The presence of zinc oxide oil paint and the condition problems observed in a group of paintings from the collection of the Hirshhorn Museum and Sculpture Garden prompted analytical examination of the museum’s mid-20th century holdings. Results reveal a link between upper layer deterioration and underlying zinc oxide paint layers, and suggest that certain visible signs of deterioration may signal the presence of more serious and wide-spread condition problems. The popularity of zinc oxide house paint among mid-century artists creates a higher probability of this type of deterioration in works from this period.