Tools and Machinery of the Granite Industry, Part III
Wood, Paul
Granite Finishing
A small number of basic finished dimension stones made up the great majority of granite shed production. For gravestones and private monuments, there were dies (the main stone on which the lettering and ornamentation was cut), bottom bases, second bases, markers (a small stone set either flush to or raised from the ground level), posts (indicating the corners of a cemetery plot), boulders (natural-shaped stones, usually rock face finished), tablets (a die whose lower portion is buried underground), crosses, shafts, and columns. For mausoleums and vaults, there were roof stones and sidewall stones. For buildings and large public monuments, there were ashlars (four- to twelve-inch thick blocks that were carefully dressed on top, bottom, and sides so they could be set in a wall with uniform and tight joints), columns, capitals, steps, foundations, bas-relief panels, and statuary. The finished surfaces applied to these stones were rock face-an irregular natural looking surface produced by chipping out pieces of stone with a chisel; hammered-a powdered or steeled surface produced by hand or pneumatic bush hammer and of varying degrees of smoothness; polished-a mirror-like finish produced by a polishing machine; and carved-a wide variety of surface shapes and textures produced by hand tools, by a small pneumatic carving tool, or by sandblasting.
The finishing of granite involves only two basic processes-shattering and abrasion. Shattering is the crushing and breaking of granite by the impact of a steel tool. The bull set, hand set, hand point, chisel, circular saw, surfacing machine, cutting lathe, and the first two stages of polishing machine use are examples of tools and machines that work by shattering. Abrasion is the wearing away of granite by an abrasive forced under pressure along the stone’s surface. The gang saw, wire saw, Carborundum saw, grinding machine, polishing lathe, and the last stage of polishing machine use are examples of tools and machines that work by abrasion. Sandblasting appears to employ a combination of the two processes.
Much of the progress in granite finishing can be credited to advancements in abrasive technology. Natural abrasive materials were used from ancient times, including beach sand, whetstone dust, red limestone powder (Tripoli), emery powder, tin oxide putty, garnet dust, and iron filings. In the latter part of the nineteenth century, manufactured abrasives began to appear, including flint shot, cast iron shot, chilled cast iron shot, broken iron shot, chilled steel shot (Figure 1), broken steel shot, and emery bricks. During the twentieth century, artificially synthesized abrasive materials entered the market, including artificial diamonds, silicon carbide, aluminum oxide, boron carbide, cubic boron nitride, cerium oxide, tungsten carbide, and contained abrasive bricks. Contained abrasive bricks are molded blocks of abrasive contained in a binding-matrix material such as magnesite and chloride. They are used for the initial stages of polishing and are more economical to use than loose abrasives.
Evolution of Shed Architecture
Many farmers harvested granite boulders from their fields and shaped the stone during the winter slow time in unused spaces in a barn or shed. The earliest commercial stone sheds were designed around the boom derrick-either a round shed with a centrally located inside derrick that could reach any point in the shed or a horseshoe-shaped shed that defined a semi-circular yard with an outside derrick that could reach all the shed doors and any point in the yard (Figure 2). The final form was the straight shed having a rectangular footprint and designed for an inside overhead traveling bridge crane (Figure 3). One or two cranes could run along tracks that ran the full length of the shed and by this means reach any point in the shed. Whereas granite quarries were typically located at higher hilltop elevations where much of the overburden had been glacially removed, granite sheds were usually located in the valleys, often in an existing town, where worker housing and water or electric power were available.
Granite sheds needed to be provided with a variety of supporting services such as compressed air, water, heat, light, and dust removal. Compressed air was usually supplied via 4-inch diameter threaded iron pipes that went down both sides of the shed. Each pipe had a smaller-diameter steam pipe inside to warm the air and lower its relative humidity to prevent freeze up of pneumatic tool exhaust ports. Heating also yielded an added quantity of compressed air at a lower cost compared to that produced by a compressor. Smaller feeder hoses went to each granite cutter’s or carver’s workstation- called a banker-and surfacing machines with a shutoff valve for each (Figure 4). Water pipes, with either well or cityprovided water, went down both sides of the shed. The horizontal and vertical grinders required large quantities of water to keep the dust down. Considerable water was also used in the tool grinding room.
Steam from boilers or exhaust steam from steam engines was piped to a heat exchanger. Fans blew air over the heat exchanger steam pipes and into a system of ducts that distributed hot air throughout the shed. On cloudy days or late winter days, the windows did not provide adequate lighting and electric lights were required. Lighting was provided by a row of large wattage light bulbs with porcelain reflectors. They were spaced at regular intervals down the center of the shed, hung under the roof ridgeline.
Before the installation of suction dust removal equipment, most granite cutting sheds had louvered cupolas along the roof ridgeline that were designed to vent airborne stone dust to the outside (Figure 3). Crane operators could open or close the vents by hanging rope-operated, hinged doors. Considering the amount of airborne dust generated, these vents did little to alleviate the dust problem. After the installation of section equipment, the vent doors were always kept closed to conserve heat. For dust removal by suction, the dust laden air passed through a system of overhead ducts that exhausted into dust collectors/filter s located outside the shed. State law required that the suction equipment to be periodically checked with a vacuum gauge.
Each granite company had a shed whistle operated by compressed air that was typically located on the boiler room roof. It blew four times a day: start of workday, start of lunch, end of lunch, and end of workday. All the shed whistles in a granite town took part in a wave of whistle blasts; each whistle had its own distinctive tone and was slightly out of sync with the others.
Unloading the Quarry Blocks
Although today quarry saw blocks arrive on flatbed trucks, in the past they arrived at the cutting shed on railroad flatcars and were unloaded by a yard boom derrick located near the spur track. The block might be loaded onto a transfer car that was pulled into the shed on a standard gauge railroad spur track. (A transfer car is illustrated in Figure 19). Then, an overhead crane would transfer the block to a saw car that was winched into the gang saw on its own dedicated track. Or, the yard derrick might load the block directly onto a saw car if the saw car track extended outside the shed.
Large, multi-shed cutting plant operations required an efficient, high-capacity, materials handling facility, especially for building granite for which a single contract might involve thousands of pieces of finished granite. Often, this was provided by a large, rectangular runway or stone yard serviced by one or more overhead traveling bridge cranes, under which ran multiple railroad spur tracks (Figure 5). This arrangement allowed many flatcars and transfer cars to be simultaneously unloaded and loaded.
Sawing
The ancient Egyptians used a copper-bladed, stone saw with sand abrasive. An early form of handsaw used in the American granite industry had a 2-foot long, 3/16-inch thick iron blade with square teeth. It had an ordinary saw handle and a knob handle at the opposite end of the blade. Often there was an abrasive shot reservoir on top. One use for this saw was cutting grooves between individual reeds (thin parallel strips resembling reeds) on a large monument. In his book, Stone Working Machinery, M. Powis Bale notes that the Collis family, owners of a large marble quarry and early-eighteenth-century stone-working pioneers in Kilkenny, Ireland, employed gang saws that had twelve soft iron blades. The saws used sand and water abrasive and could saw ten to twelve inches per day, doing the work of about twenty hand sawyers. The blade frame was driven by a water-powered crank and pitman rod.
The gang saw was the first stop for stone from the quarry (Figure 6). The objective of sawing is to cut the quarry saw block into slabs ranging from a few inches to a foot or more in thickness. A typical saw block was 10 feet by 5 feet by 5 feet. In 1909, the Woodbury Granite Co. at Hardwick, Vermont, had two gang saws-one accommodating a maximum stone size of 10 feet by 8 feet by 6 feet and the other a maximum stone size of 16 feet by 6 feet by 7 feet. The hard way (one of the 5-foot by 10-foot faces) was marked at the quarry so the stone could be oriented in the saw such that the cuts were made along the plane of the hard way. Hence, the faces of the slabs produced by the saw were along the hard way plane and would become the faces of monuments. The close grain of the hard way results in the most beautiful finished surface-polished or hammered. The gang saw consisted of a reciprocating frame with multiple cutting blades driven by a crank and pitman rod. The pitman rod was a long wooden shaft that transmitted poser from the crank to the blade frame (Figure 6). The name was derived from the pitman that powered the timbercutting down stroke of a pit saw. The main framework was initially wood and later iron. The saw used six or so steel blades 16 inches high and 16 feet long. The saw blade cutting edges had 2-inch-wide by 4-inch-deep rectangular notches spaced about 6 inches apart (Figure 7). Gang saw blades evolved from smooth-edged to notched and finally to brazed-on diamond segments. The gang saw was a noisy machine-making dragging and screeching sounds that could be heard a mile or more from the shed. They usually ran twenty-four hours a day with two-man crews.
The saw blades were tightened in the blade frame with wedges at the blade ends. Proper tension would be indicated by the ring of the blade when struck by the wooden handle of a shovel. Following cut marks made by the foreman on the saw block, blade spacing was set by placing wooden gauges between the blades. For example, eight blades spaced eight inches apart could yield seven 8-inch thick, 10-foot by 5-foot slabs from a 10-foot by 5-foot by 5-foot saw block. The saw block was positioned under the blades on a saw car that was secured by wooden blocks during sawing (Figure 8). The saw car tracks, which ran under each saw, were typically forty-five-pound rails laid seven to eight feet wide. In 1857, Andrews Merriman of Chicago, Illinois, patented (no. 24,478) a gang saw feed mechanism with four motor-driven dogged screws which forced the saw frame onto the stone through rigid hanging rods connected to the four corners of the frame. This greatly increased the sawing rate. The saw used abrasive steel shot stored in a tank above the saw. The abrasive was mixed with water and poured down onto the saw blades. The shot eventually fell into a pit under the saw and was recycled back up to the tank. If the blades started steaming, more shot was required. After sawing was complete, each slab was separated, chained, laid down and acid washed to prevent rust staining from the iron shot. Normally, the slab front and back was hammered or polished prior to splitting into dimension pieces. Since the gang saw produced a very rough surface with saw marks, a hammered surface was applied by a surfacing machine prior to polishing. After sawing and polishing or hammering, defects were often discovered that were not apparent on the exterior surface of the quarry saw block. For monumental work, this often resulted in the rejection of one or more slabs. The manufacturer and quarry owner usually came to a financial agreement-typically sharing in the loss.
Initially, gang saws used hand-shoveled, sand abrasive. The introduction of abrasive elevators and cleaners for gang saws greatly increased the sawing rate. There were a dozen patents issued in the 1880s for abrasive (sand and water) feed mechanisms for stone sawing just to inventors in the Rutland, Vermont, area. At this time there were three Rutland manufacturers of gang saws (Lincoln Iron Works, Mansfield & Stimson Foundry, and F. R. Patch Manufacturing Co.) that were supplying the local marble industry. The water and sand (or chilled metal shot) abrasive mixture was lifted and mixed by means of a force pump. The pump used in abrasive feeds was a difficult problem due to the rapid wear out of the pump caused by the highly destructive nature of the abrasive being pumped. The common piston-type pump was not viable due to the need for constant repair and replacement of parts. Diaphragm pumps, the same design as previously described for quarry pumping, and centrifugal pumps were able to pump abrasives with very little wear and were used for most abrasive pumping applications. An abrasive distributor was introduced to feed abrasive to multiple gang saws so that one man could tend a dozen saws instead of just two.
Sand was adequate for soft stones such as marble, but for granite the use of chilled metal shot was required. In the mid 1870s, Struthers & Sons of Philadelphia was manufacturing 1/40-to-inch to 1/50-inch chilled iron shot for gang saws under a Tilghman patent. Chilling, the rapid cooling of the iron shot, hardened it and lengthened its abrasive life. Large granite blocks could now be sawn at the rate of three to four inches per hour and small blocks at twelve to fourteen inches per hour. (Using sand, the rate was about one inch per hour.) Three pounds of shot were consumed for every square foot of stone sawed. About 1885, John Harrison of Canada started his experiments with iron and steel shot abrasives. He later moved to England to be close to the sources of iron and began large-scale manufacture of abrasive shot widely used in the granite industry.
In the late 1940s and early 1950s, the wire saw replaced the gang saw for granite sawing (Figure 9). The wire cut faster, produced a narrower kerf- thus wasting less stone-and was quieter in operation. The wire saw might use a loop of single strand, multiple strand, twisted ribbon, or embedded diamond wire, but usually a two-strand twisted wire having a cross-section width of a quarter inch and a reverse twist every twenty-five to fifty feet was used (Figure 10). The wire loop moved at sixty miles per hour and a suspended weight of five to six hundred pounds maintained a constant tension in the loop. An automated down feed mechanism forced the wire down onto the stone and accelerated the cut. A flow of tungsten carbide abrasive was maintained into the cut by an abrasive pump. Joseph and John Dessureau of Barre, Vermont, one of the principal manufacturers of wire saws, were issued three patents for wire sawing: (1) improvements in automatic down feed for wire saws (1954, no. 2,674,238); (2) a wire design which claimed to have a longer life, to cut at substantially the same rate over its lifetime, to be easier to twist, to retain its twisted shape, and to retain adequate tensile strength (1958, no. 2,856,914); and (3) a machine to twist sawing wire so that it would be straight, free from torsion and have a tight uniform pitch. It also described a new method of producing twist reversals (1965, no. 3,225,798).
The saw wire loop was often four thousand feet or more in length to prolong the life of the wire. The wire was supported on a series of thirty to sixty inch diameter sheaves running as much as a half mile from the shed. (Five sheaves are visible in Figure 9.) Otherwise, the wire would have had to be replaced too frequently and might wear out and break in the middle of a cut. For example, an eight hundred-foot loop would be worn out after approximately twelve hours of continuous sawing of an eight-foot-long cut. Typically, the wire had to be changed every day or every other day. The new wire was silver soldered to the old wire and pulled through the system of sheaves. Then, the new wire was silver soldered to itself-forming a loop. The saw operator was responsible for the wire replacement. A maintenance man was responsible for the maintenance and repair of the sheaves. Like gang saws, wire saws were run both day and night. An eight-wire saw was the primary saw for cutting saw blocks into slabs. The saw block was leaned against another block so that the slabs on that side would not fall over after having been cut. A chain from an overhead crane was attached to an eye in the floor to prevent slabs on the other side from falling over. An iron bar was used to tilt each slab, which was then slowly lowered by the crane and chain. Each block was then washed, numbered and stored.
The vertical contour saw was a specialized form of the wire saw, patented in 1958 by Joseph and John Dessureau (Figure 11). It had a short loop of vertically oriented wire driven by an electric motor, all of which was supported on a jointed framework attached to a shed post or wall. The framework allowed the operator to move the saw anywhere in a horizontal plane so that the vertical wire, like a jigsaw, could cut edges and holes of any shape or curvature. Cutting could also be directed by a template pattern. Abrasive was supplied to the wire by a pump that was located in the bottom of an abrasive sump pit. The operation of this saw was a dirty job-the emery abrasive flew off the spinning wheels onto the operator’s face and into his mouth and got into every nook of his clothing! Later versions of the contour saw used diamond embedded wire. Today, the computer-controlled, horizontal, diamond wire contour saw is used for sawing complex curves and holes-for example, the Echo diamond wire profiling machine and the Pelligrini diamond wire saw.
The wire saw was gradually replaced by the rotary saw which initially had a six-to seven-foot diameter saw blade with removable, steel teeth so that worn out teeth could be removed and new teeth riveted on in the machine shop (Figure 12). The saw cut a 7/8-inch kerf which was held open by wedges to prevent binding up of the blade. The height of the saw blade could be adjusted and could make up to a three-foot deep cut. The angle of the saw blade could be varied, enabling the saw to cut faces on slant markers, ridges on mausoleums, and obelisks. The stones to be sawed were carried on saw cars which ran on a track under the saw. An abrasive pump in a sump pit recirculated steel shot up into an abrasive hopper. From the hopper, the abrasive poured through pipe into the saw cut and streams of water ran onto both sides of the blade to wash the abrasive down to the saw teeth in the bottom of the cut (Figure 13). These saws were usually run twentyfour hours a day. The whine and screech of the rotary saw could be heard for some distance outside the plant.
As early as the 1860s, H. & J. L. Young of New York City designed and manufactured a circular saw with embedded diamonds. In the early 1890s, the French company M.M. d’Aspine Achard manufactured a circular saw with one-half-carat, rough, black diamonds ($5-$10 each) set in the circumference. Achard’s key contribution was a new setting technique in which the diamonds were retained even with the high blade edge speed-much higher than gang saw blades. The diamond saw yielded a very smooth sawn surface that could be polished without any intermediate dressing. It was estimated that the sawing rate was twenty to fifty times that of a gang saw using sand or iron shot. By the turn of the twentieth century, F. R. Patch Manufacturing Co. of Rutland, Vermont, was manufacturing a gantry diamond circular saw with a 300-pound, 6 ½-foot diameter blade that rotated at 500 rpm (Figure 14). The company touted its highly reliable diamond setting technique and promised only the best quality (hard) diamond borts. Now, computer-controlled circular saws with up to thirteen-foot diameter diamond segment edged blades carry out the large-scale initial sawing of the quarry saw blocks. The diamond segments are set onto the blade with a brazing technique. A twelve-foot diameter blade has about 160 diamond segments and can saw fifteen square feet per hour. The saw moves over a stationary saw block with a continuous flow of water on the blade for cooling, to reduce airborne dust and to flush out the cuttings. These saws run twenty-four hours per day, unattended during nights and weekends. The computer notifies the operator by telephone at home if there is any problem.
There are now available a wide variety of diamond saws, some hand-held and some supported on rails, arms, or gantries. Examples include horizontal saw, gantry saw, vertical curve saw, slab saw, radial arm saw, rail saw, chain saw, cut off saw, and band saw.
Lifting and Moving Granite Within and Between the Sheds
Although occasionally a boom derrick similar to those used in the quarry might be used inside a round shed, it was the straight shed with its overhead traveling bridge crane that revolutionized the lifting and movement of granite in the shed. The manually powered, overhead bridge crane with a chain fall hoist was introduced into the American granite industry in the 1880s, apparently having originated in Scotland. The overhead traveling bridge crane consisted of a bridge that spanned the width of the shed (thirty to forty feet) and ran on tracks that went the entire length of the shed-one track on each side of the shed. A trolley ran back and forth on tracks that went the length of the bridge. A fall rope and hook was suspended from the trolley and was raised and lowered by a hoist on the trolley. Thus, the hook could reach any location on the shed floor. The Lane Manufacturing Co. of Montpelier, Vermont, was one of the early manufacturers of traveling bridge cranes. Their initial design was a “flying rope” crane, powered by a continuously moving endless loop of hemp rope driven by a steam engine or electric motor (Figure 15). The rope loop ran the entire length of the shed on sheaves and also ran across the bridge to power the trolley. The operator sat on the trolley and controlled the crane through levers and foot pedals, looking down through a grating to see the hook and lumper. It is said that many a longtime crane operator had a bent neck from constantly looking down through the grating. A long loop of rope moving at high speed was quite dangerous. In one recorded case, the rope came offits sheaves and decapitated a worker! These cranes were soon replaced by electric cranes
The Lane Manufacturing Company’s electric, overhead bridge crane (ca. 1895) had two non-reversing electric motors, essentially replacing sheaves in the old flying rope design-one motor on the trolley to power the fall rope hoist and to move the trolley and one motor on the bridge to move the bridge (Figure 16). Lane also began to replace wooden parts with steel. Electricity was conveyed to the bridge by three bare conducting cables that ran the length of the shed rails and were continuously contacted by a set of three wheels on the bridge as it moved back and forth along the length of the shed. Electricity was conveyed from the bridge to the trolley by three bare conducting cables that ran the length of the bridge and were continuously contacted by a set of three wheels on the trolley as it moved back and forth along the bridge. Like the flying rope crane, the operator sat in the trolley. The operator had two wheels to control the hook and the trolley. The wheel on the left controlled the hoist and hook-turned one way the hook was raised, turned the other the hook was lowered, and in the center position the hook was stationary. There was a lever to the operator’s right that selected one of two hoist-operating speeds-high and low. The wheel on the right controlled the trolley-turned one way the trolley moved in one direction, turned the other way the trolley moved in the opposite direction, and in the center position the trolley was stationary. There were two brake pedals-the left one braked the hoist and the right one braked the trolley. The trolley and the hook could be moved simultaneously. Bridge movement was controlled by a rod that ran along on top of the bridge beam on the operator’s left side. If the rod was pulled one way the bridge moved in one direction, and if pulled the other way the bridge moved in the opposite direction, and if centered the bridge remained stationary.
Pawling & Harnischfeger of Milwaukee, Wisconsin, made the next major advance in traveling bridge cranes by the use of three motors-one for the bridge, one for the trolley, and one for the fall rope and hook. All the motors were direct connected and had variable-speed controllers allowing the clutches and “frictions” to be eliminated. This greatly simplified the design and led to greater reliability and less down time. In addition, P&H provided its cranes with operator cabs suspended under and at one end of the bridge, which allowed much better visibility for the operator. F. R. Patch Manufacturing Co. of Rutland, Vermont, manufactured a four-motor bridge crane. The fourth motor was for the fast lifting of light loads. This crane had a bridge speed of 200 to 300 feet per minute, a trolley speed of 100 to 150 feet per minute, and a hoisting speed of 12 to 30 feet per minute. Modern overhead bridge cranes have dispensed with an operator riding on the crane by providing hanging wire controls or hand-held radio controls so that an operator on the floor can both load and unload the hook as well as operate the crane.
Rollers, levers, lifting jacks, and block and tackle were used to move granite short distances in the shed. A chain fall hoist on an overhead track, a platform truck, a lift truck with skids, a two-wheel truck, or a roller dolly might also be used to move small loads over short distances. Also, conveyor systems with slab turners and monument turners were introduced as an efficient way of moving small to medium-size stones. In the early 1900s, stone-lifting tongs (or grabs) were introduced with lead-faced “safe feet” that could be used on finished stone without harming the surface (Figure 17). Roller and shackles with a canvas or nylon slings with capacities of five to eight tons (ca. late 1940s) and vacuum lifters were introduced as replacements for chains and wire cables to hitch the stone to the crane hook (Figure 18). They were both more convenient and were less likely to damage the stone. The larger granite cutting plants had their own railroad spur track network that ran both between and within the sheds. Standard flatcars as well as transfer cars (Figure 19), pulled by cable or pushed or pulled by a locomotive crane or small switching locomotive, were used to move granite between sheds.
Flat Surfacing
The bush hammer, a hammer for cutting and dressing stone, was invented and patented (patent without number) by Joseph Richards in 1828 (Figure 20). It was the first stone-working tool breakthrough in several centuries. The bush hammer (or ax hammer) had a set of removable blades (or cuts) on each side of the head-the greater the number of cuts the finer the dressing of the stone. The blades were held between two plates or cheeks by four bolts. The handle was also held in place between the plates. A number of additional hand tools have been used over time for manual surfacing including the peen hammer, hammer and point, scotia hammer, and hand bush chisel. To measure surface flatness, two pair of winding blocks were used (Figure 21). These 2 ½-inch high cast iron posts were placed on the granite block to be surfaced with a straight edge on top of each pair. The stonecutter sighted across the two straight edges. If the edges were parallel with each other, the stone was flat. If not, more stone was taken off until the edges became parallel. When the surface was flat, it was said to be “out of wind” (rhymes with “wind a clock.”) The plumb bob was also a key tool for the layout and aligning of granite blocks.
Alexander McDonald of Cambridge, Massachusetts, was issued an 1879 patent (no. 222,194) for the first successful stone-surfacing machine (Figure 22). It consisted of two stages-first a planer and then a bushing machine directly behind the planer. The first stage of the McDonald mechanical (non-pneumatic) surfacing machine used freely turning, eight-inch diameter-cutting discs. These discs were made of tempered steel with the working surface beveled to a sharp edge. The discs were mounted on two cutting heads, four to a head, which rotated at twenty to twenty-five rpm on vertical shafts. The heads were driven by a steam engine through a system of belts, pulleys and gears and required about eight horsepower. The stone moved on a driven carriage, at one to two inches per minute, under the cutters. About 150 square feet could be surfaced in one day. Blocks 18 feet long by 8 feet wide by 6 feet high could be accommodated. This massive machine required a space 26 feet high by 16 feet wide by 20 feet high. Only twelve of these twenty-eight-ton machines were ever built, at a cost of $8,000 each. The McDonald surfacers were usually housed outside the main sheds since they were noisy and dusty machines. Unfortunately, the operators must have had extreme exposure to granite dust.
Later, circa 1890, pneumatic surfacing machines were introduced that used a single, powerful pneumatic hammer either attached to the end of a sliding horizontal bar-bartype- or mounted on a trolley that moved along a fixed horizontal bar-crane-type-(Figure 23). (The pneumatic hammer will be described later in “Roughing Out and Cutting.”) The horizontal bar was supported by a vertical post which was mounted on a cart with wheels. The bar could be raised or lowered by a hand-cranked winch and could rotate around the post in a horizontal plane, allowing the operator to position the tool anywhere inside a circle up to twenty feet in diameter. Thus, the pneumatic surfacer could handle very large surfaces, larger than could be produced by the gang saw. Pneumatic surfacers cost about $3,500 each and were simpler and more reliable than the McDonald surfacing machine. James S. McCoy’s American Pneumatic Tool Co. was one of the early manufacturers and supplied the Charles H. More & Co. of Barre and Montpelier, Vermont, with two of the first pneumatic surfacers. These were used on granite for the Iowa State Soldier’s Monument, the largest monument of its type in 1894. The pneumatic surfacer used a four-point tooth chisel bit for the initial surfacing (Figure 24) and a nine-point tooth chisel bit or a bush chisel bit for the final surfacing (Figure 25). The surfacing machine bush chisel bit could have from four to ten blades-or cuts-of decreasing thickness; the more numerous and thinner the cuts the smoother the resulting surface. The bush chisel bit produced the following hammered surfaces: four-cut-suitable for steps, approaches, and upper building stories; six-cut-suitable for commercial and public buildings; eight-cut-suitable for memorials, mausoleums, building entrances, landscape art; and ten-cut-a velvety smooth surface suitable for monuments and statuary.
The surfacer’s pneumatic tool required seventy-five psi compressed air and could surface about sixty square feet in nine hours, which was equivalent to a saving of eighteen dollars per day, or fifty-four hundred per year, over manual surfacing. It was said this machine replaced twelve men with hand bush hammers. A gang-sawed surface could not be used as an exposed surface since it was scored with blade marks and therefore had to be smoothed with the pneumatic surfacing machine. Since pneumatic surfacers were prodigious generators of airborne granite dust, they were later supplied with water to wet the stone and keep down airborne dust. Often during warmer weather, they were moved outside to alleviate the dust problem. By the late 1930s, most pneumatic surfacing machines were equipped with surfacer dust collectors which removed the dust by suction (Figures 26 and 27). The dust collector suction nozzle was positioned near to and moved with the pneumatic tool bit so as to suck up the highest percentage of produced dust. The nozzle was connected to a chip trap and suction fan via a flexible duct, allowing free movement of the surfacer bar and pneumatic tool.
The hand-held pneumatic surfacing, bushing and rough chiseling tool, called the hand facer, or “Bumper,” was a heavy, powerful tool, weighing about eleven pounds and accommodating a large bit with a 1 ¼-inch diameter shank (Figure 28). The vibration of this tool was so severe that after a day’s use, the stonecutter’s hands became numb due to lack of circulation-an affliction called “dead fingers.” ‘The Bumper” was a major issue for the stonecutter’s union, and they succeeded in having it banned in many of their labor contracts. Today, some supply companies selling pneumatic tools offer shock absorbing (anti-vibration) leather gloves.
Polishing
The ancient method of flat surface polishing employed a weighted iron plate that was moved back and forth over a stone using a sequence of ever finer abrasives: sharp sand, then fine sand or whetstone dust, then Tripoli (red limestone dust), and finally tin oxide putty. The earliest polishing machines were manual and were only suitable for small jobs. One example of a manual polishing machine consisted of a 68-inch long arm with a polishing wheel and handle at one end. The other end of the arm was pivot-mounted on a roller mechanism that moved back and forth on a 6-foot long track. By grasping the handle, the operator could position the polishing wheel to reach any point on a horizontal plane. The polisher was manually powered by a crank handle geared to the wheel. The polisher came with three polishing wheels: a 6½-inch diameter cast iron wheel with four spiral grooves for initial grinding, a 4-inch-diameter cast iron wheel with a smooth surface for closing up, and a 6½-inch-diameter wood surface wheel for fastening a buffing cloth for final polishing.
By the early 1700s, the Collis family of Kilkenny, Ireland, was employing powered polishing machines. The stone to be polished was placed on a table and an iron plate with sand and then limestone dust was driven back and forth on top of the stone by a water-powered crank and pitman rod. For the final polish, a buffer with oxide putty was used. Medad and Prentiss Wright of Montpelier, Vermont, were issued an 1878 patent (no. 203, 234) for the first of a long line of successful gate-type polishing machine designs (Figure 29). This patent described the fundamental characteristics of a post- or wall-mounted polisher with an articulated gate-like arm that could move 36O degrees and reach two polishing beds.
The gate- or arm-type polisher consisted of a horizontally oriented, cast iron polishing wheel supported by an articulated arm that allowed the wheel to be moved, via an operator handle, to any position in a horizontal plane. The arm framework, which supported a system of pulleys and flat belts to drive the wheel, was attached to a shed post or wall and depending on size had a radial swing of from five to eleven feet. Most polishers had bevel gears at the top so that the driving belt could be horizontal. A pair of cone pulleys allowed several polishing wheel speeds. The framework and polishing wheel could be manually raised and lowered. Later designs included a powered mechanism to raise and lower the framework and wheel. This polisher was called the “Jenny Lind,” after the celebrated singer who toured the U.S. under the sponsorship of P. T. Barnum, because it emitted a pleasing humming sound. In 1896-97, H. H. Harvey of Boston was selling a “counterpoised” gatetype polisher for $125. By the mid-twentieth century, polishing machines were powered by an electric motor. One popular design had the polishing wheel at one end of a centrally supported arm that was belt driven by a counterbalancing electric motor at the other end of the arm (Figure 30).
Polishers were used on surfaces prepared by the gang saw and the surfacing machine. Polishing took place in three stages: initial grinding with sand or iron shot; closing up with emery or Carborundum; and buffing with tin or zinc oxide. Abrasive consumption for the three polishing stages would be approximately: ½a to 1 pound per square foot of no. 3 iron shot; ¼ pound per square foot of no. 80 Carborundum; and 1/40 pound per square foot of tin oxide. A variety of polishing wheels were used depending on the polishing stage and abrasive used: broken scroll, cast scroll, emery ring, concentric ring, contained abrasive brick, rope buffer, coco mat, and felt buffer (Figure 31). A typical 18-inch polishing wheel was designed to rotate at 200 rpm, required a 10 HP engine and, with an experienced operator, could polish thirty to forty square feet in an eight-hour day. Often the first-stage polishers had an abrasive pump that fed abrasive to the polishing wheel which allowed faster polishing so this machine could supply several other machines that were doing the closing up and buffing. During the last stage, buffing, the polishers used were first a very fine wheel and then a felt buffing wheel. The felt buffing wheel was a cast iron wheel with slots into which pieces of felt were inserted and wedged in place with wood pins.
Bed setters prepared multiple stones in a level bed so that they could be simultaneously polished by a large, gate-type polisher (Figure 32). (Polishing of an entire slab greatly simplified the setting process.) Bed setting required only relatively simple tools but did involve considerable skill and experience to do the job right. It was a dirty job and bed setters typically wore overalls. First, a stone was blocked with wooden blocks and wedges. A level was used in two perpendicular directions to insure a level surface. An iron pry bar was used to make the necessary adjustments. As additional stones were added, they were blocked and made level with the first stone and any other adjacent stones. A hatchet was used to drive wedges between the stones. Next, paper was stuffed into the cracks between the stones. Using a wooden paddle, the remaining cracks were filled with plaster level with the top of the stones. The plaster both helped to hold the stones in place and also to keep the abrasive on the surface and in action. Prior to final buffing, the top quarter inch of plaster was removed so it would not contaminate the buffer. Later designs of the gate-type polisher, for example those manufactured by W A. Lane Co. of Montpelier, Vermont, in the 1890s, included an arm that could reach two beds. Thus, while one bed was being polished, the other was being set up so that the polisher could be in continuous operation.
The vertical polishing machine manufactured by the Concord Axle Co. and used circa 1890, was suspended from an overhead beam (Figure 33). It had a ten- to twenty-foot-long vertical main shaft with bevel driving gears and a universal joint at its top. The polishing wheel was attached to the bottom of the shaft with a second universal joint. The shaft and polishing wheel could be raised and lowered and had a counterbalancing weight to make movement easy. This polisher had many degrees of freedom-the polishing wheel could be moved to any point on a horizontal plane and could be raised and lowered. The polishing wheel could also be tilted to any angle. This flexibility allowed the vertical polisher to work on curved as well as horizontal or slanted flat surfaces. In 1896-97, H. H. Harvey was selling a vertical polishing machine for $100.
The hand polisher was suspended from a chain fall hoist attached to a trolley that ran along the top of the swinging horizontal boom of a crane. The hoist allowed the operator to raise and lower the polisher. The polisher head was belt-driven from an electric motor mounted directly on the suspended polisher frame. The operator stood on a four- to five-foot high wooden platform and could move the polisher to reach two workstations. He could be polishing the sides and top of one die while a second was being set in place. The hand polisher was used to polish the sides of large dies, to polish curved surfaces or tight places, and to polish out scratches and nicks.
Granite polishers have evolved into very sophisticated computer-controlled multi-head polishers with contained abrasive blocks such as the French-made Thibaut twelve-head continuous polisher that automatically moves the granite from one polishing stage to the next and can polish two hundred square feet of granite per hour. One of the most complex and most capable automated granite-working machines, the Thibaut GB110, grinds, shapes, routs, drills, and polishes.
Splitting
Given a number of outstanding orders, the shed foreman would look for a slab of a certain thickness and granite type to fill some of the orders. After measuring with a rule, he would ticket the selected slab. Later, a lumper would come along and dig out the ticketed slab-sometimes having to move a half dozen slabs to get at it. The layout man, who was often also the shed foreman, following dimensions on the shop tickets, would then mark the cut lines on the slab with chalk in such a way to insure minimum waste. Then he and a helper, known as the breaker, would cut it using a slab splitter and striking hammer. For a very thick slab, it might be necessary to drill holes along the chalk lines and split the slab using wedges and shims. Later, when wire saws and diamond circular saws became available, they were used to make these cuts. Today, the hydraulic slab splitter (“hydrosplitter”) is used for this job. It consists of a bed on which the slab rests and a pair of hydraulically powered knives, one positioned above and the other below the slab. The enormous forces (20,000 psi) applied to the slab by the knives splits the stone in a fraction of a second.
Roughing Out and Cutting
Stonecutters were usually the most numerous of the granite workers in a shed. Each stonecutter worked at a banker-a bench consisting of saw horses or wooden blocks to support the stone being worked on. Normally, the stonecutter stood as he worked, with his whole body involved in the work. Occasionally, a neighboring stonecutter might help (Figure 34), and for a really large stone, two or more stonecutters might work at the same banker. Each banker was supplied with compressed air through a hose with various couplings connected to the stonecutter’s pneumatic hammer. A banker might also be supplied with water, and by the late 1930s, had a suction device, called the banker dust collector, for the removal of airborne granite dust (Figure 35). Carvers also worked at bankers and, although fewer in number, usually worked side-by-side with the stonecutters.
After a stone had been sawn, flat surfaced, polished, and rough split, the stonecutter roughed out, trimmed, and finished the stone using a variety of hand and pneumatic tools. The stonecutter worked from a diagram or “shop ticket,” which included a working drawing of the finished piece along with dimensions and finishing information (Figure 36). The shop ticket had a three-dimensional (isometric) drawing of the die, base, and marker, and gave its overall dimensions (height, width, and depth) in feet and inches. Defining dimensions were given for such shapes as serpentine or oval tops, scotias, checks, chamfers, margins, etc. Finishes were specified for each surface such as polished, rock-aced, steeled, planed, honed, or wire-sawed. Often the finish was also indicated graphically-for example, parallel lines for polished surfaces and arcs for rock faced surfaces.
To guide the roughing out, trimming and finishing, the stonecutter laid out the lines and surfaces on the stone from the working drawing using a straight edge, carpenter’s square, stonecutter’s chalk and chalk line, and African marking camwood, a tropical wood used like chalk to mark granite surfaces. For monumental work, the stonecutter did not usually work to fine tolerances, but his flat cut surfaces had to be uniform and without obvious waves or irregularities and his angles “eye true.” However, for fine mausoleum and building work, tolerances of 1/32 inch, and sometimes even 1/64 inch, were often maintained so that the blocks and ashlars would fit together with tight seams. This degree of accuracy required machine finishing.
First the stonecutter, with the help of a neighboring cutter, would rough shape the stone with a bull set. Next, the hand tracer was used to trace the chalk-marked lines along which the stone would be trimmed. A two- to three-pound steel hand hammer was used to strike the hand tools. The die front and back were used to square up the sides, top and bottom. Then, a hand set or heavy-duty offset hand set was used to trim the stone to size along the traced lines (Figure 37). This was followed by the hand chipper to crisp edges of the stone (Figure 38). A straight edge, up to eight feet long, with lead plugs so as not to damage the finished surface might have been clamped onto the stone along the edge to guide the chipping process. Or, as in Figure 34, a coworker might have held a straight edge. Next, a hand point or hand chisel was used for knocking off high points on the sides and top (Figure 39). Finally, a hand bush chisel or bush hammer was used to smooth the surface and close the grain. The stonecutter often prepared the stone for the carver-for example, removing and finishing the background around a to-be-carved bas-relief. If the stonecutter had sufficient skill, he might use a chisel to cut rock face (or rock pitch) surfaces, or this might be done later by a carver. Used with restraint, rock face surfaces can add a natural dignity to a monument. The simple rugged broken surface can stand in contrast to a hammered or polished surface (Figure 40). Many consider that rock face work imparts the feeling of natural stone, the ruggedness of granite, and a rough and rustic beauty. Tool marks are considered undesirable in rock face work, but these often can be removed later by spelling the granite with an acetylene torch.
The first practical hand-held pneumatic hammer (weighing about fifteen pounds) was designed and patented (1885, no. 323,053) by James S. McCoy of Brooklyn, New York, (Figure 41) based on a smaller dental tool designed by Samuel W. Dennis and patented by him in 1878 (no. 205,169). The hammer operated on 40 psi compressed air that was alternately directed to the back and front of a piston by a transverse annular value and achieved several thousand strokes per minute. The pneumatic hammer piston impacted a removable tool (or bit) that was held in a spring-retracted tool holder. The pneumatic hammer produced an almost continuous sequence of impacts, allowing a rapid removal of a large quantity of granite during roughing out and producing a very smooth granite surface during finishing. McCoy patented a number of improvements as he experimented with different designs-testimony to the difficulty in designing a really practical pneumatic hammer.
The big breakthrough in pneumatic hammers was the valve-less design, which was first patented by Herman Kotten of New York City in 1898 (patent no. 605,486) but probably invented earlier around 1883 by Thomas Dallett of Philadelphia, Pennsylvania, who never patented his designs. Dallett protected his market by continuous design improvements and by a solid reputation for high quality. Later patents by Samuel Oldham of Philadelphia, Pennsylvania (1898, no. 609,162,), and William Holden of Barre, Vermont (1902, no. 711,859), claimed various improvements. The valve-less pneumatic hammer design resulted in a highly reliable tool with only one moving part-the piston (Figure 42). An elaborate, and usually patented, system of ducts and ports in both the piston and the cylinder wall was employed to alternately direct the compressed air to the front and back of the piston. As it moved, the piston itself opened and closed the input and exhaust air ports to drive the piston back and forth; the movement of the piston itself acted as a valve. The front of the piston narrowed into a neck-like hammer, which extended into an airtight bushing. The front of the bushing accepted the tool shank, which was struck by the piston hammer from two to four thousand times per minute. The manufactures of pneumatic hammers made many claims-longest wearing, smoothest running, quickest action, least friction, most sparing use of compressed air, and best control of the force of the hammer blow. Each of the major manufacturers (Dallett, Kotten, Oldham, and Trow & Holden) seemed to have had its loyal following of users. In the early 1900s, these small pneumatic hammers cost about $200 each.
Usually, the stonecutter had three sizes of pneumatic hammers: large (1-inch-diameter piston) for initial roughing out, large raised letters, and heavy carving; medium (¾-inch-diameter piston); and small (½-inch-diameter piston) for fine work such as sunk letters and tracing and for carving and finish work (Figures 43 and 44). The pneumatic hammer had many different tool bits that performed functions similar to the hand tools. In fact, some manufacturers offered a detachable striking cap that fitted over the shank of a pneumatic hammer tool bit so that it could be struck with a hand hammer. The point bit was used to rough out stone and knock off high places. The ripper bit was used for fast removal of stone in hard-to-reach places. The cape chisel bit was used for crisping lines, joining corners, detailing, or splitting. The four-point tooth chisel bit was used for fast, aggressive roughing out and the nine-point tooth chisel bit was used after the four-point to make a more uniform surface. The double-blade chisel bit might be used after the four- or nine-point tooth chisel to smooth the surface and take off high points. The three-blade bush chisel bit, smoother than the double blade, leaves an axed or brushed surface. The bush chisel bit, a finishing tool, was used to close the grain. The criss-cross chisel bit might have been used after the nine-point or three-blade chisel and leaves a unique cross-hatched finish. The cup chisel bit, a bushing tool, closed the surface and leaves a unique texture (Figure 45).
Grinding
The horizontal grinder was a contour grinder designed especially for curved surfaces such as serpentine, oval or beveled tops. It used a ten- to twelve-inch diameter cylinder-shaped Carborundum wheel with a horizontal arbor. The wheel moved over the top of the stone with the curved side of the wheel doing the grinding. The stone was placed on a hydraulically operated car on rails that moved the stone under the Carborundum wheel; the wheel arbor was stationary. The height of the car was determined by following an iron template to produce the desired contour. There were a number of standard template designs for serpentine, oval and beveled tops. If a customer wanted a non-standard contour, a stonecutter was needed to cut this by hand, guided by a draftsman’s drawing.
The molding grinder was used to cut scotias, rabbets, moldings, and the like. The Carborundum wheels varied in size, for example ½ inch wide by 24 inch diameter or 2 inch wide by 24 inch diameter. The shape of the cutting surface had a shape that matched the shape to be cut. For planing, a wide wheel was used-for example 6 inch wide by 24 inch diameter. The grinding wheel was mounted on a head whose height was adjusted by the operator. The granite block moved back and forth under the grinding head on a car driven by a linear gear. The length of travel was set by the operator according to the size of the stone. Hand-held Carborundum disc grinders were also used for hard to reach spots and for final touch up.
The vertical grinder was specially designed to grind the straight edges of mausoleum roofs or side stones up to twelve to fourteen feet square. The grinder had a vertically oriented, five-foot diameter iron wheel (with horizontal arbor) faced with Carborundum bricks. The stone was brought in on rollers and wedged into place. The face of the grinding wheel moved over the side of the stone and had a thirty-foot traverse.
Lettering and Shape Carving
Lettering could be cut by a stonecutter but was usually done by a granite worker who specialized in letter cutting, especially when raised letters were needed. There are four basic types of hand cut lettering; V-sunk (Figure 40) or round sunk; round or square raised; raised rustic (e.g., letters formed by vines or branches); and frosted or polished with outline (see figure in sidebar, page 134). For V-sunk lettering, the letters were cut into a hammered or polished flat surface producing the V-shaped grooves that formed the letters. The best V-sunk work has deep cuts and sharp well-defined edges and bottom. For raised lettering, all the stone on the surface around the letters was cut away leaving the raised letters projecting above the surface. Great care had to be taken to avoid chipping off a piece of the raised letters. The best raised work had a uniform half round profile for the round raised letters and clean sharp edges for the square raised letters.
In the early days of stone lettering, a stonecutter simply cut freehand using a cutter’s hand hammer and lettering chisels of various widths, following a mental image of the lettering content, style and layout. Early gravestones include examples where the stonecutter did not plan ahead and ran out of space, having then to use an abbreviation or reduced-size letters. More careful workers might trace a design on the stone before cutting, perhaps using a straight edge and lettering block. It soon became clear that much better results were achieved when a draftsman created a full-sized detail drawing of the lettering. Usually, this drawing was shown to the customer who signed it, verifying that he was satisfied and that there were no misspellings or other mistakes. The stone letterer usually owned several dozen ½-inch lettering chisels since there were always some being sharpened. Also, he had perhaps a dozen 1/8-inch to 3/8-inch chisels to cut inside the letters (for example A, B, P, R) and narrow places on the outside. For raised letters, he would have a dozen or so 5/8-inch points to work down the background. For the background, some raised letter carvers preferred using a sequence of roughers: a ½-inch four-point chisel, a 1-inch double-row toothed chisel, a 1-inch single-row toothed chisel, a 1-inch double row plain chisel, a 1-inch single row plain chisel, and a small bush chisel, of which they would own several of each. Initially these would have been hand tools, but later these would all have been adapted as bits for the pneumatic hammer (Figure 46).
Sandblasting was used as early as 1875 by Sheldon and Slason of West Rutland, Vermont, to cut letters on Civil War gravestones. Chilled iron shields or stencils were used to cut both sunk and raised lettering. Sandblasting was introduced to the granite industry in a major way around 1915 and revolutionized letter cutting and shape carving. Stones to be lettered were put on sandblast skids and wheeled into a stencil cutting room on a hydraulic lift truck. The typical steps in sandblast carving are: creation of the design; drafting of a full-size detail drawing; cementing a rubber stencil onto the stone (rubber mallets and rollers were used to insure that the stencil adhered uniformly to the stone); transferring the design from the detail drawing to the stencil; cutting the stencil with a stencil cutting knife; and sandblasting (blowing) with silicon carbide. Some stencil cutters did both stencil cutting and sandblasting. In 1925, lettering systems were introduced that provided templates for letters of different sizes and fonts (Figure 47). Stencil-cutting machines that could cut letters of different sizes and fonts were introduced in 1968. Sandblast letters do not have as sharp and well-defined edges as hand-cut letters and the bottoms are a more rounded U-shape. Although the sandblast edges can be sharpened with a small hand-held grinding wheel, the practiced eye can still distinguish the two.
Shape carving is three-dimensional ornamentation such as flowers, fruit, leaves, vines, and religious symbols. The best of shape carving takes great skill and long training. For hand shape carving, the tools used are very much the same as those for bas-relief and full round carving. For sandblast shape carving, the stone was blown with fine steel shot abrasive in two or more passes, at each pass cementing on some parts of the stencil that had been removed for the initial sandblasting and cutting additional fine lines in the stencils. The final finishing pass was done with silicon carbide. As with lettering, systems were introduced for shape carving that provided templates for the most common designs of flowers, fruit, vines, religious symbols, and such (Figure 48).
When a stone was ready for sandblasting, it was moved on a sandblast skid into an illuminated steel blowing, or sandblasting, room through a large door at one end of the room (Figure 49). Operator access for the sandblast hose and nozzle was via a blasting curtain and viewing was provided by a window above the curtain. A blast generator blew aluminum oxide abrasive at high velocity and pressure (100 psi) through a sandblast nozzle. Nozzle materials have progressed from hardened iron to ceramic to tungsten carbide to Diamonite (a sapphire-like material) to boron carbide, which is the longest lasting material. The abrasive would cut only the stone surface not covered by the stencil. The sandblast curtain allowed access while at the same time preventing the airborne granite and abrasive dust from leaving the blowing room. The used abrasive fell through a floor grating into a pit beneath and was re-circulated by a sandblast abrasive elevator that cleaned, elevated and stored the abrasive for reuse. Some recent sandblast outfits have “automated curtains” in which the nozzle is moved under computer control and can carry out most or all of the sandblasting without operator intervention. The need to add at least the date of death to an already erected monument has led to the design of cemetery sandblast units that include a portable air compressor, portable sandblast generator, and cemetery lettering sandblast curtain (Figure 50).
Sculpting and Modeling
The creation of a stone carving normally involved three steps: the designer’s drawing, a plaster model, and the final execution in stone. The designer, artist, or architect provided the original conception in the form of a drawing or blueprint. A sculptor then gave the conception a three-dimensional representation in the form of a model (Figure 51). Finally, the carver, using the model as a guide executed the ornamentation, bas relief, or full-round statue. Sometimes a maquette, half size or less, was produced and the carver had to scale up in order to carve the full-size stone sculpture. Often a small plaster model was created as an approval model before the full-scale or maquette model was sculpted. For large commissions, each step may have been executed by a different person. For small or medium-size projects, often two or more steps were executed by the same person. Some pre-1940 noted Barre, Vermont, sculptors were Carlo Abatti, Angelo Ambrosini, John Comi, Elia Corti, William Corti, Enrico Mori, Samuel Novelli, Augusto Sanguinetti, Lambruno Scrzanini, and Gino Tosi. The 1899 Robert Burns monument in Barre, Vermont, was sculpted by Massey Rhind and carved by Samuel Novelli, and the pedestal bas-relief was designed by James B. King and carved by Elia Corti. It is one of the world’s outstanding examples of full-round and bas-relief granite carving (Figures 52 and 53).
Referring to the design drawing, the sculptor would create a three-dimensional clay model using a variety of clay sculpting tools. The clay would sit on a sculptor’s turntable illuminated by a portable, adjustable-height lamp. At this point, the customer and/or designer was shown the model (or a photograph of the model) and would often suggest changes to the model before carving (Figure 54). From the clay model, a plaster mold would be produced. Thin pieces of overlapping tin were stuck in two lines into opposite sides of the wet clay model and projected about six inches above the clay. The clay model was then covered with a thin mixture of colored plaster of Paris, making sure the plaster penetrated into every fold and crevice. As soon as this layer had hardened, several additional layers of thicker plaster were added until a thickness of about six inches was achieved. After this had dried and set, about twenty-four hours, the two halves of the plaster mold, separated by the tin pieces, were removed. Any remaining parts of the clay model that still adhered to the mold pieces were removed, usually destroying the clay model in the process. The mold pieces were washed out, dried, and a special grease was applied to the inner surface to prevent sticking. The mold was then reassembled and used to create the final and more durable plaster model. First, a thin plaster was poured into the mold, which was turned in various directions to insure the plaster filled every detail in the mold surface. After this layer had set, several additional layers of thicker plaster were built up to provide strength for the model but leaving a hollow center. Finally, after the plaster had set, the mold was removed, breaking it if necessary. Any colored bits of plaster from the mold still adhering to the white model were carefully removed.
Various materials, liquid latex or liquid vinyl, are now available that can be painted on the clay model to form a mold. About a dozen quick-trying coats of latex are painted onto the model and then a plaster mother mold is poured around the latex-covered clay model. The mother mold is removed and the latex is removed from the clay model and put into the mother mold. Finally, plaster is poured into the latex-coated mother mold to create the plaster model. The vinyl mold-making material is painted on and after baking is stiff enough to use as a mold without the need for a mother mold.
Carving
The carver had to understand and carry out the intentions of the designer and sculptor. However, the surface treatment and expressive details belonged to the carver. The carver’s responsibility was very similar to the musician’s in interpreting the intent of the composer. The process of sculpting in clay and carving in stone is very different. Sculpting is a process of addition (putting on) whereas carving is a process of reduction or revealing (taking away). What a sculptor takes off can be put back on. What a carver takes off can’t be put back. Although this is not entirely true since many carvers have their own specially formulated filling compounds that can be used in certain situations. Carving involves reduction and risk and requires great patience.
Stone workers were classed in three levels of increasing skill: stonecutters, ornamental carvers, and figure carvers. A student, on his way to achieving master carver status, usually passed through these three levels. Each level brought increasing respect and pay. Stonecutters did the rough shaping of stone-into flat or curved surfaces that may be chiseled, hammered, rock faced or polished. The stonecutter may have been aided by a variety of machines such as surfacers and polishers. Carvers almost exclusively used hand-held tools-some powered by compressed air. Carvers who did primarily artistic work were more highly respected than those who did primarily repetitive commercial work. The master carver went beyond technical skill to a true creative and artistic level. In final finishing, the most skilled of the master carvers gave the stone movement, grace, realism, power and life-even tenderness and emotion. He did this through a combination of shadow-chiaroscuro, contrast, texture and color.
The master carver typically owned and used a few hundred hand tools. These included pitching tools, chisels, gouges, files, rasps, wood mallets, steel hammers, drills, pointing machines, calipers, carpenters’ squares, level, plumb bobs, rulers, tape measures, straight edges, scale triangles, scribers, pencils, sandpaper, sandpaper blocks, Carborundum stones, carvers’ turntable, lamps on an adjustable stands, and safety glasses. The carver also used a small pneumatic carving hammer- a ½-inch bit shank and a ¾-inch or 1-inch piston diameter (see Figure 44)-with: a point or roughing chisel for heavy removal and rough usage; a carving chisel for general carving, sculpting, and lettering; a cleaning-up chisel for finishing that scrapes and closes the grain; and a carver’s drill that drills small-sized, round holes for detail carving (Figure 55). Often, the carver had a favorite dozen or so tools which he uses most of the time.
After selecting a granite block, holes were drilled around the statue outline, and the excess was broken off with a hammer and chisel. Rough shaping was commenced with a hammer and chisel. A carver’s apprentice may have done the initial roughing out. Plane surfaces were cut on the three-dimension figure using a pneumatic hammer with a point, a ripper, a four-point tooth chisel, or bush chisel. The pointing machine was used to transfer distances and relative locations from a plaster model to the stone as it was being roughed out, insuring that the sculpture closely followed the model. The pointing machine consisted of a main vertical rod with several horizontal rods connected to the main rod by setscrew-tightened clamps (Figure 56). Small-diameter pointed rods were connected to the vertical and horizontal rods also by setscrew-tightened clamps. The pointing machine was first adjusted so that its points were resting on reference points on the plaster model. The sculptor would have previously embedded reference points (metal pins) in the model for use by the pointing machine. Then the machine was moved to the stone where the points established the same reference locations. The machine was usually moved back and forth a number of times as the roughing out progresses, each time adjusting the number and location of the points. For a large sculpture, two or more machines would have been used. A typical pointing machine was 28 inches high by 20 inches wide but could be custom-ordered in larger and smaller sizes.
Once the stone was roughed out close to the finished surface, the pneumatic carving hammer with a nine-point tooth chisel, double-blade chisel, three-blade chisel, bush chisel, criss-cross chisel, or cup chisel was used to bring the stone almost down to the final surface. The carver would go over the statue from head to toe many times with a fine pneumatic chisel-each time adding more detail to face, hands, feet and clothing. Usually, the final detailing and smoothing was done by hand with finishing chisels and gouges, fine drills, files, rasps, and sandpaper.
Washing and Boxing
The washing and boxing stand was typically constructed of 4- by 4-inch wooden beams. The stone was set on the stand and washed with muriatic acid to clean off steel shot fragments if it still had sawn surfaces exposed. Otherwise, the stone was washed with a weaker cleaning solution. The sandblast stencil was removed, having been left on to this point to protect the polished face from scratching, and the stencil cement was cleaned off. The acid was stored in a five to ten gallon stoppered glass jug that was kept in a tilting acid stand. The acid was decanted into gallon acid jugs by tilting the large jug. The gallon jug had a six- to eight-inch hose in its mouth so the jug wouldn’t break against the stone. First the stone was wet down. Then acid was poured on from the gallon jugs and scrubbed in with an ordinary scrub brush. The washers used rubber gloves and some also wore rubber aprons. For a stained area where abrasive shot had lain for a period, extra acid would be used and additional scrubbing done. Finally, after it had set a short while, the acid was rinsed off with water.
The washing and boxing stand had a small boxing crane to lift the stone onto a crate bottom. The crate bottom had a slot so that the lifting rope could be easily pulled out. The top of the crate was put on, the corners put on and the whole secured with steel straps tightened with boxing tongs. Recently, the increased cost of lumber has lead to a simplification of crate designs requiring less wood (Figure 57). The crated stone was then placed on a transfer car and taken to the finished granite storage area. This was the shipping area from which crated stones were sent to the customer. Crated standard-size monuments were also kept in the storage area to fill rush orders. These were produced during the winter when business was slack.
Transport and Setting
Granite for long-distance shipment was often consolidated into a single railroad flatcar load of both slabs and finished work for multiple customers-often 120,000 pounds on one flatcar. The stones were braced and wedged between hardwood car stakes so they wouldn’t shift during transport. An expert car loader could so perfectly balance a load that he could stand on top of a fully loaded car and make it sway on its springs (Figure 58). The services of a well car might be needed to transport extra large stones. The well car had an open center or well in which a mausoleum roof stone or a large column capital could be carried just a few inches above the rail bed so they would fit under bridges and through tunnels (Figure 59). By the 1950s, trucks were doing most of the granite hauling (Figure 60). In some cases, the truck would take the stone to the local depot for rail shipment.
Author
EAIA member Paul Wood is a retired electrical engineer, who worked his entire career in the computer industry. He is interested in the tools, implements and machinery of the granite industry and of nineteenth- and early-twentieth-century farming in New England.
Copyright Early American Industries Association Dec 2006
Provided by ProQuest Information and Learning Company. All rights Reserved
