Pointing machine
Encyclopedia
Stone sculpture
Stone sculpture is the result of forming 3-dimensional visually interesting objects from stone.Carving stone into sculpture is an activity older than civilization itself, beginning perhaps with incised images on cave walls. Prehistoric sculptures were usually human forms, such as the Venus of...
and woodcarvers
Wood carving
Wood carving is a form of working wood by means of a cutting tool in one hand or a chisel by two hands or with one hand on a chisel and one hand on a mallet, resulting in a wooden figure or figurine, or in the sculptural ornamentation of a wooden object...
to accurately copy
Copying
Copying is the duplication of information or an artifact based only on an instance of that information or artifact, and not using the process that originally generated it. With analog forms of information, copying is only possible to a limited degree of accuracy, which depends on the quality of the...
plaster
Plaster
Plaster is a building material used for coating walls and ceilings. Plaster starts as a dry powder similar to mortar or cement and like those materials it is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after setting,...
, clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
or wax
Wax
thumb|right|[[Cetyl palmitate]], a typical wax ester.Wax refers to a class of chemical compounds that are plastic near ambient temperatures. Characteristically, they melt above 45 °C to give a low viscosity liquid. Waxes are insoluble in water but soluble in organic, nonpolar solvents...
sculpture
Sculpture
Sculpture is three-dimensional artwork created by shaping or combining hard materials—typically stone such as marble—or metal, glass, or wood. Softer materials can also be used, such as clay, textiles, plastics, polymers and softer metals...
models
Prototype
A prototype is an early sample or model built to test a concept or process or to act as a thing to be replicated or learned from.The word prototype derives from the Greek πρωτότυπον , "primitive form", neutral of πρωτότυπος , "original, primitive", from πρῶτος , "first" and τύπος ,...
into wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
or stone
Dimension stone
Dimension stone is natural stone or rock that has been selected and fabricated to specific sizes or shapes. Color, texture and pattern, and surface finish of the stone are also normal requirements...
.
The device is a contraption of brass
Brass
Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...
or stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....
rod
Rod (geometry)
In geometry, a rod is a three-dimensional, solid cylinder....
s and joint
Kinematic pair
A kinematic pair is a connection between two bodies that imposes constraints on their relative movement. Franz Reuleaux introduced the kinematic pair as a new approach to the study of machines that provided an advance over the notion of elements consisting of simple machines.Hartenberg & Denavit...
s, which can be placed into any position and then tightened. It is not actually a machine; its name is derived from the Italian macchinetta di punta.
This tool was first invented by the French sculptor and medallist Nicolas-Marie Gatteaux
Nicolas-Marie Gatteaux
Nicolas-Marie Gatteaux was a French medal engraver, also notable as the father of the sculptor and medallist Jacques-Édouard Gatteaux...
(1751–1832) and "perfected" by Canova
Antonio Canova
Antonio Canova was an Italian sculptor from the Republic of Venice who became famous for his marble sculptures that delicately rendered nude flesh...
.
Use
The pointing machine is used for making one-to-one copies of existing sculptures and to execute models from plasterPlaster
Plaster is a building material used for coating walls and ceilings. Plaster starts as a dry powder similar to mortar or cement and like those materials it is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after setting,...
, modeling clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
or modeling wax
Wax
thumb|right|[[Cetyl palmitate]], a typical wax ester.Wax refers to a class of chemical compounds that are plastic near ambient temperatures. Characteristically, they melt above 45 °C to give a low viscosity liquid. Waxes are insoluble in water but soluble in organic, nonpolar solvents...
in materials like stone or wood, on the same scale. Enlarged or reduced scale sculptures are not possible via this method (for this a set of calipers or a three-dimensional version of the pantograph was used).
To better control the end result of the finished sculpture, sculptors have increasingly taken to making a detailed model, and then reproducing this on the same scale or enlarged this in stone. Especially in the 19th century, sculptors would work along very specific methods: first a wax or clay model was made, of which a plaster cast was taken, which in its turn served as the model to be copied in stone, with the use of calipers or a pointing machine. This is called the indirect method of carving.
The advantages of this method are that the end result is very controllable and that the chance of making irreparable mistakes is reduced drastically. In addition, the process is much faster when carving difficult sculptures, because the search for the right shape is done during the modelling process instead of during the carving itself, thus making it much easier to adjust it or make changes. Finally, using this method, much of the work or all of it can be done by assistant sculptors, increasing the productivity. The disadvantage of using the pointing machine is a great loss of directness and the chance of loss of expression.
Gradually, famous sculptors would more and more tend to use assistants. Sometimes a sculptor would run a large workshop with dozens of assistants and pupils. Art academies were formed where the skills of sculpture were taught in detail. The consequence of this development was the generation of a kind of 'academy art', from which some sculptors wanted to distance themselves. Sculptors eventually returned to more direct forms of expression, by means of for example the 'direct carving method', impressionism
Impressionism
Impressionism was a 19th-century art movement that originated with a group of Paris-based artists whose independent exhibitions brought them to prominence during the 1870s and 1880s...
and expressionism
Expressionism
Expressionism was a modernist movement, initially in poetry and painting, originating in Germany at the beginning of the 20th century. Its typical trait is to present the world solely from a subjective perspective, distorting it radically for emotional effect in order to evoke moods or ideas...
, sometimes influenced by the indigenous art of Africa
African art
African art constitutes one of the most diverse legacies on earth. Though many casual observers tend to generalize "traditional" African art, the continent is full of people, societies, and civilizations, each with a unique visual special culture. The definition also includes the art of the African...
and Oceania
Art of Oceania
Oceanic art refers to the creative works made by the native peoples of the Pacific Islands and Australia, including areas as far apart as Hawaii and Easter Island. Specifically it refers to the works of the two groups of people that settled the area, though during two different periods. They...
, that brought about a shock because of its directness and raw expression. Because of this, the pointing machine was used less and less, also because the knowledge and the skills of carving in wood and stone were rapidly getting lost during the 20th century.
Technique
To transfer measuring points from a model to a block of stone or wood, the sculptor usually takes three reference points on both model and block, from which to start. By using three of these points, a sculpture can be measured accurately, for the three directions of measuring are hereby defined (width, height and depth). These three measuring points are traditionally used by sculptors to copy a sculpture with caliperCaliper
A caliper is a device used to measure the distance between two opposing sides of an object. A caliper can be as simple as a compass with inward or outward-facing points...
s, but this is was simplified significantly with the invention
Invention
An invention is a novel composition, device, or process. An invention may be derived from a pre-existing model or idea, or it could be independently conceived, in which case it may be a radical breakthrough. In addition, there is cultural invention, which is an innovative set of useful social...
of the pointing machine.
On these basic points, a (usually wooden) T-shaped support is mounted, the cross. On this crosswood, the actual pointing device is attached. By then moving the arms of the tool in such a way that the point of the needle just touches the point to be measured on the model, for instance the nose of a bust
Bust (sculpture)
A bust is a sculpted or cast representation of the upper part of the human figure, depicting a person's head and neck, as well as a variable portion of the chest and shoulders. The piece is normally supported by a plinth. These forms recreate the likeness of an individual...
, the sculptor sets the device.
Next he takes the whole cross, pointing machine and all, to the block of stone or wood and hooks it up in the identical, corresponding basic points.
The needle that defines the measuring point can slide. By subsequently carving or drilling carefully until the needle touches the stop, the sculptor can place his measuring point exactly in the block.
By thus copying several dozens or hundreds of points, an accurate copy
Copying
Copying is the duplication of information or an artifact based only on an instance of that information or artifact, and not using the process that originally generated it. With analog forms of information, copying is only possible to a limited degree of accuracy, which depends on the quality of the...
can be carved. The end result however will still depend on the skill of the sculptor, because these points are only the basis.
The real advantage is the need to measure each point only once, instead of three times with callipers (height, width and depth). Also there is no need to read scales
Linear scale
A linear scale, also called a bar scale, scale bar, graphic scale, or graphical scale, is a means of visually showing the scale of a map, nautical chart, engineering drawing, or architectural drawing....
in inch
Inch
An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...
es or centimetre
Centimetre
A centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the SI base unit of length. Centi is the SI prefix for a factor of . Hence a centimetre can be written as or — meaning or respectively...
s, and consequently much less room for error.
Usually, the sculptor will make his own crosswood for the statue
Statue
A statue is a sculpture in the round representing a person or persons, an animal, an idea or an event, normally full-length, as opposed to a bust, and at least close to life-size, or larger...
, as a small statue obviously will need a much smaller one than a life-size one.
History and future
Before the invention of the pointing machine by Gatteaux, sculptors used several methods to measure and copy sculpture, such as gridsRegular grid
A regular grid is a tessellation of n-dimensional Euclidean space by congruent parallelotopes . Grids of this type appear on graph paper and may be used in finite element analysis as well as finite volume methods and finite difference methods...
, which were already in use in early Egyptian sculpture, measuring sticks and calipers. The main technique was to measure the model from three fixed points with calipers.
Nowadays pointing machines are available in laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
versions as well. These have the advantage that the needle is not hindering the carving, and that the sculptor hears an audio-signal to warn him when the right depth is reached.
The latest developments are computer guided
Computer-aided manufacturing
Computer-aided manufacturing is the use of computer software to control machine tools and related machinery in the manufacturing of workpieces. This is not the only definition for CAM, but it is the most common; CAM may also refer to the use of a computer to assist in all operations of a...
router
CNC Router
A Computer Numerical Controlled router is a computer controlled machine for composites, aluminum, steel, plastics, wood and foams. It is a specific version of a CNCtool....
systems that scan
3D scanner
A 3D scanner is a device that analyzes a real-world object or environment to collect data on its shape and possibly its appearance . The collected data can then be used to construct digital, three dimensional models....
a model
Scale model
A scale model is a physical model, a representation or copy of an object that is larger or smaller than the actual size of the object, which seeks to maintain the relative proportions of the physical size of the original object. Very often the scale model is used as a guide to making the object in...
and can produce it in a variety of materials and in any desired size.