Using 3 different types of steel in this planter allows varying patinas to develop to create unique colors, textures and accents.  The top rim is cold rolled steel which patinas readily and consistently, yielding a leathery brown finish.  The sides of the planter are hot rolled sheet which develops a more irregular and organic patina, evidenced by the browns and oranges.  Finally, using hot rolled steel angle at the corners provides a steely color accent - undergoing the slowest transformation of surface patina.