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All About Oriental Carpets’ Knot Density

If you’ve been looking at antique Oriental or Persian carpets, then you have probably heard of the term knot per square inch (or centimeter) or knot density – and perhaps wondering what it is.

Knot density is one traditional way of determining the quality of handwoven rugs. It is the number of knots per square area. For example, knots per square inch, or “kpsi,” is simply the number of knots for every square inch. A carpet’s knots are counted on its backside per linear inch, centimeter, or decimeter along its warp and weft – which are visible on the backside. Then, these two numbers are multiplied.

A rug’s knot density is one way of determining its value. However, it is not always true that a carpet with a very high kpsi is valuable or of high quality. While knots play a role in the quality of workshop- and city-made rugs, the same is not always valid for nomadic and village carpets. Other factors are considered to determine their quality, such as how the design is created from the weaver’s memory and the dyes and materials used, and more. This is because workshops and city weavers have access to more sophisticated tools, and nomadic groups typically migrate often and do not always have the time to weave high-density knots.

Nomadic and village rugs usually have 25 to 100 kpsi. On the other hand, workshops and city rugs can have up to over 1000 kpsi. Not only do they have better tools, but they can also draw cartoons to use as their pattern.

So, does the knot density matter in the rug’s value?

Yes and no! You cannot only use knot density alone as the determining factor of a rug’s quality. But, if you compare two rugs of the same origins and from the same category and have other similar quality factors, knot density can help you tell which of those two is more valuable.

Here is something to think about: an authentic vintage Persian and Oriental carpet; every knot is hand-made. It takes a highly skilled weaver; on average2 or three weavers usually make this size rug about ten seconds to tie a knot (taking into account the running of the warp), which means six knots per minute or 360 knots per hour. A skillful rug weaver will take 6,480 hours to weave a 150 kpsi, 9 x 12-foot rug if you do the math. If the weavers work 8- hour shifts, that means it will take someone 810 days or two and a half years to finish the carpet. Two or three weavers usually make this size rug, so the number of hours can be divided into two or three.

That is how much work is put on every handwoven rug. Ask about the rug’s knot density the next time you go rug hunting, or visit us at Sharafi & Co, and we’d be happy to walk you through the kpsi of the rugs that you like.

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