Next comes the matter of colours, that amazing artist's palette so typical of Persian carpet production. Dyeing is a very delicate process and is preceded by and alum bath which acts as a mordant. The thread is then immersed in a dye bath where it remains for a period ranging from a few hours to a few days according to the results required. Finally, it is put out to dry in the sun. Aniline was discovered in
1856, and its range of colours only reached Persia at the very end of the last century. Until the advent of these artificial colourants, dyers used nothing but natural ones, nearly all of them vegetable dyes. The exception to this among the most widely used colourants was the red obtained from the cochineal bug, an insect prevalent in India. Persian dyers become very famous over the centuries for their success In obtaining a seemingly inexhaustible range of colours from vegetable sources. Red, for example, was obtained not only from the cochineal bug but also from the root of the madder, a plant which grows wild in many parts of Persia. Other shades of red were obtained from other insects, while the pinkish-red and reddish-brown shades were the result of mixing whey with the normal red to produce a variety of shades of the same colour according to the amounts added.
Blue was obtained from the indigo plant, or more precisely, from the leaves of that plant. A very dark shade of blue, almost black, resulted from the use of the indigo which became encrusted on the inside of the fermentation vats. Yellow was obtained either from vine leaves or from a plant indigenous to the desert regions, or from weld which gives a beautiful saffron colour. Today, however, yellow obtained from weld is only rarely used, partly because it has become very expensive and partly because the more delicate tints are not perfectly fast. Green was obtained by mixing yellow and light blue which came from copper sulphate. Black came either from using the natural wool of black sheep or camels, or by dyeing grey wool with ferrous oxide found in the galls on oak trees.
Finally, the greys browns were derived either from the natural colour of the wool or from dyeing carried out with ingredients taken from walnut shells. The use of ferrous oxide had the inconvenience of weakening the pile. In several old carpets, one can see where the black areas have become very worn and this creates a curious relief effect. This defect can also be seen in the green areas because of the use of copper sulphate. The creation of the colours by means of natural dyes is therefore very dependent upon the competence and skill of the dyers. The type of mordant and the hardness of the water used also have their effect. The water at Tabriz, for example, gives a certain dullness to the dyed wool. When, however, between the last decade of the nineteenth century and the beginning of the twentieth century, artificial colourants (the whole range of aniline colours) made their appearance in Persia, dyers abandoned the old traditions in favour of the much less costly new colours. Quality suffered and for a long time the fame of Persian carpets declined also, because the aniline colours gave tints which did not match and moreover had a tendency to discolour. The government itself had to intervene to preserve the quality by imposing very severe penalties against the importing and use of aniline dyes.
Persian dyers have been able to profit from the later progress in the chemical field and today, while the nomads tend still to usc the natural colours exclusively for their dyes, town craftsmen and lagre workshops usc many synthetic chromebased colours which do not have the defects encountered in the aniline dyes. Chemistry also serves the creators of Persian carpets by providing the means of toning down the colours. This is called a reduction wash and is a chemical process which blends and softens the colours, making them more like the colours of antique carpets. It is a delicate operation which docs not affect the durability and strength of the carpet, and this is all the more reason for purchasing carpets of a particular kind from a source where the processes used have been perfected from all points of view.
Often one finds a Persian carpet which at first sight appears to have a defector a rare effect according to one's point of view-but which is, however, a characteristic peculiarity. Certain designs or backgrounds begun in one shade of colour are continued in the same colour but in a slightly different shade, or simply with another colour. These discrepancies in colour are called abrash.
Abrash are, in fact, those variations of colour or shade which are particularly to be found in antique carpets. The presence of abrash is proof that the carpet was dyed with vegetable colourants. Indeed, with vegetable dyes it is very difficult to achieve two identical shades of the same colour.
As was pointed out at the beginning of the chapter, hand-knotting is the essential characteristic of all Oriental carpets. The knots used arc of two different kinds: the Turkish or Ghiordes, and the Persian or Senneh.
The use of Turkish or Persian to distinguish the two different types of knot avoids confusion because these terms refer to the areas where the type of knot is mostly used. The Turkish knot is prevalent in Turkey and the Caucasus. The Persian knot is used mainly in Persia (although oddly enough, in the town of Senneh which gave its name to the Persian knot, it is the Turkish knot which is mainly used for carpet-making).
In the Turkish knot the yarn is taken twice around two adjacent warp threads and the ends are drawn out between these two threads. (see sketch on opposite page). In the Persian knot the wool thread forms a single turn a bout the wa rp thread. One end comes out over this thread and the other over the next warp thread. By parting the pile of the carpet, it is possible to sec a line of knots and determine whether Turkish or Persian knots were used.
With Turkish knots two ends come out on top of the knot, while in Persian knots one comes out at the top and the other is at the side.
As explained at the beginning of the chapter, the warp is the combination of threads stretched between the two extremities of the loom, around which the knots which form the pile are tied. Warp threads are usually of cotton. In nomad carpets the warp is of wood. The warp can be of silk in those rare carpets which arc made solely of this material. The fringes of the carpet arc the ends of the warp threads.
The weft is formed by the thread or group of threads situated between one line of knots and the next. The weft is of cotton, wool or silk according to the material used for the warp.
The function of the weft is to hold the knots in parallel lines and to strengthen the fabric of the carpet. In most carpets the weft consists of two threads, one loose and one tight, which are woven across the warp after each line of knots. The weft threads are beaten in against each row of knots with a comb beater.