THE BEAUTY OF CARPETS also depends upon the quality of yarns that go into their construction. The warp consists of a set of parallel yarns held taut on a loom. The weft is composed of cross-wise yarns that interlace with the length-wise warp yarns as weaving progresses. The pile is formed by rows of what are called knots projecting from the foundation of interlacing warp and weft. Each knot is formed by inserting a supplementary yarn and wrapping it around a pair of warps. After weaving, the pile is cut to a uniform height.
Only the pile yarns are visible on the surface of a carpet. It is the pile that carries the colors, designs, and patterns. Thus, Oriental carpets are two-dimensional in the appearance of surface design; they are, however, three-dimensional in structure.
The type of knot used in the construction of a carpet is one of several technical characteristics which, when considered with style, provides a means of grouping Oriental rugs. Comparing rugs with similar technical and stylistic features may help in figuring out where they may have come from and who wove them.