In the mid 60s, Serra became a leading innovator in working with soft sculptural materials. He was attracted by the malleability of certain materials and their capacity to reflect the process of making. I’m interested in revealing the structure and content and character of a space and a place by defining a physical structure through the elements that I use."
Gravity became a central issue in Serra’s work during the winter of 1969-70. He was experimenting with molten lead, which he splashed against a small steel plate that was wedged in a corner of his studio. He realized that if the angle of the floor and walls alone would hold up this small plate, it would also support a large steel plate. Thus began what is known as the Prop series, in which he explored the tensions that arise out of the combination of massive weight, gravity, and balance - huge plates of lead or rolled steel leaning against each other, supported only by their weight, without recourse to such devices as clips, gluing, or welding. The weight and density of the work, in con-junction with gravity, held the structures together. The steel plate series included the additional element of space as a dimension that could be altered or redefined.