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Sandblasting is a stone cutting process that uses compressed air to spray granular abrasive at high velocity onto the surface of the stone. The sandblasting generator forces the abrasive through a sandblasting nozzle at high pressure (up to 100 psi). The abrasive cuts only the surface of the stone that is not covered by the stencil. The first tests of sandblasting took place in Barre around 1915, but it took many years to perfect the sandblasting process. When sandblasting technology was widely adopted by the granite industry, it revolutionized letter cutting and figurative engraving. By 1937, Jones Brothers had an alcove that housed four Rumelin blast rooms and an additional stencil cutting room (the “blast studio”) for 10 stencil cutting machines. On the ground floor of the Jones Brothers office building was a drafting room with six or seven draftsmen. In the early days of stone lettering, masons simply carved freehand, using hand hammers and chisels of varying widths, following a mental image of the content, style, and placement of the letters. There are examples of early tombstones where the masons did not plan ahead, had no space, and could only use initials or reduced-size letters. A more careful worker might have traced the design on the stone before cutting, perhaps using a ruler and lettering block. Stone engravers often have dozens of 1/2-inch chisels for engraving because there are always some that need sharpening. In addition, he has about a dozen chisels ranging from 1/8 to 3/8 inches to cut the tight spaces inside the letters (like A, B, P, R) and outside. For the raised letters, he needed a dozen chisels that were 5/8 inches in diameter to cut the background. For the background, some relief letter engravers prefer to use a series of coarse chisels: a 1/2-inch four-point chisel, a 1-inch two-prong chisel, a 1-inch single-prong chisel, and so on, of each type, including a 1-inch two-row flat chisel, a 1-inch single-row flat chisel, and a small bushing chisel. Two-dimensional sandblasting (“flat engraving”) of names, dates, and graphic and symbolic outlines is done with silicon carbide, whereas aluminum oxide abrasives are used today. The edges of sandblasted letters are not as sharp and crisp as hand-carved letters, and have a more rounded “U” shape at the bottom. Although sandblasted edges can be smoothed with a small hand grinding wheel, a trained eye can still tell the difference. Figural carving – carving three-dimensional designs such as flowers, fruit, leaves, vines, human hands and religious symbols – is done with steel shot. Figural engraving adds depth and detail, making the engraving more realistic. Carving the best shapes requires great skill and training – for the best results, “you can almost smell the granite roses, it even fools the bees.” Steel shot is also used to give the monument an overall “seasoned” or “powdered” appearance. ” surface. Steps The sandblasting process in the early 1970′s consisted of the following steps. First, an artist or draftsman creates an original design and documents it with a sketch. The draftsman then creates a full-scale detailed drawing based on the sketch and presents it to the client for approval. The shaper (or rubber cutter) then adheres a rubber sheet mold to the stone, using a rubber mallet to ensure the mold fits evenly. He places the full-size pieces face down on the stencil, rubbing the back of the stencil to transfer the design details onto the stencil. He then uses a very sharp stencil knife to cut the stencil along the transferred lines and remove the cut letters, numbers and patterns from the stencil. The sandblaster (or blower) now loads the stone onto a sandblasting sled, uses a hydraulic lift to push it through a gate at one end of a well-lit steel blast chamber and stands it upright so that The formwork faced the blast chamber windows. The sandblasters then cut letters and shapes into the stone using templates. Access to the blast hose and nozzles was through a blast curtain, and viewing was through a window above the curtain. The blast curtain prevented granite and abrasive dust from escaping from the blast chamber. After the first stage of sandblasting, the form cutter could add or remove additional rubber sheets to achieve special effects. Some form cutters were also sandblasted. Patents Joseph Ladrie of Barre, owner of Hebert & Ladrie, received a patent for a sand curtain (July 3, 1934, Patent No. 1,964,920). This design reduced the size and number of glass windows, allowing them to be moved on rails to the location where the stone was being sandblasted. Side curtains kept the blast chamber closed. Some modern sandblasting equipment has “automatic curtains” in which the nozzle moves under computer control and can do most or all of the blasting without an operator. In the early 2000s, Sherman Cochran of Barre developed and sold two computer-controlled sandblasting devices: the Stencil Cutter (a computer-controlled stencil cutter) and the Sandman (a computer-controlled sandblasting curtain). The products are based on existing products from companies such as Gerber, Allen Datagraph, and Vytek, and are created using the artistic design expertise of Gino Tosi, Jr., son of famed Barre sculptor Gino Tosi. The abrasive is cut into exposed stone (not covered by a template) with silicon carbide or aluminum oxide by moving the nozzle back and forth a few inches above the template. The spent abrasive falls through a floor grate into a pit below the blast chamber and is recirculated through a blast elevator that cleans, lifts, and stores the abrasive for reuse. Next, the formed three-dimensional profile is cut with fine steel shot. Close off some of the engraved areas of the mold by replacing some of the removed portions of the stencil to protect the engraved areas of the previous mold from further sandblasting. Cut the fine wires on some of the replaced areas of the template and remove the rubber from these wires. Clean the stone two or more times with fine steel shot. During each blast, other portions of the formwork removed after the initial blast were glued in place and additional fine lines were cut into the formwork. Use silicon carbide for the final sandblasting. Finally, remove all portions of the stencil and clean off the adhesive. Three Vermont residents have patented a procedure involving the use of a series of rubber templates. Robert Perry of Barre, a draftsman for Rock of Ages, patented a method for creating decorative patterns in stone (1937, Patent 2,071,086). The patent describes a systematic procedure for creating contour decorative patterns by sandblasting using a continuous template. Robert Knox of Berlin, a draftsman for Jones Brothers, received a patent for sandblasting (Patent No. 2,156,696, May 2, 1939). The patent describes a method of sandblasting a pattern of different decorative items on a single area. As in traditional sandblasting, a rubber template is used first, followed by a second round of sandblasting using a second template that is bonded to the initially sandblasted surface. Alfeo Brucetti of the Rose-Crest Sandblast Co., Barre, patented a method of carving stone (Patent #2,671,978, March 16, 1954). Key innovations include the use of replaceable template sections to prevent sandblasting from damaging nearby finished areas, sandblasting undercuts to cut thin, realistic petals, and the use of steel shot (for the white petal surfaces) and emery grit (for the blue background) to create contrast. Rather than spending a fortune on a sandblasting booth, sandblasters could use a protective helmet with a window that trapped uncontaminated air from a compressor. The April 1924 issue of Granite Cutter Magazine featured a photograph of a blast booth equipped with a wall-mounted fan and blasters wearing air-supplied helmets. The headline read, “This Device Removes All Dust from a Sandblasting Room. Developed by N. D. Phelps Company, Inc., Barre, Vermont.” In the 1920s, N. D. Phelps Co., a hardware store on Main Street, installed a wall-mounted exhaust fan. It’s a useful measure, but not entirely effective, since the sandblaster still has to wear protective gear.