Sculptors primarily use four basic techniques. The processes are either subtractive (material is removed or carved out) or additive (material is added).
Carving: Carving involves cutting or chipping away a shape from a mass of stone, wood, or other hard material. Carving is a subtractive process whereby material is systematically eliminated from the outside in.
Casting: Sculptures that are cast are made from a material that is melted down—usually a metal—that is then poured into a mold. The mold is allowed to cool, thereby hardening the metal, usually bronze. Casting is an additive process.
Modeling: Modeled sculptures are created when a soft or malleable material (such as clay) is built up (sometimes over an armature) and shaped to create a form. Modeling is an additive process.
Assembling: Sculptors gather and join different materials to create an assembled sculpture. Assembling is an additive process. An example of assemblage is Martin Puryear's That Profile, above.