The Two Principles of Sculpture

The process of sculpting can be broken down into two basic principles, additive and subtractive. Which of these principles is needed is largely dictated by the material that sculptor plans to use, as well as the nature of the piece that is being created.

Additive

Additive is, as you might imagine, the process of piecing or adding material together to build outwards the desired form of the sculpture.

Subtractive

Subtractive is the opposite, whereby the material is carved out or removed systematically in such a way as to "reveal" the sculpture.

And four basic ways to use them

Of the four basic sculpture techniques, three are additive and one subtractive.

Carving

Carving sees the sculptor use a variety of tools to create a sculpture by carving out, or removing material. Commonly stone and wooden sculptures are made in this way. For example a block of stone can be chipped away using a chisel. Any material that is hard enough to keep its form when portions of it are removed could be subject to this subtractive process. Aside from stone and wood, ivory and ice are also common materials used with the carving technique.

Casting

Casting is typically used to create metal sculptures, however other materials can also be used such as plaster, concrete or resin. A liquid material is poured into a mold where in time it then sets producing a solid sculpture. Typically sculptures created using this additive technique are metal, with bronze being perhaps the type of metal most frequently used.

Sculptor carving stone by Uusi Suomi [Public domain]

Metal being poured into a cast by Takkk (Own work) (CC BY-SA 3.0) via Wikimedia Commons.

Modelling

Modelling is an additive technique. The process of sculptural modelling is to take a soft material such as clay and manipulate it and shape it into the desired form. Additional pieces of the material can be added to build up the sculpture.

Assembling

Assembling is a technique frequently used in the creation of contemporary or modern works of art and came to prominence during the 20th century. A vast number of materials are available to the modern sculptor and through this additive process, materials are collected and pieced together to assemble a sculpture.

An example of a modelled sculpture process. Photograph by Roland zh (Own work) (CC BY-SA 3.0) via Wikimedia Commons

Life-size assembled metal sculpture of Hugh Glass being mauled by a Grizzly Bear. John Lee Lopez (Own work) (CC BY-SA 4.0) via Wikimedia Commons