March 5, 2010

Sculptural Stone Qualities: Color, Texture, Workability

Color
Selecting stone for sculpture brings several considerations to the process.  Color perhaps represents the most obvious outwardly telling attribute of a stone.  Different colors or combination of colors can enhance or diminish the perception of form in a sculpture.  The way light plays on the stone for shadow and highlight perception establishes the basis of how we perceive shape or form in a stone sculpture.  White stone shows the nuances of shadow far more obviously than a black stone simply because shadow shows clearly on white while shadow virtually vanishes on a black surface.

Similarly, complexly textured or striated stone conceals shadow and highlight in a complexity of surface lightness and darkness.  Darkly colored or complexly colored stone offer inherent desirable qualities in the color attributes, but challenge clear portrayal of form.  This might suggest using dark or complexly colored stone to portray bold or simple forms, rather than attempting to render surface details of fine texture or intricate detail.

Nuanced form sculpted in white Yule Marble

Bold  form sculpted in basalt

Nuanced form sculpted in black basalt

With that said, there are creative opportunities to exploit dark color or complex coloration as elements of detail.  Combining such elements as stone surface lines with sculptural inclusions, layers of detail not possible through sculptural working alone become possible.	Strong contrast variation of Zebra  Marble coloration
Close-up of Breccia Marble complex coloration

Texture Each type of stone has an inherent natural surface which can be finished only as far as the material will allow.  Examples range from the gritty surface of sandstone which can only attain a gritty feel while more finely grained stone such as Carrara Marble may be worked to a very high smooth polish.  Each type of stone offers textural qualities which may yield specific, predictable results.  Sometimes the rough, grittiness of sandstone can be employed to capitalize on such a rustic feel.

Complex striations of Picasso Marble

Granular surface of course sandstone

Workability - Hardness, Strength, Integrity
One aspect of stone texture relates to how the stone can be sculpted and finished.  Such qualities relate to workability of particular stone types.  Here stone hardness comes into play.  Soft stone can generally be worked more quickly than hard material and also requires different tools to accomplish the work.  Soapstone and alabaster can be worked with tools commonly used in working wood.  Many types of soapstone and alabaster will also polish to a high finish, while others not.  By contrast, granite must be worked with much more durable tools better matched to the markedly harder character of granite.  Once again, some types of granite will polish well, while others not.

Nuanced form sculpted in white Yule Marble with prominent shadow dramatizing the form

Bold  form sculpted in Picasso Marble with complex striations and subtle shadows

Close-up of Picasso Marble complex coloration/striations

In between the commonly used soapstone and granite sculptural stone types are sedimentary stones like travertine, and limestone.  Then there are the metamorphosed stone such as marble.  Within each stone type, specific stone origins can yield rock either harder or softer than average for the stone category.  For instance, among marble, Picasso Marble is significantly harder than Yule Marble.  Both can yield finished pieces with fine surface character and even take a high polish when desired.  Be contrast, some limestone while offering wonderful sculpting qualities, can only be worked to a flat finished because the stone grains are too course to polish.  Then there are gritty stone types like sandstone which generally lack a fine enough texture to polish at all.  Of course polish is a relative term.  While high gloss usually defines polish, some stone will work to a very smooth, satiny finish which can also be considered a polish, tough not yielding the sheen of high gloss.  Sometimes a high gloss can distract from the sculptural form when highlights overwhelm the nuance of shadow on the piece.

Beyond hardness and surface characteristics, stone integrity carries particular challenges to workability.  Some stone contains zones of varying hardness which make for uneven workability.
Then there are rocks that conceal fractures that weaken and break as the piece is worked.  Fractured stone is very common in material collected from the surface of the ground where natural forces act to weather and deteriorate the rock exposed to the elements of weather.  Using quarried stone usually avoids problems of weathered stone.  However, many stone sources only offer surface collected material because quarrying and mining add an expensive level beyond the capacity of many suppliers.	Sculpture in Zebra Marble which has strongly contrasting coloration	Dramatic form sculpted in white Yule Marble with subtle shadows and highlights dramatizing the form

Stone integrity also involves inherent strength.  Strength offers several qualities of workability that can give a finished sculpture a finer form then a less strong stone offers.  This shows up in how thin a particular stone of a certain mass can be worked without breaking.  Some stone offers a very uniform makeup throughout.  This makes that stone more dependably workable to a thin profile that can support more mass than a stone with internal inconsistencies that may fail when worked too thin.  Such integrity and strength can only be fully discovered as the sculpture emerges.

Example of unpredictable, hidden fracturing in Picasso Marble found only after working the piece

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