In former times, kris blades were said to be infused with poison during their forging, ensuring that any injury was fatal. The poison used to polish kris blade is called . The process of chemical coating was done by or (washing) the blade with acid and minerals that contains arsenic compounds. The process of doing so was kept secret among smiths. Different types of whetstones, acidic juice of citrus fruits and poisonous arsenic bring out the contrast between the dark black iron and the light colored silvery nickel layers which together form , damascene patterns on the blade.