Antique oriental rugs often display a characteristic that one never finds on rugs made after the invention of synthetic dyes. Antique oriental rugs frequently have abrash. Abrash is the name given to the hue or color change that can be observed when viewing older rugs from multiple angles. Abrash results from either inconsistent dyeing or the introduction of new wool before a given rug has been completed.

Scholars who study antique oriental rugs have long puzzled over how the ancient rug makers gave their products such deep, rich colors. Recently, two such scholars, Jack Haldane and Nest Rubio, have attempted to replicate the ancient dyeing process they envisage it. These studies have focused on the ability of yarn to absorb the red color from the natural madder root.

Haldane and Rubio reasoned that the makers of antique oriental rugs did not want to waste valuable fuel to heat the water that was used to dye the wool for the rugs. They reasoned that the absorption or the madder dyes must have taken place over an extended period of time, and at temperatures about equal to those used for making yogurt. The reasoning of Haldane and Rubio showed an excellent understanding of the mind-set of the ancient rug makers. They did not do things in a hurry.

The information gleaned from those studies underlines the simplicity of the process used to dye the wool for the antique oriental rugs. The wool would probably soak for up to 30 days in a mixture that resembled a water solution with 25% Alum. Then it would soak for 3 to 7 days in a mixture that was one part water and one part madder root. What resulted from all that soaking were antique oriental rugs with lovely pinks, vivid reds and striking deep Burgundies.