These relief paintings, typically oil over x-rays, will eventually serve as molds for castings. During the process the paintings are x-rayed. The x-rays are then used as a source index for constructing a mold for casting (as is the case for antepurgatorio, door, bed). There is a constant processual dialog–correspondences–between the indexical x-ray image and emergent painting that often results in a diptych or triptych, as in homage to angelus novus and unpropped: book for r. serra.