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Synthetics dyes were accidentally discovered by William H. Perkin, an eighteen-year-old English chemistry student, in 1856, and were produced from coal tar. The first synthetic dyes were called aniline dyes. The Germans developed a type called azo dyes These early dyes were characterized by bleeding and fading of colors. But by the beginning of the 20^th century, a new group of chrome mordant synthetic dyes came into being which were not plagued by these problems.

With the rapid development of synthetic dyes and their acceptance throughout the world, they were being adopted by oriental rug weavers by as early as 1860's. By the beginning of the 20^th century synthetic dyes had almost totally displaced natural ones. Recently, the market has shown a renewed interest in the production of naturally dyed rugs.

Natural Dyes come from plants, minerals and insects. Some of the most common natural dye sources are:

• madder for a warm red and cochineal, derived from various species of scale insects, for a cool red
• saffron crocus stamens, pomegranate rind, dyers weed, larkspur, chamomile, salvia and certain sumacs as sources of yellow
• indigo for all shades of blue
• husks of walnut and oak trees for shades of brown

Greens resulted from combining indigo with a yellow dye. True greens in oriental rugs are scarce, but do exist. Many greens become blue green with time as the yellow component fades.

Orange resulted primarily from combining red and yellow dyes. Some orange red shades resulted from the use of weakened madder dye baths.

Many colors in violet/purple color range resulted from combining a red and indigo. Some are the result of a special treatment of madder.

The browns derived from walnut and oak husks, because of their tannic acid content, are corrosive, causing the fiber to become brittle and wear more quickly. In general, this is not considered a negative features because it results in an etched effect. Natural brown wool was also used.

Black was usually produced with combination of tannic dyes, such as oak acorn husks or pomegranate tree gals, with iron salts. As with brown dyes, black is corrosive, only more so.

Certain metallic salts of iron, aluminum, copper or tin, called mordants, were used attach natural dyes to wool fibers.

An important issue before anybody interested in oriental rugs is the question of how to distinguish between Natural and Synthetic dyes.

The only sure way to distinguish between natural and synthetic dyes is by laboratory analysis. However, one skill possessed by most experienced collectors is to judge this using colors, fading and bleeding. This method is often fallible.

One of the visual difference between natural and synthetic dyes is the way in which they penetrate the fiber. Natural dyes show subtle gradation of colors while synthetic dyes penetrates the fiber evenly.

With exposure to light and use, synthetic dyes fade while natural dyes become softer and mellower. To confirm the degree of fading, fold a rug to see the base of the knot. If a natural dye was used, the color will be usually uniform from the tip of the knot to the base. If, instead, is a  synthetic dye was used, it would not be so.