The art of carpet weaving in Iran dates backs to 2,500 years and is rooted in the culture and customs of its people and their instinctive feelings. Weavers mix elegant patterns with a myriad of colors.
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The Iranian carpet is similar to the Persian garden: full of florae, birds and beasts. The colors are usually extracted from wild flowers, and are rich in colors such as burgundy, navy blue and accents of ivory.
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The proto-fabric is often washed in tea to soften the texture, giving it a unique quality. Depending on where the rug is made, patterns and designs vary.

http://www.iranreview.org/content/Documents/Iran%E2%80%99s_Art_Heritages_and_Handicrafts.htm