He was noted for his wide range of subjects and his interest in social issues, and was an associate of the post-Impressionists Ştefan Luchian and Constantin Artachino, as well as a friend of the controversial art collector and political figure Alexandru Bogdan-Piteşti.

Isidor adopted his father's pseudonym "Vermont" (the name being a gallicization of Grünberg — literally, "green mountain") and, upon converting to the Romanian Orthodox Church,[2] took the first name Nicolae.

[2] In parallel, with Luchian, Juan Alexandru Paraschivescu-Alpar, and Artachino, Vermont was one of the first to introduce themes related to the lives of unemployed individuals and social drifters.

[8] Two years after Salonul Independenţilor opened for the public, its initiators (together with Ioan Bacalbaşa) founded Societatea Ileana, an association dedicated to promoting new styles in art.

[9] In 1906, during the 40th celebration of King Carol I's ascension to the Romanian throne, Vermont's paintings were exhibited in Bucharest alongside the works of Grigorescu, Verona and Loghi (they won the admiration of Krikor Zambaccian, the future art collector, who declared himself "obsessed" with their image).