In 1998, Ortiz-Hernández turned from brightly colored figurative paintings to making simple geometric forms on paper using graphite. She is inspired by the black and white tenebrist drawings of Georges Seurat as well as by the explorations of modernist artists such as Kazemir Malevich, who sought universality in geometric forms. Sum IV exemplifies Ortiz-Hernández's interest in seriality. Made of numerous layers of almost imperceptible strokes of graphite, the five squares that comprise this series of drawings progress from dark to light. Each of the individual squares, however, is remarkably uniform, lending it an object-like appearance, as if it might lift off the page. There is a subtle commentary in her combination of geometry with perceptual instability.