Basically, concrete is a mixture of an aggregate (usually sand and small pieces of stone) bound together by cement. A variety of stones, such as crushed marble, granite chips, and gravel, can be used, each giving a different effect of colour and texture. Commercial cement is gray, white, or black; but it can be coloured by additives. The cement most widely used by sculptors is ciment fondu, which is extremely hard and quick setting. A recent invention—at least, in appropriate forms for sculpture—concrete is rapidly replacing stone for certain types of work. Because it is cheap, hard, tough, and durable, it is particularly suitable for large outdoor projects, especially decorative wall surfaces. With proper reinforcement it permits great freedom of design. And by using techniques similar to those of the building industry, sculptors are able to create works in concrete on a gigantic scale.

When synthetic resins, especially polyesters, are reinforced with laminations of glass fibre, the result is a lightweight shell that is extremely strong, hard, and durable. It is usually known simply as fibreglass. After having been successfully used for car bodies, boat hulls, and the like, it has developed recently into an important material for sculpture. Because the material is visually unattractive in itself, it is usually coloured by means of fillers and pigments. It was first used in sculpture in conjunction with powdered metal fillers in order to produce cheap “cold-cast” substitutes for bronze and aluminum, but with the recent tendency to use bright colours in sculpture it is now often coloured either by pigmenting the material itself or by painting. It is possible to model fibreglass, but more usually it is cast as a laminated shell.

Various formulas for modeling wax have been used in the past, but these have been generally replaced by synthetic waxes. The main uses of wax in sculpture have been as a preliminary modeling material for metal casting by the lost-wax, or cire-perdue, process (see Methods and techniques, below) and for making sketches. It is not durable enough for use as a material in its own right, although it has been used for small works, such as wax fruit, that can be kept under a glass dome.

Papier-mâché (pulped paper bonded with glue) has been used for sculpture, especially in the Far East. Mainly used for applied arts, especially masks, it can have considerable strength; the Japanese, for example, made armour from it. Sculpture made of sheet paper is a limited art form used only for ephemeral and usually trivial work.

Numerous other permanent materials—such as shells, amber, and brick—and ephemeral ones—such as feathers, baker’s dough, sugar, bird seed, foliage, ice and snow, and cake icing—have been used for fashioning three-dimensional images. In view of late 20th-century trends in sculpture it is no longer possible to speak of “the materials of sculpture.” Modern sculpture has no special materials. Any material, natural or man-made, is likely to be used, including inflated polyethylene, foam rubber, expanded polystyrene, fabrics, and neon tubes; the materials for a sculpture by Claes Oldenburg, for example, are listed as canvas, cloth, Dacron, metal, foam rubber, and Plexiglas. Real objects, too, may be incorporated in sculpture, as in the mixed-medium compositions of Edward Kienholz; even junk has its devotees, who fashion “junk” sculpture. Food was also used, as in the brightly coloured wrapped candy of Felix Gonzalez-Torres’s “Untitled” (Portrait of Ross in L.A.) (1991), the sugar of Kara Walker’s A Subtlety, or the Marvelous Sugar Baby (2014), and a banana in Maurizio Cattelan’s conceptual piece Comedian (2019).

The sculptor as designer and as craftsman

The conception of an artifact or a work of art—its form, imaginative content, and expressiveness—is the concern of a designer, and it should be distinguished from the execution of the work in a particular technique and material, which is the task of a craftsman. A sculptor often functions as both designer and craftsman, but these two aspects of sculpture may be separated.

Certain types of sculpture depend considerably for their aesthetic effect on the way in which their material has been directly manipulated by the artist. The direct, expressive handling of clay in a model by Rodin, or the use of the chisel in the stiacciato (very low) reliefs of the 15th-century Florentine sculptor Donatello could no more have been delegated to a craftsman than could the brushwork of Rembrandt. The actual physical process of working materials is for many sculptors an integral part of the art of sculpture, and their response to the working qualities of the material—such as its plasticity, hardness, and texture—is evident in the finished work. Design and craftsmanship are intimately fused in such a work, which is a highly personal expression.

Even when the direct handling of material is not as vital as this to the expressiveness of the work, it still may be impossible to separate the roles of the artist as designer and craftsman. The qualities and interrelationships of forms may be so subtle and complex that they cannot be adequately specified and communicated to a craftsman. Moreover, many aspects of the design may actually be contributed during the process of working. Michelangelo’s way of working, for example, enabled him to change his mind about important aspects of composition as the work proceeded.

A complete fusion of design and craftsmanship may not be possible if a project is a large one or if the sculptor is unable to do all of the work him- or herself. The sheer physical labour of making a large sculpture can be considerable, and sculptors from Phidias in the 5th century bce to Henry Moore in the 20th century, for example, have employed pupils and assistants to help with it. Usually the sculptor delegates the time-consuming first stages of the work or some of its less important parts to his or her assistants and executes the final stages or the most important parts him- or herself.

On occasion, a sculptor may function like an architect or industrial designer. He or she may do no direct work at all on the finished sculpture, his or her contribution being to supply exhaustive specifications in the form of drawings and perhaps scale models for a work that is to be entirely fabricated by craftsmen. Obviously, such a procedure excludes the possibility of direct, personal expression through the handling of the materials; thus, works of this kind usually have the same anonymous, impersonal quality as architecture and industrial design. An impersonal approach to sculpture was favoured by many sculptors of the 1960s such as William Tucker, Donald Judd, and William Turnbull. They used the skilled anonymous workmanship of industrial fabrications to make their large-scale, extremely precise, simple sculptural forms that are called “primary structures.”