Wood Carving Techniques
Wood can be accurately shaped into complex forms by an amount of effort well within the capacity of the human hand using an edged steel tool. The end of a small, flat bar is ground to an angle of about 60° and then honed on a hard, fine-grained stone to a degree of sharpness that is microscopic. Shavings of wood may be removed by pushing the edge of this tool, called a chisel, against the block, at the same time sliding it laterally. Larger quantities of wood may be removed by driving the opposite (handle) end of the chisel with a mallet. Less efficient techniques were used by wood-carvers before the discovery of steel.
The edge of the tool may be curved in various arcs, in which case it is called a gouge. The edge may make a 60° or 90° angle to the tool's length. Very narrow-angled or curved tools are called veiners. Since the heavier cutting is first done by the gouge, and the chisel is then used largely to reduce the furrows to a smooth plane, carvers sometimes call the straight chisel a firmer, and it may be ground somewhat differently from the carpenter's chisel. The shanks of gouges and chisels may be given a variety of splayed ("fishtail") and bent shapes for access to interior planes or to shape small planes efficiently in one stroke, and the width of the edge may vary from 8th of an inch up to 2 inches. An assortment of sizes in all available shank shapes could expand a wood-carver's collection of tools to a very high number, but a serviceable range can be made up of one or two dozen items.
Files and rasps in a range of shapes and degrees of fineness are used for smoothing the surface of the wood preparatory to the final sanding, although some artists prefer the more animated quality of the tooled surface. Some finishers recommend burnishing the surface with a harder piece of wood or with the standard burnishing tools (steel, agate, and so on) used throughout the crafts. A final finish may be applied in any of the well-known transparent substances such as shellac, varnish, oil, and wax (with or without preliminary use of a stain) or the work may be painted with opaque substances, concealing the grain and applying a color scheme that is naturalistic or otherwise independent of the limited natural color range of wood. When this type of polychrome surface is to be used, fine sanding and other polishing techniques are generally omitted, and a prime coat with some body like gesso (fine plaster) is applied for smoothness.
The fibrovascular structure of wood brings about certain conditions that must be taken into account by the carver. The cutting tool moves most readily in a direction generally paralleling that of the fibers ("with the grain"), but care must be taken not to split the wood. This precaution is less necessary with denser, close-grained woods, more necessary with lighter, open-grained woods. Projections should be made in a direction coinciding as closely as possible with the grain of the wood, as "short grain" is weak. That is to say, a piece of wood with the grain running at right angles to its length is apt to split off under pressure. For this reason it is necessary to design figures in wood somewhat massively, without too much articulation. The problem also may be overcome by carving different parts of the figure as an arm, a leg, and so on from different pieces of wood, with the grain in the right direction for each. Skilled techniques are required for assembling such figures; otherwise a generous amount of gesso must be used to conceal the joinings.
Trees grow only to a certain size, and a block may not be the full diameter of the trunk since it is inadvisable to use heartwood (the center of the log). This is because of excessive checking or cracking in that area from the tensions set up by shrinkage as the wood dries. Therefore, the scale of wood sculpture is limited; but there are ways of extending it somewhat. Planks can be "glued up" into sizable blocks. Jointing may be employed as described. Large compositions may be made by assembling a number of individually carved figures against a constructed background. In rare instances very large figures have been constructed on a wood framework with a planked surface.
Unlike metal and ceramic products, facsimiles of which may be produced by various casting techniques, a carving is unique. However, there are machines which can reproduce rapidly and simultaneously from a master pattern a number of simple pieces such as furniture details (the foot of a bureau or the arm of a chair), small objects such as smoking pipes, and even uncomplicated sculptural figures. These work either on the principle of the router (for flat panels or relief carving) or on that of the lathe (for three-dimensional pieces), with a series of tools cutting into a series of blanks until a controlling finger comes in contact with the surface of the master pattern. Elaborate shapes and undercutting cannot be accomplished in this manner, but the pieces produced by the "gang carver" generally are finished with varying amounts of hand tooling proportionate to the prospective price of the object.