Johannes Hendricus (Johan) Hartgring was born in 1876 in The Hague as the son of a stonemason and was the younger brother of WP Hartgring. He started as a learner at Rozenburg in 1892 and worked there with two interruptions until January 1898 when he left as a journeyman. He moved to Gouda in November 1898 but can have commuted in the period in between. For whatever reason, he moved back and forth several times between Gouda and the Hague in the following years but probably commuted to Gouda to work at PZH. He is known to have been a designer of decors as well as a decorator, and he remained at PZH until 1928. He passed away in Gouda in 1951.
His oeuvre seems to indicate he did work at PZH from early 1898.