To begin making a carpet, you need a foundation consisting of warps strong, thick threads of cotton, wool or silk which run the length of the carpet and wefts similar threads which pass under and over the warps from one side to the other.  The warps on either side of the carpet are normally combined into one or more cables of varying thickness that are overcast to form the selvedge.

Weaving normally begins by passing a number of wefts through the bottom warp to form a base to start from.  Loosely piled knots of dyed wool or silk are then tied around consecutive sets of adjacent warps to create the intricate patterns in the carpet.  As more rows are tied to the foundation, these knots become the pile of the carpet.  Between each row of knots, one or more shots of weft are passed to tightly pack down and secure the rows.

Depending on the fineness of the weave, the quality of the materials and the expertise of the weavers, the knot count of a hand made carpet can vary anywhere from 16 to 550 knots per square inch.

When the carpet is completed, the warp ends form the fringes that may be weft-faced, braided, tasseled, or secured in some other manner.

Looms

Looms do not vary greatly in essential details, but they do vary in size and sophistication.  The main technical requirement of the loom is to provide the correct tension and the means of dividing the warps into alternate sets of leaves.  A shedding device allows the weaver to pass wefts through crossed and uncrossed warps, instead of laboriously threading the weft in and out of the warps.

Horizontal Looms

The simplest form of loom is a horizontal; one that can be staked to the ground or supported by sidepieces on the ground.  The necessary tension can be obtained through the use of wedges.  This style of loom is ideal for nomadic people as it can be assembled or dismantled and is easily transportable. Carpets produced on horizontal looms are generally fairly small and the weave quality is inferior to those carpetss made on a professional standing loom.

Vertical looms are undoubtedly more comfortable to operate.  These are found more in city weavers and sedentary peoples because they are hard to dismantle and transport.  There is no limit to the length of the carpet that can be woven on a vertical loom and there is no restriction to its width.

There are three broad groups of vertical looms, all of which can be modified in a number of ways: the fixed village loom, the Tabriz or Bunyan loom, and the roller beam loom.

The fixed village loom is used mainly in Iran and consists of a fixed upper beam and a moveable lower or cloth beam which slots into two sidepieces.  The correct tension is created by driving wedges into the slots.  The weavers work on an adjustable plank which is raised as the work progresses.

The Tabriz loom, named after the city of Tabriz, is used in North Western Iran.  The warps are continuous and pass around behind the loom.  Tension is obtained with wedges.  The weavers sit on a fixed seat and when a portion of the carpet has been completed, the tension is released and the carpet is pulled down and rolled around the back of the loom.  This process continues until the carpet is completed, when the warps are severed and the carpet is taken off the loom.

The roller beam loom is a traditional Turkish village loom, but is also found in Iran and India.  It consists of two movable beams to which the warps are attached.  Both beams are fitted with ratchets or similar locking devices and completed work is rolled on to the lower beam.  It is possible to weave very long carpets by these means, and in some areas of Turkey carpets are woven in series.

In order to operate the loom, the weaver needs a number of essential tools: a knife for cutting the yarn as the knots are tied; a comb-like instrument for packing down the wefts; and a pair of shears for trimming the pile.  In Tabriz the knife is combined with a hook to tie the knots which lets the weavers produce very fine carpets, as their fingers alone are too thick to do the job.

A small steel comb is sometimes used to comb out the yarn after each row of knots is completed.  This both tightens the weave and clarifies the design.

A variety of instruments are used for packing the weft.  Some weaving areas in Iran known for producing very fine pieces use additional tools.  In Kerman, a saber like instrument is used horizontally inside the shed, and in Bidjar a heavy nail like tool is used.  Bidjar is also famous for their wet loom technique, which consists of wetting the warp, weft, and yarn with water throughout the weaving process to make the elements thinner and finer.  This allows for tighter weaving.  When the carpet is complete and dried, the wool and cotton expand to make the carpet incredibly dense and strong.

A number of different tools may be used to shear the wool depending on how the carpet is trimmed as the carpet progresses or when it is complete.  Often in Chinese carpets the yarn is trimmed after completion and the trimming is slanted where the color changes, giving an embossed three-dimensional effect.

Two basic knots are used in most Persian and Oriental carpets: the symmetrical Turkish or Ghiordes knot (used in Turkey, the Caucasus, East Turkmenistan, and some Turkish and Kurdish areas of Iran), and the asymmetrical Persian or Senneh knot (Iran, India, Turkey, Pakistan, China, and Egypt).

To make a Turkish knot, the yarn is passed between two adjacent warps, brought back under one, wrapped around both forming a collar, then pulled through the center so that both ends emerge between the warps.

The Persian knot is used for finer carpets.  The yarn is wrapped around only one warp, then passed behind the adjacent warp so that it divides the two ends of the yarn.  The Persian knot may open on the left or the right, and carpets woven with this knot are generally more accurate and symmetrical.

Other knots include the Spanish knot looped around single alternate warps so the ends are brought out on either side and the Jufti knot which is tied around four warps instead