Assembling the loom: After the yarns are prepared and dyed, a loom is assembled for weaving. Looms used for pile rugs are not complex; they are basically rectangular wooden frames that are laid flat on the ground or propped into a vertical position. Their main function is to hold the lengthwise warp threads, keeping them taut, parallel, and in the proper order. The warp threads, made of cotton, silk, or wool, are stretched over the top of the loom and back again, to the full width of the loom or desired width of the carpet.

Sitting in front of the loom, the weaver inserts a shed stick through the warp yarns. The shed stick is thin, flat, and wide; it is passed over the first warp thread, under the second warp thread, over the third thread, and so on across the width of the warp. By turning this stick on its side, the weaver raises every other warp thread, creating a “shed” through which the crosswise weft yarns are passed, or “shot.” The heddle stick creates an alternate shed. Loops of string attach threads to this stick.

Weaving the foundation: The weft yarn, usually cotton or wool, is wrapped around a shuttle, a wooden implement that can pass easily through the sheds. Still seated in front of the loom, the weavers alternate the shed and heddle sticks to create two sheds through which the weft, the crosswise yarns, are passed. To begin a rug, several rows of weft are woven along its bottom edge.

Knotting the pile: The design of the carpet is carried in the knots, or pile. Following a cartoon or to-size drawing provided by a master designer or manuscript illustrator, several weavers might work on a rug at the same time. Knots are tied individually, by hand, around two warp threads. The most commonly used knot was the Senneh, or Persian knot. Depending on whether this knot opens to the right or to the left, the pile leans slightly in that direction.

After a row of knots is tied, a few rows of weft are added to stablize the row, then another row of knots is tied. The weaver uses a heavy comb or beater to pack the knots and weft tightly into the warp. Finally, the loose ends of the knots are clipped to create the dense pile surface.

Knots per square inch: The fineness or coarseness of the weave is determined by the number of knots tied per square inch, and this is figured from the back of the carpet, where the individual knots are easier to isolate and count. A square inch is measured off, and the number of knots going across the section is multiplied times the number of knots going down the section. Rugs made with thick yarns or with more shots of weft between the knot rows can have as few as 60 knots per square inch, but very fine rugs, woven with thinner yarns, can contain as many as 2,000 knots per square inch. These carpets look like fine velvet, and they can take years to produce.

The number of knots per square inch affects not only the time taken to weave the rug but also the sophistication of the design. Curved elements seem more curved, and subtle highlights and shadings can be achieved.

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