Look at the back of the rug.
Does it have a fabric or rubber backing? If you can’t see the knots, then it’s likely you are looking at a machine-made rug. Quality hand-knotted rugs will not have any kind of backing to hide the knots but instead the exposed knotting will reveal a vibrant outline of the rug’s design.
Look at the rug colors.
Is the rug completely and evenly faded? If the colors on both the front and back of a rug look bleached, they probably are. Vintage and antique rugs are sometimes treated with chemicals to achieve an “antique” look. Rugs naturally bleached by the sun will still be colorful on the back. The vegetable dyes of a quality vintage or antique rug should be colorful like gemstones or gently muted. Chemically treated rugs will make the rug fibers brittle and weak, which is disrespectful to the rug makers who spend over a year carefully handcrafting a rug meant to last generations.
Look at the pattern.
Does the rug’s pattern appear striped with white streaks? If so, it’s likely to be artificially dyed and possibly even machine made. Authentic vintage and antique rugs will often feature “arbrush” which is streaks of a different shade of color due to a different dye lot. Many lesser rugs try to imitate the look of an antique rug by artificially creating white streaks. Arbrush in authentic vintage and antique rugs will almost never be white. The natural irregularities in an authentic hand-knotted rug adds to its value.
Look at the pile of the rug.
Well-crafted traditional vintage and antique Persian rugs are carefully sheared after they are woven to reduce the pile and better highlight the intricacy of the design motifs. New rugs in the Persian style made in India use different wool and knotting technique. They will have a thicker pile and are not as tightly woven so the motifs in the design are not as crisp.
Look for imperfections.
Authentic vintage and antique rugs are imperfect by design. Look at the knots on the back of a rug. There will likely be an occasional random large knot among even the finest rugs. The knots should not be exactly alike and uniform everywhere. Do the rug’s edges curve a bit and/or sometimes feature double stitching? It is purposely imperfect. The aim of authentic rug weavers is to incorporate and accept imperfections. These one-of-a-kind qualities make hand-knotted rugs more desirable and valuable.