Various techniques for coloring carpet yarns, including beck dyeing (immersion in dye baths), continuous dyeing (application after tufting), space dyeing (multiple colors on a single yarn), and solution dyeing (color added to liquid polymer before extrusion). Each method offers different benefits for colorfastness, pattern capabilities, and environmental impact. In hand-knotted rugs the wool is dyed as spun yarn before knotting, with natural dyes from plants, roots, and flowers, which tend to mellow with age, or with synthetic dyes; differences between dye batches are a main source of abrash.