color . ▁In ▁ 1 9 5 9 ▁and ▁ 1 9 6 0 , ▁he ▁expl ored ▁the ▁writ ings ▁of ▁Go ethe ▁and ▁Kant . ▁ ▁In fl uen ced ▁by ▁Go ethe ' s ▁color ▁theories , ▁he ▁began ▁to ▁pre face ▁the ▁titles ▁of ▁his ▁works ▁with ▁the ▁word ▁" P hen omena " ▁followed ▁by ▁a ▁key ▁word ▁or ▁phrase . ▁Regarding ▁his ▁paint ings , ▁he ▁once ▁said , ▁" I ▁have ▁convers ations ▁with ▁them , ▁ ▁and ▁they ▁tell ▁me ▁what ▁they ▁want ▁to ▁be ▁called ." ▁▁ 1 9 6 0 s ▁Grad ually ▁in ▁ 1 9 6 0 ▁he ▁moved ▁away ▁from ▁working ▁in ▁oil ▁on ▁canvas ▁to ▁ac ry lic . ▁Jenkins ▁began ▁to ▁paint ▁using ▁an ▁iv ory ▁kn ife , ▁a ▁key ▁tool ▁in ▁the ▁creation ▁of ▁his ▁work : ▁ ▁The ▁art ▁historian ▁Albert ▁E . ▁El sen ▁has ▁noted : ▁" J enkins ▁was ▁not ▁st aining ▁his ▁canvas , ▁because ▁of ▁the ▁s izing ▁and ▁prim ing ." ▁ ▁Through out ▁the ▁ 6 0 s , ▁his ▁work ▁was ▁shown ▁world wide , ▁at ▁major ▁gall eries ▁and ▁museum s ▁in ▁Tokyo , ▁London , ▁New ▁York , ▁Paris , ▁Amsterdam ▁and ▁elsewhere . ▁ ▁In ▁ 1 9 6 3 , ▁he ▁took ▁over ▁Wille m ▁de ▁K oon ing ' s ▁light - inf used ▁lo ft ▁at ▁Union ▁Square ▁in ▁New ▁York ▁City ▁where ▁he ▁worked ▁until ▁the ▁end ▁of ▁ 2