▁by ▁Korean ▁artists . ▁In ▁ 1 4 6 3 ▁when ▁sources ▁of ▁c ob alt ▁were ▁discovered ▁in ▁Korea , ▁artists ▁and ▁their ▁buy ers ▁found ▁the ▁material ▁was ▁inferior ▁in ▁quality ▁and ▁preferred ▁the ▁more ▁expensive ▁imported ▁c ob alt . ▁Korean ▁por cel ain ▁with ▁imported ▁c ob alt ▁decor ation ▁contradict ▁the ▁emphas is ▁of ▁an ▁order ly , ▁f rug al ▁and ▁moder ate ▁life ▁in ▁Ne o - Conf u cian ism . ▁ ▁St rik ingly ▁different ▁from ▁c ob alt , ▁por cel ain ▁items ▁with ▁a ▁co pper - red ▁under g la ze ▁are ▁the ▁most ▁difficult ▁to ▁successfully ▁craft . ▁During ▁production , ▁these ▁items ▁require ▁great ▁skill ▁and ▁attention ▁or ▁will ▁turn ▁gray ▁during ▁the ▁process ▁of ▁firing . ▁While ▁the ▁birth place ▁of ▁cer am ics ▁with ▁co pper ▁red ▁under g la ze ▁is ▁widely ▁disput ed , ▁these ▁items ▁origin ated ▁during ▁ 1 2 th ▁century ▁in ▁Korea ▁and ▁became ▁increasing ly ▁popular ▁during ▁the ▁second ▁half ▁of ▁the ▁Jose on ▁period . ▁Some ▁exper ts ▁have ▁pointed ▁to ▁the ▁kil ns ▁of ▁Bun won - ri ▁in ▁G w ang ju , ▁G ye ong gi , ▁a ▁city ▁that ▁played ▁a ▁significant ▁role ▁in ▁the ▁production ▁of ▁cer am ics ▁during ▁the ▁Jose on ▁period , ▁as ▁a ▁possible ▁birth place . ▁ ▁Por cel ain ▁was ▁also ▁decor ated ▁with ▁iron . ▁These ▁items ▁commonly ▁consisted ▁of ▁j ars ▁or ▁other ▁util itar ian