Granite Engraving

 


There is a famous Norman Rockwell painting of a man leaning over a block of granite, working at laying out the design. This is where the actual process of engraving granite begins after all the decisions about lettering and design and artwork have been made. In the old days, the layout was drawn directly on to the stone and cutting was done largely by hand with hammer and chisel. Nowadays, most of the cutting is done by sandblasting through a thick rubber stencil and optionally hand-finishing or "tooling" using special pneumatic chisels. 

Sandblasting involves spraying a mixture of air and hard silica sand or aluminium oxide grit through a nozzle at about 100 p.s.i. (pounds per square inch) pressure.  Obviously, this is not a very precise procedure --a bit like trying to letter a sign by spray-painting, but (in both cases) there is a solution; using a stencil.  In the "old days" of sandblasting lettering, the stencil was made of rubber melted in a hot-pot and "painted" onto the granite.   After it cooled, the lettering was drawn on it and then cut out with a sharp knife, not unlike cutting cookie shapes out of rolled dough.   During the sandblasting procedure the sand simply bounces off the rubber, but slowly chips or etches away the granite left exposed by the cut-out areas of the stencil.

Modern sandblast stencil consists of roles of sheet rubber, about one eighth of an inch thick, which are cut and glued to the granite with latex rubber "filler". The lettering and artwork can be pre-cut and removed on these sheets (a special plastic backing holds the centres of letters in position). Cutting the stencil is done by hand, press, or computer controlled machinery. [The "press" works in a manner similar to using "cookie cutters" on rolled dough].

There are many techniques and variations in the way stencil (and different stencil materials) can be used for special effect.  For example, stencils can be removed/reapplied in stages for a controlled 'frosting' look, or special wire stencils for knurled or 'cut glass' designs. It is also often desirable to do special shape-carving with hand-held precision sandblast nozzles and pneumatic Carver's tools to add shape and texture design work such as floral patterns, 'praying hands' and other ornamentations. Shape-carving is standard on Lons memorials at no additional charge.

Stencil cutting, by its nature, is limited to bold shapes and lines generally at least 1/8 of an inch wide. Although there are several techniques for adding some basic shading and texture to enhance this type of engraving, fine detailing is not possible. When photo-realistic images (such as portraits) are required, they can be reproduced from photographs or re-created as original works by an artist directly engraving  the polished granite. In order to show greater detail, less material is removed in a process more properly called "etching".  The artist uses a variety of tools to accomplish this, including light sandblasting ("dusting"), high speed die grinding,  carbide or diamond detailing and texturing tools, and occasionally, highlighting acids, dyes, and solvents.
  There are also specialized machine techniques for reproducing  photographs directly onto granite and other durable media such as bronze, glass, and even in colour on ceramic plates which can be added to a monument.  


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