Occasionally a client will call and ask us to explain the appearance of white knots in their rug after we return it to them after a professional cleaning. Did the professional rug cleaning somehow do something to the structure of the rug that somehow created white knots? No. The fact is that white knots that become visible after a professional cleaning were always there in the rug; it is just that a thorough professional cleaning removes the dirt or dust that masks their appearance and which allows them to blend into the field of the rug unnoticed. Below is a photo of a cleaned rug with some white knots visible in the pile:
But why are those white knots in a rug in the first place?
White knots (which are sometimes different, less noticeable, colors) are usually a product of one of two things. First, they are a byproduct of having limited available materials during the weaving process. White knots are actually part of the warp of the rug. Warp yarns are the vertical yarns which are affixed to the loom. In the picture that I took below of a weaver in a village near where I grew up in central Anatolia, the white cotton yarns are the warp of the kilim that is being woven:
As you can see from the photo, quite long white cotton yarns are needed for the warp. In a larger rug, the warp will obviously be even longer. Sometimes, weavers do not have access to very long continuous yarns so they have to tie different strands of yarn together - thereby forming a white knot. Sometimes the white knots are pushed to the back of a rug so that they are less visible on the face of the rug. Other times they are left on the face of the rug but they are not noticeable because foot traffic soils the cotton so that it eventually blends into the field of the rug. Other times the white knots are not visible because they are buried within the knots of a rug. However, over the years when the knots - the pile - become worn (and therefore shorter), the white knots become visible. They don't suddenly form - they were always there, but the shorter pile now makes them visible.
The second reason why a rug (or kilim) sometimes has white knots is because during the weaving process, the weaver pushes down her knots with a beater comb and by doing so sometimes tears the warp strings. When the weaver does this, she or he has to tie another warp string to the broken warp so that the weaving can continue. Some view broken warp strings as a sign of a weaver's inexperience. Others view broken warp strings as a sign of inferior quality of the warp's material. The truth is that it would be impossible to weave an entire rug without occasionally tearing some warp strings or having to join a few warp strings together. The white knots, therefore, are the inevitable byproduct of having a rug made entirely by hand.
We did receive one call, however, from a client who had just purchased a rug and was worried about the "white knots" that she suddenly spotted in her rug. Her use of the term "white knots" led us to believe that what she was referring to was the simple warp joining that we described above. However, that was not the case. The "white knots" that she described were actually moving and were not white knots at all. They were actually moths!