Hi Doug
Below are a few examples of how to test for real silk,I know you will like the last one
I use the burn test,this supplies me with enough information to make a decision.
Rubbing the pile, is not accurate and you need another silk rug along side of you for comparison and being that not many of us are in the habit of carrying silk rugs on our vans as a normal every day activity :
then it's unlikely you could make a judgement on this alone.
(This information is supplied by Bukhara Rugs)
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.
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).
Dissolve it! :
The most accurate test is one that chemically differentiates protein from cellulose or petrochemicals. One such test: at room temperature, mix a solution of 16 g copper sulfate (CuSO4) in 150 cc of water. Add 8-10 g glycerine, then caustic soda (sodium hydroxide: NaOH) until a clear solution is obtained. This solution will dissolve a small sample of natural silk, but will leave cotton, rayon, and nylon unchanged.