“White Knots” is a term used in the rug trade to describe a condition inherent in hand knotted rugs, where light colored spots appear over time, seemingly at random, in the body of the rug pile. These spots are knots in the rug’s foundation that have worked their way through the rug pile and are showing through the pile yarns.
When a hand knotted rug is made, its foundation is made of warp and weft yarns. Warp yarns run the length of the rug and weft yarns span the rug’s width. Often the material the weaver has on hand is too short for the length needed, so shorter lengths are tied together until the necessary length is achieved. Also, in the weaving process some warp yarns can break, and the loose ends have to be tied together, the knots used in all of these instances will eventually become white knots.
When a rug is new and its pile is at full length, these knots can be hidden from view, but eventually regular foot traffic will wear the pile length down and begin to expose them. Although the term “white knots” is used generally, their appearance reflects the material used in the foundation of a rug, so depending on the material used, your rug might have "blue knots” “gray knots” or others. It is important to understand when you begin to notice them that these knots do not indicate that there is a defect, or lack of quality with a particular area rug, rather they simply reflect how your rug was made. They should never be cut as this will lead to a hole in the foundation of your rug.
Through foot traffic and regular soiling, these knots can become darker and less noticeable. With a thorough cleaning, the soils and stains that help to hide the knots will be removed, and the knots will reappear or become more noticeable. This does not mean there is a problem with the cleaning, but again reflects one of the physical characteristics of hand knotted rugs as they wear. If their appearance is particularly bothersome, your cleaning professional may be able to lightly tint them after cleaning as an additional service, but keep in mind that with regular use, your rug will gradually become soiled again and the knots will gradually disappear until the next cleaning.