▁co pper ▁by ▁ 2 3 % ▁and ▁a ▁b ism uth ▁content ▁of ▁just ▁ 0 . 0 0 1 % ▁makes ▁co pper ▁brit t le . ▁The ▁material ▁used ▁in ▁the ▁c ath ode ▁must ▁not ▁cont amin ate ▁the ▁co pper ▁being ▁depos ited , ▁or ▁it ▁will ▁not ▁meet ▁the ▁required ▁specific ations . ▁ ▁The ▁current ▁efficiency ▁of ▁the ▁ref ining ▁process ▁depends , ▁in ▁part , ▁on ▁how ▁close ▁the ▁an odes ▁and ▁c ath odes ▁can ▁be ▁placed ▁in ▁the ▁electro ly t ic ▁cell . ▁This , ▁in ▁turn , ▁depends ▁on ▁the ▁straight ness ▁of ▁both ▁the ▁an ode ▁and ▁the ▁c ath ode . ▁B umps ▁and ▁b ends ▁in ▁either ▁can ▁lead ▁to ▁short - circ uit ing ▁or ▁otherwise ▁affect ▁the ▁current ▁distribution ▁and ▁also ▁the ▁quality ▁of ▁the ▁c ath ode ▁co pper . ▁ ▁Prior ▁to ▁the ▁development ▁of ▁the ▁Isa ▁Process ▁technology , ▁the ▁standard ▁approach ▁was ▁to ▁use ▁a ▁st arter ▁sheet ▁of ▁high - p urity ▁co pper ▁as ▁the ▁initial ▁c ath ode . ▁These ▁st arter ▁sheets ▁are ▁produced ▁in ▁special ▁electro ly t ic ▁cells ▁by ▁electro de position ▁of ▁co pper ▁for ▁ 2 4 ▁hours ▁onto ▁a ▁plate ▁made ▁of ▁co pper ▁co ated ▁with ▁oil ▁( or ▁treated ▁with ▁other ▁similar ▁face - separ ation ▁materials ) ▁or ▁of ▁tit an ium . ▁Th ous ands ▁of ▁sheets ▁could ▁be ▁needed ▁every ▁day , ▁and ▁the ▁original ▁method ▁of