▁of ▁in k ▁are ▁mixed , ▁each ▁of ▁a ▁different ▁vis cos ity . ▁This ▁vis cos ity ▁is ▁adjust ed ▁by ▁the ▁addition ▁of ▁un co oked ▁lin seed ▁oil . ▁▁ ▁Metal ▁pl ates , ▁usually ▁co pper ▁or ▁z inc , ▁are ▁used , ▁as ▁in ▁the ▁int ag lio ▁processes . ▁The ▁artist ▁produces ▁images ▁on ▁the ▁plate ▁by ▁et ch ing ▁lines ▁or ▁text ures . ▁The ▁plate ▁is ▁then ▁in ked ▁in ▁several ▁stages . ▁The ▁first ▁in k ▁would ▁be ▁fairly ▁dense — of ▁a ▁relatively ▁high ▁vis cos ity . ▁The ▁application ▁of ▁the ▁high - vis cos ity ▁in k ▁is ▁carried ▁out ▁as ▁in ▁any ▁int ag lio ▁process : ▁by ▁forcing ▁it ▁into ▁the ▁re cess es ▁of ▁the ▁plate ▁and ▁then ▁w ip ing ▁off ▁the ▁plate ' s ▁surface ▁with ▁a ▁tar lat an . ▁ ▁In k ▁of ▁a ▁second ▁color , ▁and ▁the ▁th inn est ▁vis cos ity , ▁is ▁then ▁applied ▁to ▁the ▁surface ▁of ▁the ▁plate ▁with ▁a ▁hard ▁rub ber ▁roll er , ▁so ▁that ▁it ▁covers ▁the ▁plate ▁in ▁one ▁pass ▁and ▁only ▁trans fers ▁onto ▁the ▁highest ▁areas ▁of ▁the ▁plate . ▁In k ▁of ▁a ▁third ▁color , ▁and ▁a ▁much ▁st iffer ▁consist ency , ▁is ▁then ▁applied ▁to ▁the ▁lower ▁areas ▁of ▁the ▁plate ▁with ▁a ▁so fter ▁rub ber ▁roll er . ▁The ▁varying ▁vis cos ities ▁of ▁the ▁two ▁rolled - on ▁in ks ▁prevent ▁them ▁from