▁who ▁taught ▁him ▁many ▁aspects ▁of ▁the ▁process ▁based ▁on ▁simple ▁techniques , ▁including ▁how ▁to ▁operate ▁the ▁press , ▁and ▁how ▁to ▁prepare ▁the ▁stones . ▁H elf ond ▁played ▁a ▁significant ▁role ▁as ▁a ▁teacher ▁of ▁l ith ography ▁at ▁the ▁Har lem ▁Art ▁Center . ▁Joseph ▁produced ▁his ▁first ▁l ith ograph s ▁under ▁her ▁super vision , ▁and ▁this ▁was ▁at ▁a ▁time ▁when ▁she ▁was ▁just ▁beginning ▁to ▁learn ▁the ▁medium ▁herself . ▁▁ ▁At ▁the ▁Har lem ▁Community ▁Arts ▁Center ▁Joseph ▁met ▁Robert ▁Black burn , ▁who ▁was ▁his ▁class mate . ▁In ▁ 1 9 3 7 ▁Ron ald ▁Joseph ▁dep icted ▁Black burn , ▁in ▁one ▁of ▁his ▁most ▁famous ▁works , ▁that ▁is ▁now ▁located ▁at ▁The ▁Metropolitan ▁Museum ▁collection . ▁Ex periment ing ▁with ▁l ith ography ▁and ▁et ch ing , ▁as ▁well ▁as ▁wood block ▁and ▁sil ks creen ▁printing , ▁Joseph ▁expl ored ▁the ▁techniques ▁of ▁print making ▁alongside ▁his ▁friend ▁Robert ▁Black burn . ▁▁ ▁Joseph ▁described ▁the ▁Har lem ▁Art ▁Center ▁as ▁a ▁" he alth y ▁and ▁l ively " ▁place , ▁where ▁he ▁had ▁made ▁wonderful ▁friends . ▁ ▁In ▁the ▁late ▁th irt ies , ▁he ▁also ▁served ▁as ▁a ▁teacher ▁at ▁the ▁Har lem ▁Community ▁Arts ▁Center . ▁There ▁Joseph ▁met ▁younger ▁artist ▁Jacob ▁Lawrence ▁and ▁G wend ol yn ▁Knight . ▁They ▁formed ▁a ▁friendship , ▁where ▁they ▁enjoyed ▁convers ations ▁and ▁visit ing ▁museum s ▁together . ▁Both ▁Joseph ▁and ▁Knight ▁would