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Not to be confused with petroglyph or sculpture
The Kilmartin Stones in Scotland - a collection of ancient stone carved graveslabs Khazneh structure carved into a cliff in Petra southern JordanStone carving is an activity where pieces of rough natural stone are shaped by the controlled removal of stone. Owing to the permanence of the material, stone work has survived which was created during our prehistory or past time.
Work carried out by paleolithic societies to create stone tools is more often referred to as knapping. Stone carving that is done to produce lettering is more often referred to as lettering. The process of removing stone from the earth is called mining or quarrying.
Stone carving is one of the processes which may be used by an artist when creating a sculpture. The term also refers to the activity of masons in dressing stone blocks for use in architecture, building or civil engineering. It is also a phrase used by archaeologists, historians, and anthropologists to describe the activity involved in making some types of petroglyphs.
History
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The earliest known works of representational art are stone carvings. Often marks carved into rock or petroglyphs will survive where painted work will not. Prehistoric Venus figurines such as the Venus of Berekhat Ram may be as old as 250,000 years[citation needed], and are carved in stones such as tuff and limestone.
These earliest examples of the stone carving are the result of hitting or scratching a softer stone with a harder one, although sometimes more resilient materials such as antlers are known to have been used for relatively soft stone. Another early technique was to use an abrasive that was rubbed on the stone to remove the unwanted area. Prior to the discovery of steel by any culture, all stone carving was carried out by using an abrasion technique, following rough hewing of the stone block using hammers. The reason for this is that bronze, the hardest available metal until steel, is not hard enough to work any but the softest stone. The Ancient Greeks used the ductility of bronze to trap small granules of carborundum, that are naturally occurring on the island of Milos, thus making a very efficient file for abrading the stone.
The development of iron made possible stone carving tools, such as chisels, drills and saws made from steel, that were capable of being hardened and tempered to a state hard enough to cut stone without deforming, while not being so brittle as to shatter. Carving tools have changed little since then.
Modern, industrial, large quantity techniques still rely heavily on abrasion to cut and remove stone, although at a significantly faster rate with processes such as water erosion and diamond saw cutting.
One modern stone carving technique uses a new process: The technique of applying sudden high temperature to the surface. The expansion of the top surface due to the sudden increase in temperature causes it to break away. On a small scale, Oxy-acetylene torches are used. On an industrial scale, lasers are used. On a massive scale, carvings such as the Crazy Horse Memorial carved from the Harney Peak granite of Mount Rushmore and the Confederate Memorial Park in Albany, Georgia are produced using jet heat torches.
Stone sculpture
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Carving stone into sculpture is an activity older than civilization itself. Prehistoric sculptures were usually human forms, such as the Venus of Willendorf and the faceless statues of the Cycladic cultures. Later cultures devised animal, human-animal and abstract forms in stone. The earliest cultures used abrasive techniques, and modern technology employs pneumatic hammers and other devices. But for most of human history, sculptors used hammer and chisel as the basic tools for carving stone.
The process begins with the selection of a stone for carving. Some artists use the stone itself as inspiration; the Renaissance artist Michelangelo claimed that his job was to free the human form trapped inside the block. Other artists begin with a form already in mind and find a stone to complement their vision. The sculptor may begin by forming a model in clay or wax, sketching the form of the statue on paper or drawing a general outline of the statue on the stone itself.
When ready to carve, the artist usually begins by knocking off large portions of unwanted stone. This is the "roughing out" stage of the sculpting process. For this task they may select a point chisel, which is a long, hefty piece of steel with a point at one end and a broad striking surface at the other. A pitching tool may also be used at this early stage; which is a wedge-shaped chisel with a broad, flat edge. The pitching tool is useful for splitting the stone and removing large, unwanted chunks. Those two chisels are used in combination with a masons driving hammer.
Once the general shape of the statue has been determined, the sculptor uses other tools to refine the figure. A toothed chisel or claw chisel has multiple gouging surfaces which create parallel lines in the stone. These tools are generally used to add texture to the figure. An artist might mark out specific lines by using calipers to measure an area of stone to be addressed, and marking the removal area with pencil, charcoal or chalk. The stone carver generally uses a shallower stroke at this point in the process, usually in combination with a wooden mallet.
Eventually the sculptor has changed the stone from a rough block into the general shape of the finished statue. Tools called rasps and rifflers are then used to enhance the shape into its final form. A rasp is a flat, steel tool with a coarse surface. The sculptor uses broad, sweeping strokes to remove excess stone as small chips or dust. A riffler is a smaller variation of the rasp, which can be used to create details such as folds of clothing or locks of hair.
The final stage of the carving process is polishing. Sandpaper can be used as a first step in the polishing process, or sand cloth. Emery, a stone that is harder and rougher than the sculpture media, is also used in the finishing process. This abrading, or wearing away, brings out the color of the stone, reveals patterns in the surface and adds a sheen. Tin and iron oxides are often used to give the stone a highly reflective exterior.
Sculptures can be carved via either the direct or the indirect carving method. Indirect carving is a way of carving by using an accurate clay, wax or plaster model, which is then copied with the use of a compass or proportional dividers[1] or a pointing machine. The direct carving method is a way of carving in a more intuitive way, without first making an elaborate model. Sometimes a sketch on paper or a rough clay draft is made.
Stone carving considerations
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'Arabic' style carving on ashlar building blocks, Beith , Scotland
Stone has been used for carving since ancient times for many reasons. Most types of stone are easier to find than metal ores, which have to be mined and smelted. Stone can be dug from the surface and carved with hand tools. Stone is more durable than wood, and carvings in stone last much longer than wooden artifacts. Stone comes in many varieties and artists have abundant choices in color, quality and relative hardness.
Soft stone such as chalk, soapstone, pumice and Tufa can be easily carved with found items such as harder stone or in the case of chalk even the fingernail. Limestones and marbles can be worked using abrasives and simple iron tools. Granite, basalt and some metamorphic stone is difficult to carve even with iron or steel tools; usually tungsten carbide tipped tools are used, although abrasives still work well. Modern techniques often use abrasives attached to machine tools to cut the stone.
Precious and semi-precious gemstones are also carved into delicate shapes for jewellery or larger items, and polished; this is sometimes referred to as lapidary, although strictly speaking lapidary refers to cutting and polishing alone.
When worked, some stones release dust that can damage lungs (silica crystals are usually to blame), so a respirator is sometimes needed.
Basic stone carving tools fall into five categories:
More advanced processes, such as laser cutting and jet torches, use sudden high temperature with a combination of cooling water to spall flakes of stone. Other modern processes may involve diamond-wire machines or other large scale production equipment to remove large sections of undesired stone.
The use of chisels for stone carving is possible in several ways. Two are:
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There are many types and styles of stone carving tools, each carver will decide for themselves which tools to use. Traditionalists might use hand tools only.
Powered pneumatic hammers make the hard work easier. Progress on shaping stone is faster with pneumatic carving tools. Air hammers (such as Cuturi) place many thousands of impacts per minute upon the end of the tool, which would usually be manufactured or modified to suit the purpose. This type of tool creates the ability to 'shave' the stone, providing a smooth and consistent stroke, allowing for larger surfaces to be worked.
Among modern tool types, there are two main stone carving chisels:
Gallery
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See also
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References
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Man has been creating art from stone ever since he found he could shape it by striking a softer stone with a harder one. Over the millennia, a few types of stone have become popular with sculptors. Here are the most common ones used for carving from the three different types of rock: igneous, sedimentary, and metamorphic.
Igneous: The characteristics of igneous rocks result from the way in which they were formed. Deep in the earth, under the intense heat of volcanic action, magma was forced up through the older solid rock. It then cooled, forming granite, basalt, and diorite. Granite is made of quartz crystals and feldspar which contain silica. Prolonged breathing of silica can cause lung damage. Wear a good respirator when around granite dust.
Graniteis a very hard stone and difficult to carve. In fact 'carving' might not be the right word, since you are not pushing the chisel through the material like you would with the limestone or marble, but are pulverizing the stone, trying to break off chips of crystals (which can be as sharp as glass).
Your carving tools must be carbide-tipped to stand up to the wear and tear of working granite. Fine detailed carving is better left to other types of stone.
Diamond saws and cup grinders cut through granite quite easily and can speed up the carving and finishing process. Granite comes in a wide variety of colors, and the crystal size can vary from large and coarse to very fine and dense. Granite takes a high polish and holds up very well outdoors.
Sedimentary: As rocks began to erode from wind, rain, and sun, the particles were washed into low lying areas where the sediment accumulated.
In the sea, small plant and animal forms died and drifted to the bottom, adding to the sediment. Over thousands of years, the pressure of these layers cemented the sediment onto limestone or sandstone.
Limestone formed on the sea floor from sediment and the bodies of primitive sea creatures. As you are working, you can find small fossilized creatures like crynoids and brachiopods in the stone. Limestone is composed primarily of the mineral calcite, or calcium carbonate.
Limestone is easy to carve and will hold small detail work, but is also strong enough to support undercutting. While it does not have the innate beauty of the more colorful stones, a wide variety of textures can be created that can really bring the stone to life. There is a definite 'grain' or bed (formed as the layers of sediment stacked upon each other on the sea floor) in limestone.
The stone breaks fairly predictably along the bed lines, but less cooperatively going across the bed. (Think of opening a book with the pages, compared to trying to tear it across the pages.) Limestone can be polished, but the polish will not last long outdoors. Limestone seems to survive acid rain better than marble, so is a good choice for outdoor sculpture.
Sandstone is formed from sedimentary sand held together by silica or calcium carbonate. Sandstone also has a distinct bed direction, and large chips can be broken off when going with the bed. Sandstone tends to wear out your tools quickly. Sandstone contains silica, so a respirator must be worn.
Metamorphic: Metamorphic rocks are formed when a sedimentary layer is exposed to heat and pressure and undergoes a chemical change which forms a new crystalline material. After metamorphism, limestone becomes marble.
Marble has been the most preferred stone for carving since the time of the ancient Greeks. Marble is moderately hard to work. It will hold very fine detail. Marbles from the United States comes in over 250 colors. When brought to a high polish, its crystalline structure sparkles. It does not hold up well outdoors. Acid rain begins to deteriorate the surface within a few years.
Alabaster is a very soft stone for carving and tends to flake and split along hidden cracks in the stone. It will take a high polish, which brings out its incredible colors and patterns. In fact the stone is so beautiful that the viewer may overlook your sculptural forms and only admire the stone. The dust from alabaster may cause an allergic reaction in some people, so wear a respirator.
Soapstone, or steatite, is soft enough to carve with a knife. It is composed of talc and has a slippery, soapy feel. It will take a polish and hold fine texture detail. It is a good choice for your first stone carving. Prolonged exposure to talc dust can cause respiratory problems, so wear a respirator.
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