How do you tell silk from wool in a rug?
Silk rug fiber is microns thick, lustrous and reflective, cool to the touch, and produces a tight black ash when burned. Wool fiber is coarser, warmer to the touch, and burns with a strong scorched-hair odor leaving a brittle ash. Knot density also separates them — silk pieces typically exceed 600 knots per square inch; wool rarely does. Five concrete tests will tell you in under a minute.
Five tests separate silk from wool.
Walk around the rug under a single light to read luster, touch the pile for temperature and oil, turn it over to count knots per square inch, weigh it for density, and burn a single yarn from the back. Together, the five tests confirm fiber with near-certainty in under a minute.
- Silk shifts color with angle; wool stays flat under any light.
- Silk feels cool and smooth; wool feels warm and faintly oily.
- Silk: 600 to 1,500 knots per in²; wool: rarely over 400.
- Silk is lighter per square foot than wool of the same size.
- Burn test: silk smells soft, wool smells of scorched hair.
The five tests, in order.
Each step takes seconds. Done together, they tell you whether the pile is silk, wool, a blend, or a synthetic imitation.
- 01
Look at the luster from different angles.
Tilt the rug under a single light source and walk around it. Silk reflects light directionally — the color shifts visibly as your angle changes, going from light to dark with the lay of the pile. Real silk almost shimmers. Wool, even fine wool, reflects light diffusely and stays close to the same tone from every angle. If the rug changes character as you walk past it, you are likely looking at silk.
- 02
Touch the pile and feel temperature and oil.
Lay your palm flat on the pile for ten seconds. Silk feels cool to the touch, smooth, almost slippery — its fibers do not insulate the way wool does. Wool feels warm immediately, slightly oily from natural lanolin still in the fiber, and resists your hand. The temperature difference is subtle but unmistakable once you have felt both side by side.
- 03
Inspect the knot density on the back.
Turn the rug over and count the knots in a one-inch square. Silk rugs typically run from 600 to well over 1,000 knots per square inch — Qum and fine Hereke pieces can reach 1,500. Wool rugs rarely exceed 400 knots per square inch even on the finest workshop pieces. If the knot count looks impossibly fine, the fiber is almost certainly silk or a silk-wool blend.
- 04
Weigh the rug in your hand or against another.
Silk has a much lower density than wool, so a silk rug weighs noticeably less per square foot than a wool rug of the same dimensions. Pick up a corner and compare to a wool rug you know. Silk feels almost weightless for its size; wool has body. The weight test alone is not diagnostic, but combined with the other four it confirms.
- 05
Perform a controlled fiber burn test on a single yarn.
The most reliable test. Pull one yarn from the back of the rug (never the front), hold it with tweezers over a sink near a flame for two seconds, and observe the burn. Wool burns reluctantly, smells of scorched hair, leaves a brittle black ash that crumbles. Silk burns slowly with a softer smell, leaves a tight dark ash. Synthetic shrinks, smells of plastic, leaves a hard bead. See our full burn-test guide before attempting.
Four cues that confirm the fiber.
No single test gives certainty. A fine wool Nain can shimmer under raking light. A silk-and-wool Isfahan will read partly cool and partly warm in the hand. A mercerized cotton imitation can pass the luster and touch tests until the moment you burn it. What identifies fiber correctly is the convergence of multiple cues, read together.
Use the four entities to the right as a quick checklist. If luster, hand, knot density, and burn behavior all agree, the fiber identification is reliable. If they conflict — cool to the touch but only 200 knots per inch, for example — the rug is likely a blend or an imitation, and worth a closer look by an expert.
Where most silk-vs-wool reads go wrong.
Confusing mercerized cotton or art silk with real silk.
Mercerized cotton is treated to shimmer like silk and is often used in low-cost rugs sold as silk. Burn tells the truth: mercerized cotton burns fast and smells like paper, not scorched hair or soft silk. Art silk (rayon viscose) shrinks and smells of burned plastic. Real silk is a protein fiber and burns like one.
Trusting a salesperson's word over the back of the rug.
A silk-content claim should always be verifiable. Turn the rug over, count the knots, feel the foundation, and burn a single yarn from the back if you have any doubt. Reputable dealers welcome the test; pressure to skip it is a sign to walk away.
Assuming silk highlights mean a fully silk rug.
Many fine Persian wool rugs — Nain, Isfahan, Tabriz — use silk highlights to outline floral detail on a wool ground. These are silk-and-wool rugs, not pure silk. Pure silk pieces (Qum, Hereke) are entirely silk, foundation and pile. Both are valuable, but they are different categories.
Treating a silk rug like a wool rug.
Pure silk requires different cleaning than wool — gentler soap, cooler water, no rotary contact, and individual handling. A standard machine wash will destroy a silk Qum. If the test confirms silk, the cleaning approach changes entirely.
Once the fiber is silk, the cleaning changes.
A silk rug cannot be cleaned the way a wool rug can. Standard rotary machine processes felt silk into ruin in minutes, alkaline soap destabilizes its dyes, and excess water deforms the foundation. If your tests point to silk — or to a silk-and-wool blend, common in Nain, Isfahan, and Tabriz workshops — the cleaning approach changes entirely.
The Cohen family has hand-washed silk Qum, Hereke, and antique Isfahan pieces for more than a decade. Bring us your rug for a complimentary fiber identification and wash quote. By hand, in our atelier, returned to your home in better condition than the day it left.
Continue your reading.
The Rug Fiber Burn Test
Step-by-step protocol for safely burn-testing a single yarn from the back of a rug. Identifies silk, wool, cotton, and synthetic.
How to Identify a Persian Rug
Seven tests for verifying a real hand-knotted Persian. Knot type, fringe, wool, dye, design tradition, and weave direction.
Silk Rug Cleaning
Hand-washed silk rug cleaning by our master artisans — Qum, Hereke, Isfahan silk, and antique silk pieces in our atelier.
Letters from across the Northeast.
A few of the rugs we've cared for — and the families who trusted us with them.
“They returned an heirloom Tabriz — the colors look exactly as my grandmother described them.”
“A 1920s Heriz I thought was beyond saving came back better than the day my parents bought it.”
“Our clients trust us with eight-figure homes. Horizon is the only atelier I send their rugs to.”
More from Horizon.
Other ateliers, every service we offer, and the rest of our story — a few directions to explore.
Bring us the rug. We will identify the fiber.
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