His painting style was influenced by Cubism, which he taught during his tenure as a leading lecturer of Modern Art in Indonesia.
He also made contact with Otto van Rees (artist), Lambert Simon and Charles Eyck.
Works by Breitner, Paul Citroen, Wally Moes, Otto van Rees and by many others are on display.
For five years she was imprisoned in the Japanese internment camps Tjilatjap, Tjimahi (Cimahi) and Pekanbaru, where she worked as a barracks nurse or in a military hospital.
[6] During world War II, Ries met in the Japanese prison camp and together they made plans to start training art teachers in Bandung.
[7] Finally, in 1947, Simon Admiraal got permission from the Dutch Government to start the Art Teacher University Course in Bandung.
Before the war he mainly made figurative and impressionistic paintings, but his work is now increasingly abstract and the influence of Otto van Rees and Charles Eyck is evident.
Subjects are laid out into angular geometric shapes, separated from each other by sharp black lines (stained glass).
As both a painter and lecturer, Ries Mulder, began inserting abstract art into his teaching at the Bandung Institute of Technology (ITB) in the 1950s, hence giving birth to a new generation of artists, such as But Muchtar, Mochtar Apin, Ahmad Sadali and Rita Widagdo.
In the same year 1954, assistant teachers and students of the Art Faculty in Bandung organized an exhibition for 11 painters, that featured their experimentation in a cubist style.
This exhibition showed works of Ahmad Sadali, But Muchtar, Popo Iskandar and Kartono Yodhukusumo created significant furor and controversy.
The painter and art critic Trisno Sumardjo decried the works as "bloodless, formal, self-absorbed, not grounded in the reality of their country and its environment and social issues".
It was this exhibition, that started the debate "East versus West", e.g. criticizing Ries Mulder as eradicating Indonesian art values by conveying European norms.
His later works consist mainly of cityscapes in soft pastel colors, built on geometric planes and separated from each other by black contours.