Carding method and the equipments for this process, have undeniable effect on quality of the carpet. When carding of the wool was not utterly performed and its alien materials was not exhausted, the cords might stick together and the yarn would become uneven while spinning, therefore the carpet becomes uneven and sinuous. Many workshops still, utilize beater's bow for wool carding.

Grading and classification of wool depends on its thickness. The smaller grades appropriate to thicker filaments at 8-10-12-16-18-20-24.

Raw wool has 16 to 70 percent of un-purity. 90% of wool filaments are formed of the skin cells, which supply drafting force of the filaments around 20 to 40 percent of the length. Also they secure its natural color.

A filament of the wool may be seen under a magnifier lens as a trunk of pine tree with clear irregular scales and free edges. 
This wool could not be used for carpet weaving. In the meantime, the cellulose of wool-like filaments are not adequate for carpet because of low quality.
The best wool could be cut out of the shoulder and belly of the sheep. Therefore, if we want to have a uniform monotonous carpet, the wool must be cut out of one organ of the sheep for spinning.
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