Rug Construction and Cleaning


When rug cleaners who clean relatively few rugs hear of rug construction types such as Qum, Baluch or Bokhara, they may feel overwhelmed and wonder why the details of how and where a rug was made are relevant to their cleaning process.

Certainly, the ability to discuss rug identification intelligently helps gain a client’s trust and will undoubtedly help one gain more business, but for cleaning does it matter if a rug is single-wefted?

While there are many qualified rug experts in the world, what I want to do is provide the basics and show you how they relate to cleaning.

Natural or synthetic?

Just as with carpet or upholstery, a simple burn test will reveal if a fiber is synthetic or natural. The most common synthetic face fiber will be olefin. The most common natural fiber is wool, but you may encounter silk, rayon, cotton or some others. Knowing the specific fiber is not as important as knowing if it synthetic or natural. But you will want to learn to know silk when you see it. Sometimes cotton or rayon will be misidentified as silk, although it is really art (artificial) silk or faux silk.

  • Cotton burns quickly. While burning it smells like burning paper. The smoke is gray or white. It leaves no melted bead, just gray ash. The ash is fine and soft and can be easily crumbled.
  • Rayon has a rapidly burning orange flame. It may also smell like burning paper. It usually burns completely and leaves no ash or might leave a slight amount of soft gray ash.
  • Silk burns slowly and curls away from the flame. It does not melt but does produce a dark bead which can be easily crushed. It is self-extinguishing and leaves ash that is a dark, gritty, fine powder. It smells like burned hair. It gives out little or no smoke.

Wool and other natural fibers will need to be cleaned with a product approved for such fibers, for example, those approved by WoolSafe.

Many rugs with synthetic face fibers will still have foundation yarns of natural fibers, especially cotton.

Pile yarns or flat woven?

Flat woven rugs may be called Dhurries if they originate in India; Kilims if they originate almost anywhere in the Middle east; and Navajo if they are woven by Native Americans, mainly in Arizona and New Mexico.

Traffic on flat woven rugs is on the sides of the fibers rather than the tips. There is no cushion of pile to protect the foundation yarns. Under equal traffic loads, flat woven rugs will show wear and abrasion more readily. Cleaning does not correct wear. Be sure to keep expectations reasonable.

Flat woven rugs contain less yarn and require much less labor to produce since there are no knots to tie. Generally they will be less expensive, but there are some very pricey Navajo rugs. Hopefully these are being displayed and protected and not used as a mat at the front door.

Any rug may curl depending upon edge treatments such as binding, serging and side cords. But, in my experience, flat woven rugs have a greater tendency to curl than pile rugs. You may need to block them to help them hold their shape during cleaning and drying. Your inspection may reveal repairs that need to be made. This can be a good upsell. Make sure any problems are noted on your inspection form so you aren’t blamed for causing them.


There are two common types of knots used to create the pile — symmetrical knots (also known as Turkish or Ghiordes) and asymmetrical (also known as Persian or Senneh). The symmetrical knot can be recognized by the ‘collar’ around the warp yarns when viewed from the surface. In hand-woven rugs the knots will be tied around the warp yarns.  In machine made rugs it is common for the pile to be affixed to the weft yarns.

It is possible to have only one weft yarn between each row of knots.

There is another type of knot, often called a Jufti. This is simply a variation of one of the previously mentioned knots, but it is wrapped around three or four warp yarns. Why would the weaver tie the knot around several yarns? You probably guessed that with this knot there are fewer knots in a row, which means less yarn and much less time and labor.

With less pile yarn, the rug will appear to wear faster. Your client may have purchased this type of rug at a low price and may not be willing to spend what it is worth to clean it.

It is possible to pull the knot tight and raise one warp yarn above the other. This is more frequently done with the Persian knot but can be done with Turkish knot as well. The result is a depressed warp. One node (half of the knot) is not visible from the back of the carpet. This allows greater detail in the pattern because the yarn ends are closer together. Finer curvilinear design can be created.

Another result of this “depressed warp” construction is that the foundation is thicker. There is greater space to hold soil. It takes more effort to remove soil in the dusting step. A vacuum cleaner with a beater bar often works to remove dry soils from a rug without depressed warps. However, special dusting equipment, extra effort or both will be required to do a good job of dusting rugs with depressed warps. Allow more time to remove gritty soil. Don’t take shortcuts.

How can you tell if a rug is constructed with depressed warps? Usually by looking carefully at the back of the rug. If the warp is not depressed, there will always be two nodes for every yarn. Colors will always appear two at a time or in even numbers. But with one node hidden, you will find some colors with just one node or an odd number of nodes as you look across a row on the back of a rug.

Single or double weft

Either one or two weft threads may be placed between each row of knots. When a single weft is used, it is usually a thinner, more flexible yarn. When two weft yarns are inserted after a row of knots, one of the weft yarns may be thicker and heavier.

When the weft yarn is heavier and less flexible than the warp yarns, the warp is forced to bend around the weft rather than vice-versa.  Segments of the warp threads yarn will then be visible on the back. Only a portion of the warp will be covered by the pile yarns. Look for alternating white thread on the back to help identify a single-wefted rug.

Heavier weft yarns in the foundation add stiffness and weight. Thus double (or sometimes triple wefts) will contribute to making a rug stiffer and giving it more body than a single, thin weft yarn.

Open fields

Some rugs have open fields, while others fill every inch with detailed design. An intricate design can help to hide soil and stains. This may mean the client is not as aware of stains and does not bring the rug in for cleaning as often as they should.

If some stains are not removed by the cleaning process, they will be readily apparent on a field of a single color.

Scott Warrington has more than 40 years of experience in the carpet cleaning industry and related fields. He serves as the technical support specialist for Bridgepoint Systems and Interlink Supply. He can be contacted at [email protected].


Cleanfax Staff

Cleanfax provides cleaning and restoration professionals with information designed to help them manage and grow their businesses.

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