He worked in a variety of media including etching, lithography, water color, monotype, linocut, woodcut, oil, photography, mezzotint and silversmithing.

The results of this first year's training in a type of work so entirely new to Teachers College students are highly gratifying to Professor Dow.

O'Keeffe considered Martin's instruction significant enough that she continued sending examples of her work for his critique in the period after she attended his class.

Mr. C. went back to [Charles'] picture three times and stood for ages admiring and commenting upon it – thought the light and shadows perfect and loved the simplicity of the theme.

Martin spent many summers in the 1920s–50s living and teaching plein air art classes in Provincetown, Mass,[7] and also in Mexico.

[9] At Teachers College, Martin met a fellow art student named Esther L. Upton, whom he eventually married.

But the artist in this instance has had also a sense of humor and a conscience, and since his room is a human abode he has analyzed its character and made of his work a witty and penetrating comment.

Martin's method makes water color a thing to reckon with at a distance, a medium capable of decorative effect.

He pays tribute to the peculiar character of the medium, its sparkling idiosyncrasy, by his use of the white outline, which detaches the masses of color from one another, keeping them in one plane as effectively as the black bounding line in favor with one school of modern painters; and which has the advantage of giving the white ground of the paper a chance to play its enlivening part in the general scheme.

[11]Charles J. Martin, well known for his freedom from academic restraint in his method of teaching design, achieves an equally unhampered expression in his creative work.

In contrast to the rugged construction of this work is the fluent character of the "Sand Pit," where the harmonic tour de force of combining warm and cold tonalities is skillfully accomplished.