The height of the pile depends on the pattern and on the wishes of the buyer. In many old pieces and in the luxury carpets of the court manufactories it is especially short, so as to show off the delicacy of the design to the best advantage. Right into the twentieth century the saying holds: ‘The thinner his carpet, the richer the Persian.’ The Persian custom of exchanging the thin ‘summer carpet’ for a thicker one in the cold season or of covering it with a felt carpet (nomad) is no more current now than the gathering of the family round the charcoal brazier (mangal) under the gigantic round padded coverlet (lahaf).

The nomad carpet, especially in the mountain regions, fulfils its function of insulation against the cold better if its pile is long – no matter if the outlines of the pattern is blurred. Some very thin nomad pieces are made, however, in western Turkestan.

Two principal kinds of knotting are used:

a) The Turkish (Ghiordes) knot. The region of its use includes a number of areas besides Turkey.

b) The Senneh (Sehna,Sanandaj) or Persian knot. In the region of Sehna, modern Sanandaj, however, nearly all the carpets are done with Turkish knots. On the other hand the Persian knot is used over most of Persia, western Turkestan, India and China, and in Sparta (Isparta) in Turkey.

Both methods have their advantages and disadvantages: the Turkish knot is firmer. The Persian knot enables fine contours to be kept more flowing, because the ends do not come up together. But if the warp is on two levels, one series of threads lying obliquely or vertically above the other, then the ends of the pile are pressed so close together out of the ground weave that very delicate designs can be achieved with either method.

Other methods of knotting, such as that round only one warp thread (see below) are confined to Spain or were only used sporadically in the East. We mention two in passing: Chufti, which knots round four warp threads, so that the knot loops round two pairs instead of two threads, and a nomadic use of Turkish knots for their ornamental bands over three warp threads.

Bidjar is not a different kind of knotting but uses an extremely thick, sometimes moist weft thread (argach) between strongly depressed warp threads. The second, thin, weft thread (pud) then runs in and out of every warp thread in a very sinuous movement. Bidjar in a very refined form is found in most carpets from the old established centers (Sivas, Tabriz, Saruk, Kashan, Kirman, Isfahan).

Towel or terry weave and single loop techniques are both important in she history of the development of the Middle Eastern carpet.

In the Egyptian carpets of the Roman period executed in towel or terry weave the warp, weft and white pile loops all consist of right spun linen. Right spun wool was used for all the colored pile loops. Warp: linen S-spun single ply, undyed up to 8o warp threads per dm. Weft: linen S-spun single ply, uncolored. Three wefts alternating straight, so tight that they remain almost invisible. Pile loops: wool S-spun, two strands untwisted, colored, and linen S-spun untwisted, uncolored light. The pattern thread was carried in front across five warp threads, then brought back to the right in the shed between three front and three hinder warp threads leaving a loop about 1 cm. long above the ground weave. Then the free end of the pattern thread was led on over five warp threads to begin the next loop. Density: up to ten rows of loops in one vertical dm.

The Egyptian single-loop technique reserves linen as the material for the ground weave. The loops forming the pattern are always of wool except the white loops, for which linen or cotton was used. Warp: linen, Z-plied, two strands twisted, undyed light. Weft: linen S-spun, five to seven strands, untwisted – one Z-plied, two strands slightly twisted – undyed light. The five, six or seven strands of weft, each of three strands left-plied, were straight. Pile: wool S-spun, single, or else cotton or linen for white loops. Single loops round every other warp thread lifted by Hamadan weave, and alternating with the next row. The loops are hardly visible on the back. Density: up to about 2,700 loops per square dm. Although only every other warp thread takes a loop the horizontal density is always greater than the vertical because of the thick weft threads.

A technique used only sporadically and rarely in south Persia and Tabriz binds in a third warp thread on the back of the carpet at every other weft (so that these pieces seem to be overlaid by a close mat of vertical threads). It no more needs a special knot than the very rare ‘two-faced’ reversible carpet, which shows the pile on both sides because every other row of knots is put in on the underside.

As can be seen from the drawings, the knot is not literally tied; it is rather wrapped around the warp threads. It is made firm simply by pressing the weft close against it. The ends of the yarn in the Turkish knot come up together between the warp threads and incline slightly towards the starting end of the carpet. This produces the lie or set of the pile. The ends of the Persian knot are separate, since the knot only wraps round one warp thread completely and does not come round the front of the second. Depending on whether this second warp thread is the left- or right-hand one of the pair, the pile inclines downwards to the left or right. Senna knots are termed either right-handed (S Ib, S III) or left handed (S la, S II). The right-handed knot (S Ib, S III, T III) is rarer because the knife has to be held in the left hand and is thus more suitable for left-handed people.

To ascertain the kind of knotting, the carpet is folded back parallel to a line of the weft. If the horizontal part of the knotting yarn covers both warp threads and its ends appear together, it is a Turkish knot. lf the warp thread can be seen between the two ends of the knot it is a Persian knot. If the knot is moistened it makes it easier to see. It is difficult if the knotting is very close and the warps are on two levels, and if it is not wished to sacrifice one of the knots then the only way is to examine the first or last row of knots from the side. Even then there is room for error because sometimes Persian knotted carpets have the end rows in Turkish knots to make them firmer. For this reason a carpet must be examined at several different places to make sure.

If the warp threads lie side by side at the same level in the knot (T I, P la, P Ib) it appears on the back of the carpet as two humps, identical in the Turkish knot and almost identical in the Persian. If the knot count and thus the density is to be increased for the same breadth, the warp threads instead of lying side by side are held one above the other, depressed or on two levels ( T II, T III, P II, P III). For this the first weft thread instead of running sinuously in an undulation, in and out of the warp threads, alternating with the return thread (P la, P Ib, T I), runs straight between them. The warp is depressed, or on two levels. On the back the second hump of each knot appears in a vertical groove.

The depression of the warp can be as much as ninety degrees: in this extreme case the two warp threads of each pair lie directly one above the other; on the back only one hump is visible. The knotting is now twice as dense across the breadth as with the warp on one level. The density of the knots along the length is unaffected by the depression and depends on the thickness of the knotting yarn, the thickness and number of the weft threads and on how hard and close they are beaten together.

A special weft weave was used predominantly in the region of Hamadan and in other areas of (especially west) Iran. As in haute lisse only a single thick weft thread is pulled through straight, so that every other warp thread is exposed at the back while its neighbor disappears behind the weft. In the weft row following the next row of knots the weft raises the warp threads which it had pressed down in the previous row. The most usual term for this procedure is Hamadan.

The density of the knots, the count or gauge, is expressed in the number of knots per square decimeter. It can range from less than a hundred to 8,ooo in wool carpets, and in silk carpets it may be as many as 15,000 or even much more in special cases. It is reckoned by multiplying the number of knots in a square of ten centimeters along the length by ten centimeters across. To make the count a square of ten centimeters is measured or marked off on the back. Having made sure that there is no ninety-degree depression by examining a place in the pattern which is only one knot thick, the humps on the bade are counted. Lengthways one hump is always one knot, but crossways this is only so if there is a ninety-degree depression, otherwise there are always two humps to a knot. It is more convenient to count the humps along a card ten centimeters long or, even simpler, to read them off in either direction on a thread counter with an aperture 2.5 X 2.5 cms. and multiply each result by four before multiplying them together.

Normally there is a higher knot count lengthways, but when the weft is thick, the warp threads thin and strongly depressed, it may be higher horizontally than vertically.

The following grading is recommended to describe density or gauge of a carpet:

up to c. 5oo knots per sq. dm. very coarse

from c. 5oo to 9oo knots per sq. dm. coarse

from c.9oo to 1,8oo knots per sq. dm. medium fine

from c. 1,8oo to 2,5oo knots per sq. dm. fine

from c. 2,5oo to 4,5oo knots per sq. dm. very fine

over 45,ooo knots per sq. dm. exceptionally fine

In Persia the count is expressed according to the number of knots on a gireh – exactly seven centimeters of the warp – e.g. 3o Regh = 3o knots to the gireh = 45 to the sq. dm.

For a very dense structure the weft yarn may be so fine and the beating so strong that the weft is almost invisible on the back. The details of the design are then more clearly seen on the back than in the pile. On the other hand the pattern of very coarse carpets is often unrecognizable on the back because of loose knotting and thick weft rows.

Besides knotted pieces (pile weaves) there are in the East textiles with separate parts of the pattern knotted in and carpets and blankets without pile. The brocaded carpets theoretically belong in the category of textiles with patches of knotting (nimbaf = half knots, golbaryasteh = rising flowers. These were made in Turkey, Persia (Polish carpets), India and East Turkestan with metal threads (thin gold or silver leaf wrapped round silk) woven into the areas between the knotted designs

Weaving was highly developed in the East long before knotting and reached its zenith in the fine brocades.