Cornelis was a very successful entrepreneur and that allowed him to become one of the most important art collectors from the Netherlands. Besides collecting drawings he was also interested in the scientific aspect of print making and experimented constantly in seeking new techniques to make etchings in a drawing alike style that reproduced his important collection. He experimented with printing in colour from several plates. He can be called a real inventor and brought the technique of printing to a new level. His working methods have been revealed by Th. Laurentius and catalogued in the work 'Cornelis Ploos van Amstel' Kunstverzamelaar en prentuitgever, published in 1980.

He worked with other printmakers who were obliged to keep the newly invented techniques secret. Some of his assistants include Bernard Schreuder, Elisabeth van Woensel, Cornelis Buys, Cornelis Brouwer. His printer was Johannes Körlein. Son-in-law of Cornelis Troost

Jurriaan Cootwyck ( 1714 - died 1798)

Silversmith from profession.  He made drawings and etchings mostly after old masters like Van Ostade, Potter, Rembrandt a.s.o. He worked also in the Ploos van Amstel technique (Vernis-dur). He was older then Ploos and died only 11 months before Ploos. It seems Josi who intended to finish the publication work started by Ploos came in the possession of the stock left after Cootwyck's death and used it together with the plates by Ploos in his publication. The edition was limited to 100 so less the the Ploos edition of 350.
 

SAINT FRANCISCUS S.Francis Reference: Wurzbach 5                                  12,50 by 8,60 cm Rijksmuseum Amsterdam Inv. RP-P-1882-A-5601 Signature in pencil on backside : J Cootwyck Fecit (original own handed signature) Design: Abraham Bloemaert (1564-1651) Engraver: Jurrian Cootwyck ( 1714 - died 1798) Technique: Printdrawing in brown.
CHERUBIJNEN MET EEN WAPENSCHILD Cherubs with coat-of -arms Three cherubs holding a coat-of-arms with the proverb: 'Felisitas Publica' Reference: Wurtzbach 12          11,70 by 11,40 cm Rijksmuseum Amsterdam Inv. RP-P-1882-A-6777 J Cootwyck Fecit (original own handed signature on the backside) Drawer: Jacob de Wit (1695-1754) Engraver: Jurrian Cootwyck ( 1714 - died 1798) Technique: Printdrawing in sepia-brown.	HAGAR IN DE WOESTIJN Hagar in the desert Hagar lying on the ground in a mountainous landscape. An angel points here towards a well.  On the right Ismail, the child of Hagar hidden under a bush. Reference: Wurtzbach 21. B          13,50 by 17,50 cm Rijksmuseum Amsterdam Inv. RP-P-1882-A-5601 J Cootwyck Fecit (original own handed signature on the backside) L Sueur D 1759 (date and signature inside plate border) Drawer: Eustache Lesueur  (1616-1665) Engraver: Jurrian Cootwyck ( 1714 - died 1798) Technique: Printdrawing in sepia-brown. Three variants are known (A-B-C) This is B; proof state