She also studied with Charles Webster Hawthorne at the National Academy of Design in New York where she befriended artists Esphyr Slobodkina and Ilya Bolotowsky.

During one stay at a rehabilitation clinic, she met and befriended Richard ("Dick") Bellamy, who would later exhibit her at Hansa Gallery in 1959.

"[9] Mason remained quite active until her last years of life, exhibiting frequently in gallery shows and having institutions, like the Whitney and Brooklyn Museum, acquire her work.

This monograph details Mason's artistic process, painting style, activism, printmaking, poetry, and letters.

[13] Mason's intimate and experimental abstractions began in a biomorphic style and became increasingly geometric over time.

"[14] As New York Times critic Holland Cotter observed, Mason's paintings show how "rigorous, stimulating, and accessible" abstraction can be.

[15] In 2020, Roberta Smith of the New York Times wrote of Mason's trajectory, "The forms on her small canvases mutated with unusual variety and momentum between the biomorphic and geometric (the latter ultimately won out).

In other words, the initial influence of Kandinsky (and also Joan Miró) gave way to that of Piet Mondrian, on whose legacy she built with an originality that few other American painters have equaled.