What is a Knot Density?
Knot density, also known as knot count, is an important factor in understanding the quality and value of hand-knotted rugs. It refers to the number of knots tied per unit area, typically measured in knots per square inch (KPSI) or knots per square centimeter (KSPC).
How Knot Density Impacts on the Rug Quality?
Knot density (KPSI) is a major factor influencing rug quality, High knot density is a good indicator of quality, especially for rugs with intricate designs.
Higher knot density generally indicates a finer quality rug. With more knots per square inch, the weave becomes tighter, resulting in:
Increased durability: A denser weave creates a more robust structure, making the rug more resistant to wear and tear.
Intricate designs: A higher knot count allows for finer details and more elaborate patterns.
Luxurious feel: Denser rugs often feel softer and plusher underfoot.
Lower knot density doesn't necessarily mean a bad rug. Here's why:
Certain styles: Some traditional rug styles, like nomadic rugs, are known for having a lower knot density due to their focus on geometric designs and practicality.
Thicker pile: Rugs with a lower knot count might have a thicker pile, making them more comfortable underfoot.
Rug's age: Very old rugs might have a lower knot density due to the old weaving techniques of the time.
What is the formula of the Knot Density?
Knot Density (KPSI) = Number of Vertical Knots per Inch x Number of Horizontal Knots per Inch.
How to Measure the Knot Density of a Rug?
Here's how to measure the knot density (KPSI) of a rug:
Tools:
- A ruler (preferably with a one-inch square section)
- A magnifying glass (optional, but helpful for detailed rugs)
Steps:
Flip the rug over: Examine the back of the rug, where the knots are visible.
Identify the knots: Each knot will appear as one or two bumps (depending on the knot type) on the vertical threads (warps) of the rug.
Locate a flat, undistorted area: Avoid fringes or borders, as knot density might differ there.
Use the Ruler:
- Place the one-inch square section of the ruler on the back of the rug.
- Count the number of horizontal knots (across the width) within that one-inch area.
- Repeat for vertical knots: Now, rotate the ruler by 90 degrees and count the number of vertical knots within the same one-inch square area.
- Multiply the counts: Multiply the number of horizontal knots by the number of vertical knots. This gives you the KPSI for that specific spot on the rug.
Example: If you count 10 vertical knots and 8 horizontal knots in your 1-inch square, the KPSI would be 80 (10 x 8).
Tips
Take multiple measurements in different areas of the rug and average them for a more accurate overall KPSI.
Use a magnifying glass for a clearer view of the knots, especially with intricate designs.
Be aware that some rugs might have varying knot densities throughout, particularly handmade ones.
How to Calculate Knot Density on a Rug?
KPSI (Knots Per Square Inch) tells you how tightly woven a rug is. To calculate this, we count the number of knots on the back of the rug within a one-inch square area. The more knots per square inch, the higher the KPSI and generally, the finer the quality of the rug.
For instance, a well-made rug might have a KPSI of around 200 (20 knots horizontally x 10 knots vertically in a one-inch square). A very high-quality rug, known for intricate details, could reach a KPSI of 400 or more.
What is a Good Thread Count for The Persian Rugs?
Typically a good thread count of Knot density for a Persian rug ranges from 25 to 1000 KPSI. Here you can see below.
Understanding KPSI Ranges:
Below 80 KPSI: Considered low density, often associated with simpler designs or older rugs.
120 to 330 KPSI: Medium to good density, offering a balance between durability, detail, and affordability.
Above 330 KPSI: Very good for high density, known for intricate designs and a luxurious feel.
Conversion Table (KPSM to KPSI):
| KPSM Range | KPSI Range | Description |
| 40,000-80,000 | 3.72 - 7.43 | Very Coarse |
| 80,000-120,000 | 7.43 - 11.15 | Coarse |
| 120,000-240,000 | 11.15 - 22.30 | Medium |
| 240,000-360,000 | 22.30 - 33.45 | Somewhat Fine |
| 360,000-500,000 | 33.45 - 46.45 | Fine |
| 500,000-1,000,000 | 46.45 - 92.90 | Very Fine |
| 1,100,000 or higher | 102.20 or higher | Extraordinary Fine |