There are three main forms of sculptural relief panel and two lesser used techniques. This sculptural term originates in the Italian ‘relievare’, to raise. (ie. an art work that projects from the supporting background and to be viewed from one side), and they are classified by the distances at which they protrude from the back.
High Relief (Alto-Rilievo or Haut Relief)
This is where more than 60% of the depth is shown and there are deeply undercut areas allowing for much more shadow and in a sense greater drama. Some figures will be seen practically in the round. This is the predominant carving technique for the relief work in the temples of India and during the Italian Renaissance.
Mid Relief (Mezzo-Rilievo, Demi-Relief)
This technique defined by having half the forms appearing to be below the surface, half emerging feeling from the clay base. The visual sensation is of a full form and is reliant on strong side light to cast the most shadow and create visual depth and is seen in the Persian /Iranian pieces in temples.
Low Relief (Basso-Rilievo, Bas-Relief)
This is a subtle smooth relief used predominantly in coins and no part is fully detached from the background.
Flat Relief (Relievo Sticciato or Staccato)
Stiacciato relief is an extremely subtle type of flat, low relief carving that is especially associated with the 15th-century sculptor Donatello who’s background images are predominantly drawn into the surface of the clay. The design is partly drawn with finely engraved chisel lines and partly carved in relief.
Hollow or Concave Relief (Cavo-Relievo)
This is relief in reverse, in which all the carving lies within a hollowed-out area below the surface plane, and is clearly seen in the tombs and stellae of Ancient Egypt. The dramatic lower sunlight of dawn and dusk casting deep shadows into the surface making the carving visually seem to protrude forwards.
Incised Relief (Intaglio-Rilievato)
This is carved down into the surface of the relief resulting in an optical illusion of a protruding form. This can be found in the carved decoration found on precious stones, and for making moulds for coins by the Ancient Greeks and Romans (and not to be confused with hollow relief) as the image was fully carved negatively into the surface, so that when impressed with wax it gives an impression. For example a wax seal or the mould for a coin or a cameo.