Dyes
Thanks to dye identification, it is sometimes possible to know when and where a carpet was made. For example, madder and indigo do not provide any information like this because they have been used for centuries in many parts of the world. Yellows do not help either because they are often too faded.
On the other hand, insect dyes do help with this. For example, lac, from India, was used in Egypt and Persia until the Spanish brought cochineal from Central America to Europe (where kermes was being used). Cochineal took over the marked due to its low cost in Europe (1550), Egypt (1600), and Persia (1800). By identifying the way a carpet was dyed, it is possible to give a rough estimate of the age of certain carpets. There are many other dates and figures that help in finding what dye was used where. Send us a message if you have further questions. Below are diferent dye techniques, their strengths, and weaknesses.
Vat Dyes
Insoluble pigment dissolved in alkaline vat by chemical reduction – for example fermentation. Fiber is soaked in vat then exposed to air. Through re-oxidation dye turns to desired color and is fixed to fiber.
Blue: Traditionally from indigo plant (shrub known in the Far East) but also synthetically since 1890. There is also woad grown in Europe, but it is more subtle.
Mordant Dyes
Acidic compounds fixed on fiber with ‘mordant’ (metal hydroxide – usually from an iron salt or solution of alum), in which yarn is soaked. Colors are affected by the mordant. Madder, which may be red / orange-red with aluminum, blue-violet with iron, and anything in-between when the two are mixed. These types of dye can be easily decomposed by acids, even ones present in wine or fruit juice. Bicarbonate of soda must be applied before washing to neutralize the acid and restore the color. Washing alone will take away both the mordant and the dye. Surprisingly enough, urine is much less harmful – it can simply be washed away. More harmful to mordant dyes is light: it decomposes mordant dyes, which is why museums tend to keep their carpets in dim-light. In any case, no carpet should be placed in direct sunlight.
Reds: Obtained from madder (roots of plant), cochineal and lac (insect dyes). Certain mollusks are also used to obtain red and royal purple. Various woods from Central and South America.
Yellows: Obtained from weld, curcuma, safron, residues from food crops.
Black: Obtained with tannins, derived from oak galls, and iron. Note: the combination of these two makes the fiber sensitive to light and corrodes it, which causes early aging in the black areas of some rugs.
Direct dyes
Synthetic dyes that work only on protein fibers of silk and wool. Fabric is dipped into the dyebath, then excess dye is washed out.
Aniline dyes are known as ‘basic direct dyes’ – applied to fabric in alkaline solution. Invented in 1858 was a brilliant magenta dye called fuschine. Then came violet, blue, and green of the same structure. All of these fade easily in light and around alkalis like washing soda and some soaps. Anilines do not bleed, but acidic dyes – the second group of direct dyes – have a tendency to do so.
The first acidic dye was indigo. Made with ‘extract of indigo’ (disulphic acid) obtained from a mix of indigo and concentrated sulphuric acid. Makes for a greenish-blue, often combined with yellow to make green. These dyes fade and bleed easily.
The most important acid direct dyes are azo-dyes, which were introduced between 1875 to 1890 with colors like yellow, orange, red, or violet-red. Some of them like Congo Red can be used for more than protein fibers, for cotton and linen. They are resistant to light, acids, and alkalis, but some do run, but it mainly varies depending on the skill of the dyer and the color being used.