Things You'll Need
Instructions
Visit rug conventions, dealer fairs and previews of sales at major auction houses like Sotheby's, Christie's or Skinner's. This gives you the opportunity to see and handle hundreds and eventually thousands of rugs. You will have opportunities to ask questions of people who have some expertise. Asking questions that showcase your own knowledge elicits better dialogue. Ask about patterns, for instance, and how they are arranged on the carpet. Ask what story the rug is telling, since many do just that. Collectors, dealers and auction house staff are usually generous with their time and knowledge.
Read as much as you can about historical rugs and carpets. People like George O'Bannon spent years cultivating his knowledge of rug quality and origins. O'Bannon traveled extensively while in the Peace Corps, and had opportunity to view thousands of carpets during this time. He also amassed a large collection of his own. His articles can be read in "Oriental Rug Review" and he has authored several books on the subject. Another excellent source of information about insect dyes was penned by expert Paul Mushak. Mushak performs dye testing on fabric as a business and lives in North Carolina.
Scrutinize actual rugs rather than pictures of rugs. Color reproduction is too imprecise to be advantageous, so only eyeballing the real thing will give you that expert eye. Some rules for beginners have to do with the history and characteristics of certain colors.
Blue or indigo dye is the same chemical whether natural or synthetic. An interesting property is that it only coats the surface of a yarn. This is the cause of blue jeans "fading" -- they don't actually fade, but the high areas abrade off, causing the white cotton yarn to show through.
Natural green dyes are rare. Early Turkoman pieces have a natural dark green dye, but most greens seen on rugs prior to the availability of synthetic dyes are produced by dying with indigo and natural yellow consecutively. Some natural yellows are sensitive to light, so the exposed surface color will be indigo while the back or inner pile will reveal the original green color. Another way to tell if the dye used for green is synthetic, and therefore more recent, is that the color remains true without fading or abrading off at the tips.
Contemplate the facts. Colors such as black and brown were sometimes not dyed at all but the natural color of the sheep the wool came from. When dyes were used for these dark colors, their properties caused corrosion of the wool and older rugs have much wear from this. Short or absent pile where these colors were used are evidence of age. Be warned, however, that consistently short black or brown pile throughout a carpet can mean only that the weaver has cut the yarn shorter in an effort to fool a buyer.
Natural purple dyes are uncommon and synthetic purples are sensitive to light. Pushing back the pile will reveal this sign of fading.
Red is a color impossible to tell natural from synthetic without chemical tests. Even the most educated eye can be fooled by red dyes. Look to other colors in the carpet for dating clues.
Oranges and yellow are also not good eyeballing colors.
Generally, rugs with a number of vivid colors that have faded tips (which can be noted by spreading the pile and looking at the bases of the knots) are usually Persian or Caucasian made between World Wars I and II.