Types of Rug Dyes

Whether the rug manufacturer used synthetic dyes or natural dyes to make the rug might be a subtle difference, but one worth noting. Below is an excerpt from Rug News in which Peter Davies helps to clarify the difference between synthetic and natural dyes.

"Under an electron microscope, a wool fiber dyed with natural dyes has more of a speckled rather than a solidly colored appearance. As a result of these microscopic differences, the human eye perceives the natural dyed yarn as soft and muted. Conversely, the eye perceives wool dyed by synthetics as harsher, more aggressive, more extroverted in character…

“Not only do natural and synthetic dyes take differently to wool, but there are also important differences in the way natural and synthetic dyes are perceived by the human eye and brain. If, for instance three strands of wool are each synthetically dyed red, blue and yellow and placed side-by-side, the effect of the combination will be disharmonious. Whereas if three strands dyed indigo blue, madder red, and milkweed yellow are similarly placed, the effect will be quite harmonious. It is precisely because natural dyes are impure, and therefore reflect a broad range of wavelengths, that harmonious combinations are more possible. It is the overlapping of the hues that make for color harmony..."

Natural Dye

Natural dyes are derived from plant materials and insects such as indigo, madder, oak, sumac, pomegranate, cochineal and larkspur. Before the 1870s, they were the only source used to dye wool. Since the invention of synthetic dyes, there has been much debate about which type of dye produces a more beautiful and investment-worthy rug. Natural dyes tend to gently fade with time and therefore produce a sought after patina.

Aniline Dye

Aniline dyes are very acidic and tend to corrode the fibers in a rug. This type of dye was developed in 1856 and is no longer used.

Acid Dye

Acid dyes are cheap to make, but the colors run.

Chrome Dyes

In the 1920s and 1930s, chrome dyes became a more reliable alternative to aniline. These synthetic dyes are more steadfast and have a much wider spectrum of colors to choose from. Chrome dyes bind to the wool with potassium bicarbonate, which resists fading and does not weaken the wool. There are more than 600 chrome colors to choose from.

The Rug Dyeing Process

The dye used to create a desired color is very specific. A rug factory has a "dye specialist" who consults a book for the exact color formulas and ingredients. A rug dye is not an item that can be bought at a store and poured into a vat. Multiple colors must be combined at a specific temperature, and the yarn must remain in that dye for a specific duration. If the water is not the right temperature, or the yarn is not submerged for the right amount of time, then the entire batch could be deemed useless. The specialist must also take into account the effect that the weaving will have on the dye. Unspun yarn has a deeper, richer color than yarn that has been woven into a rug.