From JACOBSEN Rugs
Real SilkWe don't mean to be alarmist, but we sometimes see "silk" Oriental rugs that are made of something other than genuine, natural silk. This is not a problem if you know that the rug you are considering is made of artificial silk, but sometimes rug dealers neglect to pass on this information! The problem happens most often with just a few rug types sold in tourist markets in Turkey and India (and sometimes in Pakistan).
Real silk is produced as the cocoon covering of the silkworm, the pupal form of the Asian or mulberry silk moth, bombyx mori. The cocoon is spun by the silk moth caterpillar of a single silk fiber that can be up to several thousand feet in length. To harvest the silk, completed cocoons are boiled or heated to kill the silkworms, then laboriously unwound into single fibers which are plied together and spun into thread or silk yarn.Silk is extremely high in tensile strength, exceeding that of nylon. It has been estimated that if a single silk fiber with the diameter of a pencil could be produced, the fiber could lift a 747 aircraft (who figures these things out, anyway?). Silk is used to make Oriental rugs because dyed silk is a fiber with rich, saturated colors, and a distinctive, almost translucent luster.
Mercerized cottonCotton fiber is mercerized by being stretched under controlled tension at room temperature while being treated with a 21%-23% solution of caustic soda (NaOH). The effect is to swell the fiber and make its surface much more reflective, thus dramatically increasing its luster (and also its tensile strength). After the chemical treatment, cotton yarn is often singed to remove whatever small amount of fuzz remains on the surface of the fibers. Sometimes cotton is calendered by being passed between heated rollers. The effect is to increase the luster and sheen of the fiber still more.
RayonLike cotton, rayon is made of almost pure celulose, but rather than being grown, rayon is produced by first dissolving cellulose (obtained from cotton or woodpulp) to produce a thick yellow liquid called viscose. The viscose is extruded through tiny holes into a chemical bath that produces long filaments which can be spun into thread and yarn.
How to Identify A Real Silk Oriental Rug
With all these artificial fibers around, how can you identify a rug woven with natural silk?
First of all, pay attention to whatever clues the dealer--or the rug--gives you. For instance, we have seen many artificial silk Kayseri rugs (and some Hereke rugs), both Turkish types. In Turkey, a real silk Kayseri is an ipek Kayseri: ipek is "silk" in Turkish. An artificial silk Kayseri is a flos Kayseri ( a yun Kayseri has a wool pile). The dealer might be accurately describing the piece to you as a flos rug, but by not explaining the difference between flos and ipek, he lets you jump to the intended assumption, and you unwittingly buy an artificial silk rug.
Indian rug dealers are seldom as delicately circumspect as some of their Turkish counterparts. Artificial silk rugs in India are often blatantly sold as real silk, complete with certificates of authenticity and written guarantees.
Tests for Silk
OK, you're looking at a nicely woven, nicely patterned, closely clipped "silk" rug with what appears to be real silk fringe. You still might be looking at a rug made of artificial silk. Here are three field tests that might help you distinguish real from fake. No guarantee; your mileage may vary.
Rub it! It is sometimes claimed that you can tell real silk from artificial silk by vigorously rubbing the pile with your open palm. The real silk rug feels warm, the artificial silk rug stays cool to the touch. We sometimes think we have felt this difference. Of course, it helps to have a real silk rug with you so that you can compare a known quantity!
Burn it! This test is at least good theatre, and actually can be helpful. Clip off a small piece of the fringe, or pull a knot out of the rug from the back (why should the owner object?). Burn it. Look at the ash and smell the smoke. If the material was cellulose (rayon), the ash should be soft and chalky, and the smell should be like burning paper (most paper is made of cellulose). If the sample is real silk, the burning sample should ball to a black, crispy ash, and the smell should be of burning hair (you're burning protein, the same stuff your hair is made of). You've got to be a little careful with this test to avoid smelling the smoke from the match (and to avoid igniting yourself or the rug dealer's shop).