Yeomsaekjang refers to a craftsman who dyes cloth with natural pigments. Specifically, the art of dyeing, which has been designated as Important Intangible Cultural Heritage, involves dyeing with indigo. In the Joseon Dynasty, dyeing was a highly specialized skill such that a dyeing specialist was attached to the royal court. Natural dyes used for coloring cloth are plant, mineral, or animal matter, used as is or slightly processed. There are all kinds of dyes, but the indigo bush (Persicaria tinctoria) was the most difficult to use; the complicated dyeing process also required a high level of skill. With modernization as well as the introduction of chemical dyes, traditional dyeing has all but vanished. Thanks to a handful of dedicated craftsmen who have worked to revive the art since the 1970s, however, the art has been kept alive.