(Posted on 19/09/18)
Persian carpets are famous for a luxurious thick pile or carpet surface (the stuff you run your fingers and toes through) that's made by weaving with an important step added. During weaving, many hand-tied knots are added in rows to the warp threads. Then weft threads are interlaced above them and packed down with a comb to hold the knots in place.
The knots form the surface texture and image. Knot density, or the number of knots used within a square inch area, varies by region and rug type. It can sometimes signal a very high quality rug.
Another factor involving knots is knot type, or how the knot is tied to warp threads. It also tends to vary according to the geographic area in which the rug is made.