Silver Overlay is a process of soldering one piece of silver, from which a design has been cut, over another piece of silver. The top layer is a handmade, hand cut overlay created from a sheet of sterling that is then bonded to the base layer of sterling. The base layer background is usually oxidized, which turns the silver surface black, and is often scratched or stamped. The oxidation brings out a contrast between the two pieces and makes the individual designs more visible. This technique used in Hopi jewelry was developed out of a project initiated by the Museum of Northern Arizona in 1930 to encourage the Hopi to develop their own unique jewelry, distinguishable from other Native American silversmiths. Hopi overlay pieces often tell a story, incorporating several images into one piece of jewelry.