Science Fair Project Encyclopedia
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Stone carving is an ancient activity. Owing to the permanence of the material, evidence can be found that even the earliest cultures indulged in some form of stone work. Carving stone differs from quarrying stone in that it is the act of shaping or incising the stone, whereas quarrying is the activity of acquiring useful stone, usually in blocks, from geological sources.
The term stone carving is of particular signifigance to sculptors being a reference to a particular way of producing sculpture, as opposed to modelling in clay or casting. The term also refers to the activity of masons in dressing stone blocks for use in Architecture, Building or Civil Engineering. It is is also a phrase used by archaeologists, historians, and anthropologists to describe the activity involved in making petroglyphs.
Stone Carving History
The earliest examples of 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.
In Ancient Greece all stone carving was carried out using this abrasion technique, following rough hewing of the stone block using hammers. The reason for this is that the Ancient Greeks were a bronze age culture and bronze is not tough enough to work most resilient stone. The Ancient Greeks used bronze to trap small granules of naturally occurring carborundum thus making a very efficient file for abrading the stone.
The development of Iron as a material co-incided with the Romans and Hellenic and Ptolomaic greeks. stone carving tools made from iron were developed that were capable of being hardened, these tools have changed little since then.
Stone Carving considerations
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 most metamorphic stone is difficult to carve even with iron tools, usually tungsten tipped tools are used, although abrasives still work well. modern techniques often use abrasives attached to machine tools to cut the stone, in rare instances heat is used such as at the huge carving on a mountain at Mount Rushmore in the US. where small jet engines were used to provide the heat.
Precious and semi-precious stones 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.
Stone Carving Tools
Basic stone carving tools fall into 3 types
- Percussion tools - to hit with.
- such as mallets, axes, adzes, bouchards and toothed hammers.
- chisels - to cut with
- such as lettering chisels, points, Pitching tools, and claw chisels.
- Abrasives - to erode with
- such as carborundum blocks, drills, saws, grinding and cutting wheels, water erosion machinery and dressing tools such as french and english drags.
The use of chisels for stone carving is possible in two ways
- The masons stroke
- where a flat chisel is used at approximately 90 degrees to the surface in an organised sweep. It shatters the stone beneath it and each successive pass lowers the surface.
- The Lettering stroke
- where the chisel is used along the surface at approximately 30 degrees to cut beneath the existing surface.
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