Oriental Rug Dyes
Three types of dyes have been used in the dyeing of Oriental rugs: natural (vegetable or animal), aniline, and chrome. Aniline and chrome dyes are synthetic dyes.
Natural Dyes Vegetable and Animal
Making and using natural dyes is tedious and time-consuming and can be quite expensive. The colors are derived from a number of different sources depending on what is available to the dyers. When local abundance of a natural source makes it economically feasible, vegetable or animal dyes are still used. These sources vary from country to country. The most common of the natural sources:
madder redroot of the madder plant; safflower
cochineal redcochineal incect, Indian lac
In older rugs there often appears a slight change of color which will run horizontally through the field of the carpet. This is called an abrash. This occurs when the weaver begins using yarn from a different dye lot than that previously used. With natural dyes, it is quite difficult to obtain an exact color match. This is not objectionable in itself and does not affect the value of the rug.
The use of aniline dyes was introduced to the carpet industry in the latter half of the nineteenth century. Being easier and cheaper to use, these dyes were all too readily adopted. They were strongly acidic, which destroyed the natural oil in the wool, thus weakening the pile and causing it to wear rapidly. The colors not only faded when exposed to sunlight, but ran when washed. The use of these dyes was not limited to one area but spread throughout the rug-weaving world. Aniline dyes are not as widely used as they once were; their use is generally limited to inferior-quality rugs. In older rugs aniline dye can easily be recognized by the faded color of the pile; the back of the carpet will be much brighter than the sunlight-faded front. To check for aniline dye in new rugs, rub a damp cloth over the pile. A good-quality vegetable or chemical dye will not rub off onto the cloth. If a color does appear on the cloth, an aniline (or other inferior) dye has been used and the rug should not be purchased.
The majority of rugs are now dyed with what are commonly referred to as "chrome dyes." These are synthetic dyes which have been treated with potassium bichromate. In contrast to the natural dyes, chrome dyes are much cheaper to use, simpler to prepare, and their dye lots easier to match. These dyes provide a wider range of shades and colors and are colorfast; they will not fade when exposed to sunlight, or washed with water or an alkaline solution. The natural oils of the wool are not removed by the dyes, so the wearing qualities of the rug are not impaired.
The major complaint about the early chrome dyes was that their colors were harsher than the hues of the natural dyes. This problem was corrected by the use of a light chemical wash.
Most rugs are given a light chemical wash before being exported. This wash simply enhances the richness of the rug and does not affect its durability. A luster, or sheen, may be given a carpet by the chemical wash. Several factors affect the amount of luster imparted: the type of wool used for the pile and the chemical concentration of the wash. Wools vary from region to region; certain wools are more receptive to the chemical wash, gaining a more lustrous appearance than others.
An "antique" wash has been developed to give new rugs an old look. This is a rather heavy chemical wash which tones down the colors and gives the impression of being an antique rug. Rugs with an "antique" wash can be detected by splitting the pile and examining its base. The top of the pile will have a drabber, muter color than the base. The wash also gives the fringes a brownish cast.