the loops of yarn are cut at the top, creating a plush surface with individual tufts standing upright. carpets. Also known as watermarking or pooling.