The mural "The Underground Railroad" is a fresco. The word fresco is an Italian word meaning "fresh". This describes what a fresco is because it is a painting technique done on wet or fresh plaster. The painting had to be completed quickly while the plaster was still wet. Because of this, the fresco technique didn't allow the artists time to include many details in the picture. To make a fresco, the artist first made a charcoal drawing on the wall completing as much of the drawing as he could in a single day. The artist next spread a thin coat of wet plaster over the dry wall retracing the charcoal lines which he could barely see underneath. Paint mixed with water and egg whites was applied directly to the wet plaster. The paint and wet plaster bonded together to form a permanent surface. Sometimes artists painted over the surface after it dried, however this layer of paint usually flaked off in time. If a mistake was made, the white surface had to be cleaned off and the section done again.