There are two basic approaches to carving. The first is to find a
stone with a distinctive shape or color pattern that suggests
sculptural forms. This approach frees the carver to follow the
natural forms within the material. The qualities of the stone itself
become a major influence in determining the direction of the
The second approach is to begin by working out an idea for the sculpture in drawings or by modeling a maquette in clay or other easily worked material. Modeling in clay first, when you can add and subtract material, push and twist the forms around, and try different form combinations, frees the carver to develop the sculptural idea without worrying about taking off a chunk of stone that, as ideas change, he might later wish to have back.
Out: Before you begin carving, look at the
stone to determine the direction of the bed, or grain (similar to
wood). In sedimentary, metamorphic, and to a lesser extent, igneous
stone, the stone was formed by the accumulation of roughly parallel
layers of material built up over time. Wetting a sedimentary or
metamorphic stone with water will help display these bed lines,
often appearing as distinctive color patterns.
Stone will tend to break more easily when split along these bed lines, like opening the pages of a book. And, like trying to tear a phone book, it is more difficult to break (or tear), and breaks less predictably when the direction is perpendicular to the bed lines.
As in laying out a design for a wood carving, with stone you must also consider the direction of the grain to ensure the structural integrity of the parts of the carving. Try to keep the grain running with the length of the design, and avoid thin projections that protrude parallel to the grain.
Once you have determined the direction of the bed, check to see if there are any hair-line cracks in the stone that could open up and break off later during carving.
Now begin drawing your design on all sides of the stone. Make sure to project the same height and width of each form on to the other sides of the stone.
out: The quickest way to remove a
lot of stone form a block is with the pitching tool. To use
this tool, the stone must have a flat surface and squared corners.
Place the pitching tool about 1 1/2" from the edge of the stone.
Hold it straight up and down, then tilt it back slightly so that the
force is directed towards the area you want to break off. With
one sharp blow, break off the edge.|
After removing as much material as possible with the pitching tool, begin to define the shapes with the point chisel.
Hold the chisel with your thumb on the outside. It feels awkward at first, but prevents accidentally striking your thumb with the hammer.
Start carving by cutting parallel rows about an inch apart in the stone, creating ridges and grooves. Hold the chisel at an angle that just bites into the stone, but not so steeply that it will bury the tool. Try not to direct the chisel too deeply into the stone, which will result in pulverizing the stone directly under the point and producing a white blemish, or 'stone bruise.' These white marks require a lot of additional work to remove.
Now go back over the same area with a cross-hatch pattern of cuts to knock off the ridges of the first cuts. Place the point so it catches under the ridge and the force pops the chip off.
Using this technique, begin defining the geometric planes of the large forms.
Work all areas of the sculpture simultaneously so that the entire carving is always at the same stage of completion. In this manner you can make more accurate visual judgments about proceeding.
|A 4 1/2" diamond blade on a grinder can speed up the removal of stone.|| Make a series of
parallel cuts about 1" apart. Then break them off with the point
||All of the hand-carving chisel shapes, the
point, tooth, flat, and rondel, are also made to work with
pneumatic hammers. |
The pneumatic hammer's multiple-strokes-per-second saves time and reduces some of the physical work of carving. Its smooth action can cut a more flowing line through the softer stones.
The pneumatic hammer's rapid fire action, when used with bushing chisels (4 point, 9 point, and cup chisel), make it a very effective tool for shaping the harder stones like granite.
Pneumatic hammers come in different size from the large 1 1/4" hammer for roughing out, to the 1/2", or smaller, for fine detail work. The air pressure to the tool can also be increased for more power or reduced for finer control.
Forms: Once the large forms have been
established with the point chisel, begin refining them with a
tooth chisel. The point chisel has left a rough texture of grooves
and ridges which can be smoothed down with the tooth chisel.
The tooth chisel closely follows the contours of the forms. Hold the chisel at about a 45 degree angle. A higher angle only bruises the stone; a lower angle just skips over the surface. As with the point, try to catch the tool under a ridge of stone to pop it off.
| A flat
chisel is now used on flat or convex forms to remove the
texture left by the tooth chisel. Use the curved edge of the rondel
to clean out concave shapes.
During this cleaning up stage, you will discover if you have bruised the stone and need to do extra work to remove the white marks.
||Finishing: On the softer
stones, rasps and rifflers are used for the final
smoothing and shaping of the carving. The coarse teeth of a cabinet
maker's rasp or round rasp, when used in long sweeping strokes,
produces graceful flowing forms. |
On harder stones, a flat chisel is used to remove the ridges left by the tooth chisel.
The 9 point bushing chisel can be used on granite to smooth the surface. A diamond cup wheel on a mini grinder will remove the rough surface left by the bushing tools.
|| The smaller
rifflers with their varied shapes can get into small areas or
complex shapes. On the softer stones, much of the detail carving can
be done with rifflers. |
Final smoothing is done with wet/dry silicon carbide sand paper.
Polishing brings out the beautiful color and pattern of a stone.
With the softer stones, continue hand sanding with the wet/dry sand
paper under running water. Work through the grits (by roughly
doubling the number of the last grit) from 150 grit to your desired
degree of polish (somewhere between 600 to 3,000 grit).
On the harder stones, I use a pneumatic grinder with a center water feed and diamond pads in an assortment of grits from 40 to 3,000.
After you are finished thoroughly going over the piece with a particular grit, let the stone dry. Check to see if there are any scratches or other imperfections that were not removed by the last grit. Mark the blemishes with a colored pencil and go over the area again with the last grit until all the blemishes are removed before proceeding to the next finer grit.
If you have gone through all the grits, but did not stop and dry the stone to check for scratches, at the end you may be shocked to find scratches left in the otherwise beautiful finish. You have to start all over again from the beginning.