The Vertical Stripe Paintings are a series of stain paintings from the early 1990s produced with a delineated process for creating the stripes and using gravity to distribute the paint. A limited number of layers of pigment were applied in a series of oppositions—left to right, right to left, edge to center and center to edge—such that the individual layers and process is revealed in the completed piece. As with most of his paintings, Martinelli uses transparent layers of color and process to explore color relationships and harmonies.