illivelli ta impuritajiet joniċi filmaterjali koloranti li jintużaw ma għandhomx jaqbżu llivelli li ġejjin ag 100 ppm as 50 ppm ba 100 ppm cd 20 ppm co 500 ppm cr 100 ppm cu 250 ppm fe 2500 ppm hg 4 ppm mn 1000 ppm ni 200 ppm pb 100 ppm se 20 ppm sb 50 ppm sn 250 ppm zn 1500 ppm