▁mixing . ▁A ▁fourth ▁color , ▁of ▁even ▁th inner ▁vis cos ity , ▁can ▁also ▁be ▁applied ▁at ▁this ▁point . ▁This ▁color ▁is ▁either ▁spread ▁out ▁on ▁a ▁glass ▁plate , ▁which ▁is ▁then ▁pressed ▁against ▁the ▁printing ▁plate ▁so ▁that ▁the ▁in k ▁only ▁ad her es ▁to ▁the ▁highest ▁points ▁of ▁the ▁metal ▁plate , ▁or ▁it ▁is ▁applied ▁ ▁by ▁a ▁hard ▁roll er ▁applied ▁with ▁very ▁little ▁pressure . ▁ ▁This ▁process ▁may ▁be ▁done ▁with ▁a ▁monot ype ▁as ▁well . ▁In king ▁the ▁ac ry lic ▁or ▁p lex ig lass ▁plate ▁with ▁one ▁in k ▁with ▁a ▁very ▁high ▁vis cos ity , ▁and ▁following ▁that , ▁rolling ▁a ▁very ▁loose ▁in k ▁over ▁it , ▁produces ▁two ▁t ones ▁on ▁a ▁single ▁plate . ▁One ▁may ▁attempt ▁to ▁scratch ▁an ▁image ▁onto ▁the ▁plate , ▁but ▁ac ry lic ▁and ▁p lex ig lass ▁pl ates ▁are ▁more ▁temper amental ▁than ▁co pper ▁or ▁z inc , ▁and ▁wear ▁out ▁sooner . ▁ ▁A ▁sheet ▁of ▁printing ▁paper ▁is ▁then ▁placed ▁on ▁the ▁u pr ight ▁plate ▁and ▁passed ▁through ▁a ▁printing ▁press , ▁which ▁prints ▁all ▁of ▁the ▁colors ▁simultaneously . ▁This ▁is ▁of ▁a ▁certain ▁advantage , ▁as ▁in ▁some ▁other ▁multi - color ▁printing ▁processes , ▁correct ▁registration ▁of ▁the ▁blocks ▁presents ▁a ▁difficulty . ▁ ▁See ▁also ▁ ▁Mon ot yp ing ▁ ▁References ▁ ▁Further ▁reading ▁ ▁N I U ▁Te chni ques ▁Page ▁▁▁ ▁Vis cos ity