One of the most important visual factors of carpet is color. Generally, chromogenic substances can be categorized as follows :
1-     Pigments :
These are soluble in organic solvents and are not used in dyeing.
 
2-     Chromatins (bases) : 
Chromatic substances absorbed by materials either via the absorbtion phenomenon or through diffusion (penetration). They are soluble in water and are divided into two natural and chemical types. 
 
-    Chemical chromatins are divided into two classes :
1-     Aniline dyestuffs :
They lack appropriate stability to washing, alkali and sunshine.
2-     Chromium dyestuffs :
Due to their dentate substances, these dyestuffs are suitably stable.
-   Natural chromatins are categorized into three classes :
1-     Vegetal : 
Amongst these dyestuffs, madder (alizarine), dyer’s weed (Reseda luteola), pomegranate skin … can be mentioned.
2-     Animal : 
Cochineal (carmine) and also dried louce skin are included in this class.

 
3-     Mineral :
These natural dyestuffs are not used in dyeing [carpet yarn].Amongst the natural chromatins, the vegetal dyestuffs are the most important and the most common ones which in turn are divided into two tannin containing and tannin-free types.
 
-   Natural tannin-containing chromatins (dyestuffs):

These chromatins contain stabilizing materials (tannins) and without using dentate they are easily absorbed by the stuffs to be dyed. Amongst the most important of such chromatins, pomegranate skin (cortex), walnut cortex, sumac, oak … can be mentioned.

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-  Natural vegetal tannin-free chromatins : 
These chromatins have no affinity to be absorbed by the fiber and to increase stbility of color using such chromatins, use of dentate is compulsory. The most important of such chromatins are : dyer’s madder, dyer’s weld (Reseda luteola), woad (indigo) leaves, sofflower etc.
 
From the category of natural chromatins we will explain some of them :

Madder (Rubia tinctorum)

This is a perennial weed which grows in all parts of Iran. Using this plant and different dentates, various tonalities of red color of excellent stability are obtained. Dyeing power of madder lacquer is more than the plant itself.

 
Dyer’s weld (Reseda luteola) :

This is a wild plant which is seen in all parts of Iran. Using this plant, and employing different dentates, various tonalities of yellow color with good stability can be obtained.

Walnut cortex :

Walnut is a beautiful monoecious tree that the cortex of its fruit is used in dyeing which via different dentate provides various tonalities of brown hue.

 
Pomegranate cortex :

Pomegranate (Punica granatum) is a very beautiful shrub with fiery red rose flowers that its long period of flowering adds to its charm. It grows on coasts of the northern sea and steppe regions and from its leathery pericarp, via different dentate, various hues of cream-brown color can be obtained.

 

 
Indigo (Indigotera spp) :

This is a shrub, the dried leaves of which provide an indigo dyestuff used in dyeing and it is the origin of all blue hues from sky blue to turquoise, azure (cobalt-blue) and dark blue which are very stable against light (sunshine).

 
Cochineal :

This is the most important animal dyestuff. Morphologically it resembles a compacted pea. From this insect, different hues of red color are obtained.

 

 
Contrary to artificial dyes which are translucent, natural dyes seem dark and opaque and under the gradual effect of light, abraison and washing, they loose their crudeness and gain a mild lusture and a pleasing ripeness. Generally,, in carpet yarn dyeing, employing proficiencies and ancients’ masteries, beautiful and peerless colors are presented and even today in spite of import of chemical dyestuffs to the country,, dyeing with natural dyestuffs is still considered as an unseparable element of the general structure and composition of the Persian carpet.
 
 
Dyeing Procedure

Since ancient times, in most of the cities and villages of Iran, dyeing has been done via traditional procedures using such tools and instruments as cauldron, pad … and occasionally by mechanical semi-automatic machines and in workshops by professional dyers or in the houses by skilled weavers. Today in some parts of the country factories have been established in which dyers, using natural dyestuffs and according to the ancient dyeing guidelines but in precise and controlled conditions, employing modern technology and mechanical and automatic machines are dyeing; perhaps it could be mentioned as an industrial procedure.

traditional dyeing

Color Stability

 Based on Persian carpet standards : The hand-woven carpet from the viewpoints of resistance to light (sunshine), water, water solvents and friction should have the color stability No.  27. For each of the above said factors grading is as follows :

  Grade of color stability to light

5

  Grade of color stability to water (blotching)

4

  Grade of color stability to water (color change) 3
  Grade of color stability to organic solvents (blotching) 4
  Grade of color stability to organic solvents (color change) 4
  Grade of color stability to friction (color change) 4
  Grade of color stability to friction (blotching)  3
  Total 27