The wool of the sheep is shorn by hand, then washed in a particular manner to take off dirt and fat. After drying and classifying, it is carded and then spun. In recent years several washing, dyeing and spinning machines suitable to Persian carpet weaving techniques, have been introduced.
The wool is treated with vegetable and animal dyeing material. In each district there exist special methods and formulas for dyeing the wool. After dyeing, the wool is washed in clear water and hanged to dry. Vegetable dyes are obtained from madder- root, walnut peels, grape leaves, esparak (spurge) straw, dyers, weed, pomegranate peels and gall nut. Animal dyes come from cochineal, acidulated milk, qaraguroot, etc. Minerals and chemicals are also used in conjunction with the dyeing formula such as caustic soda, citric acid, hydrosulphide and alum. These chemicals are required to make the dye fast and prevent the colors from washing away.
The designer draws the pattern on pieces of paper pasted side by side to make one quarter of the area of the carpet. The design is colored and handed over to the operator who places it before him in front of the loom and uses such wool in his weaving that matches exactly with the colors in the drawing. Two methods are used in weaving Persian carpets: the Turkish and the Farsi (Persian) knots. In the Turkish method knots are tied with the help of a hooked needle. The Farsi method uses no needle; knots are tied entirely by hand.
The carpets of the Turkish method are more durable in texture because of the system of knots in the warp, but the texture on the back of the carpet does not look as even as that of the carpets of the Farsi method. The Farsi carpet, due to the different method of knots tied in the warp, has an even and nice-looking back. The back of these carpets looks fine and smooth, though the number of knots made in every square inch may be the same as thatintheTurkish method. The loom of classic rugs, namely the ones made in towns are erected vertically and stand in front of the operator, while the looms of tribal rugs such as Baluch and Turkman are set horizontally. The looms of the tribal rugs are smaller compared to with those used in other areas, which are more classic in structure. A loom is basically a frame of wood on which the warp threads are stretched tightly between the upper and lower crossbeams. The warp consists of threads lying close together (the finer the carpet the closer and thinner the threads) and running the length of the loom. Onto these warp threads is knotted the woolen yarn which forms the pile of the rug. When one row of knots is completed across the width of the carpet, a weft thread (of cotton mainly) is inserted down against the knots as firmly as possible to give the knots and the fabric strength and firmness. The process is repeated row after row until the pile of the carpet is completed. Then follows the last part of the operation, namely the shearing of the pile which has to be trimmed to the desired length for a thick mass of woolen threads is still hanging on the front. The tighter and closer a pile is knotted, the shorter it can be cut. Close knotting has the advantage that the outline of the design shows clearly and is not hazy. It has the precision of a painting. But loose and coarse knotting gives indistinct and vague contours. The knotting must be even and regular for the design to show clearly. If one looks at the back of a well-knotted carpet the designs and colors stand out clearly and the more exact and sharply defined this pattern appears the better the carpet has been worked. In the machine-woven carpets, the pattern appears only very hazily. This is a sure sign that it has not been hand knotted.