To polish alabaster all that remains after sanding with 600, 800, 1000, or 1200 grit is to apply paste wax and buff the surface with a clean rag or lambs-wool buffing pad.
For darker soapstones wax will leave a shiny surface, but it will not be as dark and rich as the stone appears when wet. To achieve the rich natural color depth of the stone a common practice is to apply linseed oil (preferably the boiled variety) to the surface, allow it to stand until it is absorbed as much as possible into the relatively non-porous surface. After perhaps fifteen or twenty minutes wipe away all the excess oil with a clean, lint-free rag. Set the piece aside in a dust-free environment for ten or twelve hours (or overnight) to allow the remaining oil to dry. The next day the linseed oil process is repeated, and again wiped down and allowed to dry. The first application will deepen the surface color of the stone significantly, but the second application will achieve almost all of the depth possible. Following the oil a light application of wax can be applied and buffed to a soft sheen. This method is NOT recommended for light colored stones as the linseed oil will take on a dark yellowish cast with age.
The above methods will work for other dark stones or marbles as well, but marble can also be taken a step further and polished with tin oxide before waxing.
Again, the surface must first be sanded with 600, 800, 1000, or 1200 grit sandpaper diamond abrasives to remove all visible scratches to the naked eye. Tin oxide, which is a very fine abrasive in the form of a white powder, is mixed with a little bit of water into a paste or slurry. This slurry is rubbed over the surface with felt or tightly wadded cotton rubbing pads. After the entire surface has been completely rubbed with the tin oxide slurry - rub it again! Wash the sculpture with water and rinse away all of the tin oxide. Let the piece dry in the sun and check for any dull-looking areas that missed getting polished. If there are any, repeat the tin oxide process. If the surface looks uniform, it is ready for the final step in finishing.
For the ultimate polish on marble the tin oxide slurry can have a small amount of oxalic acid crystals (commonly sold as wood bleach) dissolved in it. This will increase the gloss of the polish by partially dissolving and re-depositing the calcium carbonate on the surface, filling in the cracks and pores between the crystals of the marble. Note: oxalic acid is toxic in large amounts and will be absorbed through the skin — so rubber gloves should be worn.
SEALING THE SURFACE OF THE STONE
One of the main reasons wax is used is that it helps to seal the porous surface of the marble against stains. This is most important for the lighter varieties of marble, because they stain rather easily. Even areas of the stone that are not polished should be waxed. To seal effectively, the wax needs to penetrate into the pores of the stone as much as possible.
There are special very-specific types of waxes that are formulated specifically for marble and alabaster. These polishing fluids (solvent-base Akemi Polishing Fluid #2012 is my personal choice, but there are water-base and silicone-base types as well made by Akemi and other brands) are designed to enhance the optical properties of the stone surface, giving depth to the colors and veining of the stone. These are considerably more expensive than common paste waxes.
If employing common paste waxes - especially on alabaster or light-colored marbles - make sure to use the clear or neutral types (Renaissance Wax, Trewax Clear Paste Wax, Kiwi Neutral Shoe Polish will all work) so the color of the stone is not adversely affected, and it is important to use the barest minimum of the wax on the surface to achieve a seal. To prevent streaking the wax needs to be buffed immediately after the surface is completely covered and has penetrated into the pores of the stone. The best way to insure penetration of the wax is to apply the wax while the sculpture is warm - pre-heating the stone in an hour of warm sun will serve nicely. Apply the wax sparingly, and do not let the wax dry on the stone before buffing it with a clean cloth. Too much wax will promote streaks and is sticky and/or gummy to the touch, and viewers like to touch stone sculpture! For applying wax to textured areas, first apply and then remove the excess wax with a soft, clean toothbrush before using the clean cloth to buff.
. . . OR NOT TO POLISH?
Because the material of stone itself can be so inherently beautiful in terms of depth and richness of color, veining, and patterns, stone is often polished to best reveal those characteristics. However, other aspects of the nature of the material are also important in stone carving. If one considers that light, shadow, and color are the primary defining elements for the visual senses, then texture must be considered the primary defining element in the tactile senses.
The feel of a high polish is certainly sensual, but like so many other sensual things in life it is often the contrasts between colors, between flavors, between types of sound that produce the harmonies that give the depth and richness to images for the eye, gastronomy for the palate, and music for the ears. By itself a highly polished surface can seem sterile, cold, and uninviting. But by contrasting that very revealing high-polish on stone with a variety of textures the carver/sculptor can express much more about the creative process and, through this, about the feelings and characteristics of the subject portrayed.
In representational work this might mean a preponderance of smooth polished surfaces in portraying a beautiful body, or a carefully chiseled surface to reveal the powerful strength of an athlete or warrior, or perhaps a sandblasted and worn surface to portray a wise and experienced elder statesman — the textures enhancing and adding to the details of the form. In more stylized or abstract works the applied surface textures take on a more important role because there is not a direct representation of a recognizable subject that is being modified, but instead the texture is one of the primary ways for the viewer to understand the forms themselves.
TYPES OF TEXTURE AND FINISH
There are many ways to employ and produce texture in sculpture, the following list categorizes the primary methods:
Natural or As-Found — where the surfaces are left or appear to be left as they were when the sculptor acquired the material. This would include naturally-occurring patinas of age or weathering, but also evidences of more distinct events that may have been done to the piece of material — i.e., quarry markings, splitting, damage, paint splatters, etc. Sometimes other processes can be used to mimic these types of occurrences on the surface of the form in altering shape, repairing damage, etc.
Polished — Though polishing is actually an abrasive process, because it is the ultimate state wherein the surface has been tooled and abraded by sequentially finer stages to remove all traces of any tooling, it thus reveals the inherent colors, patterns, and minute textural details of the material matrix. The degree of polish can and does vary depending on the tools and methods available, but the defining sense as used here is that there are no surface scratches are visible to the naked eye. Means of producing different types of polished textures would include hand and power sanding with abrasive papers or diamond pads, stick or paste buffing compounds applied with sewn cotton, felt, leather, or rubber buffs, and chemical alteration of the surface with acids.
Abraded — one of the stages in obtaining a polished surface where the surfaces are scratched by an abrasive tool or material. This differs from a tooled surface in that although the size and degree of the scratches left on the surface might vary, there are no specific further indications of the type of tool that might have been used to produce the results. Means of producing different types of abraded texture would include — but not be limited to — sanding, grinding, sandblasting, filing, rasping, etc.
Tooled — though it may be one of the stages prior to abrasives in obtaining a polished surface, it is also where the surfaces have been deliberately marked by a specific application of a particular type of tool. Though the tool used may or may not be an abrasive tool, by definition a tooled surface has distinctly identifiable marks. Means of producing different types of tooled texture would include — but not be limited to — bushhammering, chiseling, grinding, brushing, sawing, drilling, splitting, etc.
Color Alteration — where the surface has had some manner of alteration from the naturally-occurring color of the material as worked. Though the appearance of color in a tooled surface is different from an abraded or a polished surface in the same material, this alteration is inevitable whether it is used intentionally or not. The application of a ‘transparent’ sealer such as wax or oil will also inevitably change the appearance of the color just as much as the use of pigment, though perhaps not always to the same degree. All of these potential color-altering methods should be considered as types of visual textural finishes, whether as a by-product of another process or specifically done with the intent of changing the appearance.
Note that texture produced by any method — but especially with tooling — is achieved by working the surface through a series of separate events. A single occurrence results not in texture, but rather evidence of a discrete event — thus perceived in a completely different manner by the viewer. Texture occurs only when the individual events are subsumed into an overall series of marks that create a repeated pattern.
RULES OF THUMB
Some general rules-of-thumb for the choice or use of texture and/or the application of texture:
The number of textures on a particular piece should be limited — too many textures will tend to confuse the viewer as to what is happening within the composition of whole design
It is easier to access and work on projecting portions of the carving, and conversely more difficult to access and work on recessed areas of the carving: therefore; the application of necessarily highly-controlled or detailed textures should be limited to the projecting portions if possible, while simple and easily-worked textures should be reserved for the recessed areas if possible. That point made, sometimes the design demands it the other way around, and when the design demands it the extra work is probably worthwhile.
Tactile textural contrast is more dramatic when accompanied by tonal contrast — so when desiring the greatest potential visual impact out of applied textures it is best to emphasize both the tone, color and the tactile nature of the adjacent textured surfaces by contrasting all the differences between them. [using contrast is a way of being precise, clear, and easy to understand in your visual statements]
When the form of a work is composed of highly-detailed representational elements the visual qualities of the material need to be more regular or uniform so the viewer can ‘make-sense’ of the textural details without being distracted by the inherent visual textures of the material. [this is why uniform white marble was so highly valued by the carvers of highly-detailed naturalistic representations in past centuries]
When working with a highly-figured or veined material the design of the form should be kept as simple as possible stylistically so as to allow less clashing between the visual nature of the material and the appearance of the form — this might include deliberately keeping the degree of polish to a low gloss in areas where the form is more complicated, or changing the scale of the work so the inherent visual textures in the material become less intrusive to the viewer’s perception of the overall form. [one might say this is an instance of using inherent visual texture to help design potential form]
During initial viewing of a work the viewer’s eyes are unconsciously but quite naturally drawn to areas of the form that can be considered to be ‘highly-refined’ rather than to what seems to be ‘background’ — this would include highly-polished areas vs. rough areas, areas with a great deal of minute detail vs. areas of smooth or uniformly textured/featureless surface, or if the subject is representational/figurative to areas that denote recognition and expression (such as faces, eyes, mouth, hands) or areas that are potent with sexuality vs. the relatively innocuous middle of a limb, section of torso, or the hair on the head. This means the way the sculptor handles the textures in those areas will control how the viewer reacts to the subject — specifically; whether the viewer reacts with appreciation or with disappointment. These focal points are where the greatest scrutiny will occur, so they are not places to cut corners on craftsmanship, but rather where textural differences should be crisp, distinct, and carefully wrought. [human nature is such that we all are drawn to shiny, unique, precious, and forbidden things — use that fact to make the viewer understand what you want them to]
If applying color to a natural stone care should be taken so that the relationship between the applied color and the natural colors don't clash unnecessarily — a little bit goes a long way. The concept of 'truth to material' is a potent one, and while some might politely say applying color to natural stone is "gilding the lily," it more probably means they consider it more as "painted-up like a whore." [not something you want your viewers to think about, right?]