A few words about KPSI or KPI knots per square inch or knots per inch. The quality and price of a handmade oriental rug is often determined by the amount of time a weaver has to spend to knot the rug. Of course this is only one element in an antique rug to determine value. Other determining factors such as rarity, wool quality, design complexity, desirability, condition etc all come into play in the market as well. If you look at the backside of a rug and have a ruler handy you can determine the knot count by counting the knots horizontally across one inch and making note of that figure then counting the knots vertically by one inch. Multiply the two figures together and you will get the KPSI. The higher the knot count the tighter the weave and the finer the rug. BTW: An American Quarter coin measures roughly one inch across so you could throw that down to count the knots.
Rug weavers in general while working on a loom sitting side by side with three weavers working on a 9’x12’ rug could tie 18,000 knots per day. It could easily take these weavers 4 months working full time to weave a 9’ x 12’ rug.
The Back of A Turkish Sivas Rug
The Back of A Hadjili Tabriz Persian Rug ~ These are known for their exceptionally high knot count! Can you see the difference?