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Marble sculpture is the art of creating three-dimensional forms from marble. Sculpture is among the oldest of the arts. Even before painting cave walls, early humans fashioned shapes from stone. From these beginnings, artefacts have evolved to their current complexity. The point at which they became art is for the beholder to decide.

Material origin and qualities



Main article: Marble


Marble is a metamorphic rock derived from limestone, composed mostly of calcite (a crystalline form of calcium carbonate, CaCO3). The original source of the parent limestone is the seabed deposition calcium carbonate in the form of microscopic animal skeletons or similar materials. Marble is formed when the limestone is transformed by heat and pressure after being overlain by other materials. The finest marbles for sculpture have no or few stains (some natural stain can be seen in the sculpture shown at left, which the sculptor has skillfully incorporated into the sculpture).

Advantages

Among the commonly available stones only marble has a slight surface translucency that is comparable to that of human skin. It is this translucency that gives a marble sculpture a visual depth beyond its surface and this evokes a certain realism when used for figurative works. Marble also has the advantage that when first quarried it is relatively soft and easy to work, refine, and polish. As the finished marble ages it becomes harder and more durable. Preference to the cheaper and less translucent limestone is based largely on the fineness of marble's grain, which enables the sculptor to render minute detail in a manner not always possible with limestone; it is also more weather resistant.

Disadvantages

The West Wind


Marble does not bear handling well as it will absorb skin oils when touched, which leads to yellow to brownish staining. While more resistant than limestone it is subject to attack by weak acids, and so performs poorly in outdoor environments subject to acid rain. For severe environments, granite is a more lasting material but one which is far more difficult to work and much less suitable for refined works such as those shown here.

Compared to metals such as bronze, marble lacks ductility and strength, requiring special structural considerations when planning a sculpture. In the sculpture shown to the right, the figure can be placed upon slender lower legs and the balls of the feet only because the bending stress in the sculpture is taken through the flowing drapery of the skirt, which is founded upon an upthrust portion of the ground and with the feet forms a tripod-like foundation for the mass. For comparison see some of the examples in the article concerning bronze sculpture (especially the sculpture Jeté) for the ease with which action and extension may be expressed.






Developing a sculpture

Sculptures may be developed directly from a marble block, although work performed on commission (such as a monumental portrait) will typically go through a process of development, approval, and refinement before stone is cut. This is achieved by a multi-step process, portions of which are suitable for the development of either a bronze, stone, concrete, or ceramic final product.

  • A large sculpture will often be developed first as a small maquette in wax or oil- or water-based clay, over an armature. This allows quick arrangement of massing, outlines, and poses.
  • The macquette will be enlarged by one or more steps (perhaps using a measuring frame) to the final size, usually using water-based clay, with fine details included.
  • From the finished clay master, a mold is developed, which may be waste mold, to be used only once, or a piece mold, capable of producing multiple copies.
  • Using the mold a rough plaster is created. Alternatively the final enlargement may be done in direct plaster.
  • The mold marks are removed from the plaster and additional refinements added, smoothing surfaces and adding details.


If a bronze is to be created, the plaster will be sent to an art foundry for the creation of a final mold (typically a synthetic rubber mould supported by plaster) and production of one or more wax copies for use in lost wax casting.Alternatively, the plaster may be bronzed, painted and waxed to appear as bronze, or used to produce a final piece mold for production of a terra-cotta or stoneware product, in turn glazed, painted, or bronzed to produce a final product or study proposal.

  • Working on the plaster, tacks are embedded at key reference points, projecting a small distance from the surface.
  • Using a three dimensional measuring frame surrounding the plaster the positions of the tacks are transferred to the raw marble block (using another frame) by a process called pointing, where conical holes are created in the block to the exact depth indicated by the reference tack on the plaster. The plaster may be enlarged to the marble by this process by multiplying the measurements by a constant scaling factor.
  • The conical holes are used as a guide to form a rough marble, possessing the final shape but without fine details or final surface textures.
  • Using the plaster as a visual guide, details are added and the final surface textures are produced.


Tools

The Italian terms for the basic carving tools of stone sculpture are given here, and where possible the English terms have been included.

  • La Mazza - The mallet. This is used to strike the chisel.
  • Gli Scalpelli - The chisels. These come in various types:
    • La Subbia - (the Point) a pointed chisel or punch
    • L'Unghietto - (Round or Rondel Chisel) Literally, "little fingernail"
    • La Gradina - (Toothed Chisel or Claw) a chisel with multiple teeth
    • Lo Scalpello - a flat chisel
  • Lo Scapezzatore - (Pitcher or Pitching Tool) a hefty chisel with a broad blunt edge, for splitting.
  • Il Martello Pneumatico - Pneumatic hammer
  • Il Flessibile - an angle grinder, fitted with an electrolysis-applied diamond studded blade
  • Hand Drill
In addition to those hand tools listed above, the marble sculptor would use a variety of hammers - both for the striking of edge tools (chisels and hand drills) and for striking the stone directly (Bocciarda a Martello in Italian, Boucharde in French, Bush Hammer in English). Following the work of the hammer and chisel, the sculptor will sometimes refine the form further through the use of Rasps, Files and Abrasive Rubbing Stones and/or Sandpaper to smooth the surface contours of the form.To achieve a high-lustre polish on marble a very fine abrasive, tin oxide, is used following the use of pumice or finer grits of sandpaper.

Tool technique



Hammer and point work is the technique used in working stone, in use at least since Roman times, as it is described in the legend of Pygmalion, and even earlier, the ancient Greek sculptors used it from c. 650 BC. It consists of holding the pointed chisel against the stone and swinging the hammer at it as hard as possible. When the hammer connects with the striking end of the chisel, its energy is transferred down the length and concentrates on a single point on the surface of the block, breaking the stone. This is continued in a line following the desired contour. It may sound simple but many months are required to attain competency. A good stone worker can maintain a rhythm of relatively longer blows (about one per second), swinging the hammer in a wider arc, lifting the chisel between blows to flick out any chips that remain in the way, and repositioning it for the next blow. This way, one can drive the point deeper into the stone and remove more material at a time. Some stoneworkers also spin the subbia in their fingers between hammer blows, thus applying with each blow a different part of the point to the stone. This helps prevent the point from breaking.

See also



A few well known marble sculptures





References

External links




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