Stone Carving is the reduction of a block of stone to a finished state using a variety of tools. Procedures of carving processes can be used to create masonry for construction or for decorative purposes or both combined. Stone Carving has evolved slowly; many of the same techniques have been used for millennia. The recent trend to modernization of tools, the use of air guns, computer controlled cutters etc., cannot yet improve upon works finished by hand. Anyone able to swing a hammer and hold a chisel at the same time can attempt to carve. The tools required to start are relatively inexpensive and few, and yet to obtain a complete array of tools to run a full size workshop would cost several hundreds of dollars.
The stone used is a wide in variety, from igneous to sedimentary, hard to exceptionally soft. The most common stones carved are granite, sandstone, marble, and limestone. Others such as basalt, soapstone, alabaster are also occasionally carved. With certain stone care must be taken not to breathe the resulting dust, especially sandstone and granite which releases silicates that destroy lung tissue. Other stones may contain other dangerous minerals such as asbestos, for example Tigers Eye.
The choice of stone is predicated upon the necessity of durability, weatherability, color, availability, cost and ease of carving.
The most basic tools required are a hammer and chisel.
Hammers come in a variety of shapes weights and sizes and are generally described in units of ounces. The masons hammer has a rectangular flat faced head and a relatively short shaft compared to a framing hammer used in common carpentry. For strong application of energy the face is used, in order to use the mass effectively to transfer smaller amounts of energy the side of the hammer head is used. By adjusting the degree of force the amount of material removed in a single stroke can be modified. The greater the force the larger the amount of material removed and the greater the chance the block will react poorly and split in unforeseen ways. Hammers come in a variety of weights from a few ounces to several pounds. The heavier they are the better for mass removal whereas the lighter are better for fine control. Hammers also are obtainable in two standard materials, iron and hardened steel. The hardened steel is for general use on any stone. An iron headed hammer is somewhat softer and is meant for marble which often has a higher fragility so the extra shock absorbation reduces the risk of shattering the stone. Mallets are another variety of hammer that are a specialized group that have larger heads that are made out of wood (general a fruit wood like apple which has extremely strong and close grain) or synthetics. There are two basic styles of mallet, French and English. The French mallet consists of a round drum which the shaft passes through the center of the diameter of the drums altitude. The English mallet is the drum is perpendicular to the shaft. The French mallet is preferable to the English in that it allows finer adjustments in the transfer of energy and is more forgiving when not swung correctly at the chisel base. French mallets are most effective when the chisel is struck with the widest part of the drum which is closer to the shaft.
The chisel is obtainable in a wide variety of sizes and shapes for various functions. The major classes of chisels are for use with hammers, or air guns, and mallets.. The two classes of chisel are differentiated by their ends one having a flat surface and the other having a bulb. A chisel intended for a mallet must never be hit with a hammer as the bulb that receives the energy will bloom or flatten out this will then damage the head of the mallet.
Chisels can further be divided into several other categories. There are chisels intended for various classes of stones. There is one type of chisel especially for marble differentiated by the appearance of a head that has a neck that narrows perceptibly and then widens to the diameter of the shaft. The purpose is to allow sufficient recoil from the blows so that the stone does not simply explode. For harder stones chisels expand straight from the head to base in order to provide more mass to absorb the shock. Chisels must be properly tempered to retain a sharp edge. A sharp chisel is an absolutely necessity. A dull chisel will chatter, producing uneven results and also increase the tendency of the chisel to pluck large chunks from the stone being worked. There are several distinct forms of chisels. They are flat, forked, bullnose, semi circular gouge, point, and blunt. The flat chisel is for finish work. The forked chisel can be used to remove larger amounts of material and can be used to create patterned surfaces. This particular chisel was introduced around the 13th century, being the latest introduction in the chisel family. The bullnose is used to carve convex surfaces. The semi-circular gouge also used for making convex surfaces but of a more complex form. The point is used for breaking large amounts of material away. The blunt is used immediately after a point to reduce the remaining large masses.
Finally the most important tool for transferring the drawing to the block is the scribe. A very narrow pen-like pointed chisel that is has a hardened tip made of tool steel. This device is used by simply running it along the lines drawn on the block in pencil. Never use pens as the inks may bleed into the stone marring the color of the finished product. Weird but true.
Saws, drills, riffles, French drags, sandpaper, ruler, square, calipers, dividers, French curve, compass
Saws come in a variety of types. Circular saws are generally powered pneumatically or electrically the blades of which are impregnated with diamond chips or dust. There are chainsaws that are also specially designed to use diamond coated blades. Regular crosscut saws are used for sawing soft stones and are recognizable by their enormous teeth and elevated handle which allows the entire blade to sink through a block with out becoming obstructed by the handle. For use with limestone and other soft stone they are a worthwhile investment.
Drills in period were star shaped, hence the name, star-drill. To use you strike forcibly rotate, strike again rotate, until the desired depth is achieved. Modern drills dispense with this monotony and are easier to maintain. Carbide tips and diamond tip bits being readily available for the driver of choice.
Riffles are basically a type of file that is used for stone. The teeth are widely spaced and raised up higher than a normal file. They are used to get into tight spaces and to finish surfaces. They should be used minimally the chief work being accomplished by the chisel which is a vastly less expensive tool.
French drags are somewhat the equivalent of the plane in carpentry. They are used for soft stones and consist of blades set at alternating angles, between 15 and 30 degrees, over the length of a block of wood. The blades are toothed to provide even removal of surface material. Some drags can be fitted with specially shaped blades to follow convex surfaces. It is important to always run a drag towards the center of a block and never out across an edge. These tools are especially useful for final preparation of large surfaces.
Sandpaper comes in a variety of grits and is useful for adjusting the degree of polish on the final surface. Marble in particular benefits from such treatment and it is possible to obtain widely different polishes on a single block that can help differentiate flesh from fabric or other indicated surfaces.
The remaining tools while all esentially drafting tools are desirable to have more heavily built and therefore durable tools for use with stone carving. The square, ruler, divider, caliper, compass, and French curve are all used for either measuring an extant piece or laying out the drawing on a block prior to carving.
Drawing is oddly enough one of the most important skills that one can have for carving. In order to create any really well made sculpture, which adheres to stylistic principles of a genre, one must be able to draw. This skill is useful to visualize patterns in order to guide the carving process so that you may avoid getting lost in the stone and producing something that is a naive and uninformed effort. Drawing also enables one an inexpensive method of exploring how to proceed before making an insurmountable error. Additionally it sharpens the eye and forces the mind to translate from a three dimensional space to a two dimensional space which is useful since frequently the reverse is true when first working a block. Many of the tools used for drawing are listed as tools also for carving since they can be used to transfer the drawings onto the block directly. Templates, made of paper, plastic, or any conveniently shapeable flat material that may be used over an extended period of time, may be used to reproduce portions of a drawing on a block, or, in the case of replication, several blocks or even faces of the same block. This transfer is accomplished by the use of the stylus. It is not a good thing to use a pen or pencil on the stone as it will leaves stains and like as not destroy your writing implement as well.