Clown Making Up displays the vigorous brushwork of Sloan's early style and also reveals his intensified interest in color theory—the result of experimentation with principles to which Robert Henri had introduced him in 1909. For Clown Making Up, Sloan limited the palette to purple, yellow-orange, and green. The flickering candlelight casts green, not gray, shadows on the tired clown's face and garb, evidence not only of Sloan's interest in the color of shadows, but also of his use of chiaroscuro (dramatic contrasts between light and darkness) to heighten the sculptural quality of the figure. Set within a shallow, stage-like setting, the clown is pushed to the front of the picture plane by loosely defined shapes suggesting a circus tent. Sloan chose to depict the clown just as he was starting to apply his makeup, thus concentrating on the human being behind the façade.
Duncan Phillips, whose early taste in art included narratives and romantic subjects, was undoubtedly attracted to the intimate quality of Clown Making Up. He acquired it in 1919, and later interpreted it in A Collection in the Making as the depiction of a "lonely individual caught in the maelstrom—the tired old clown, who must be funny, 'making up' his haggard face by candle-light in some dusty dressing room..."