CHOOSE THE STONE

SURFACES

CHOOSE THE STONE

SURFACES

The surface finish of a stone material characterizes its expressive value: the planarity varies, the colour and the texture are enhanced or attenuated also according to the processing carried out. The same physical properties can change as a result of the processing and chemical treatments used, through these it is possible to respond to specific requirements such as obtaining a certain degree of slipperiness, improving resistance to atmospheric agents, facilitating surface cleaning, enhancing the colours, etc.

Intended use, expected aesthetic result and actual workability of the material, are the three factors that guide the choice towards this or that surface finish. It is necessary to keep in mind that marbles, granites, travertine and natural stones are different from each other and therefore some finishes can be made on certain materials and not on others, with an aesthetic result that will be different from stone to stone even with respect to the same processing.

The main processing and treatments that can be performed on the surface of stone materials are described below:

SURFACES OBTAINED BY ROCK DISJUNCTION

These are rough surfaces obtained by rock splitting, natural or artificially induced.

NATURAL CLEFT SURFACE

It is the surface directly outcropping from the extraction basin of stones that are already split in slabs by nature and that therefore can be extracted already with the surface with which they will be installed. The flatness of the surface shows a certain irregularity depending on the intrinsic characteristics of the nature of the stone and the quality of the quarrying basin. For some stones and especially for products and sizes of greater value, it is possible to have a "first choice" sorted by the most common "commercial choice". The roughness of the surface, the differences in thickness present in the product and the natural variability of the colours are characteristics that feature the stones available with natural cleft surface, usually particularly suitable for the construction of external paving.
Stone materials commonly used with natural cleft surface:
PORPHYRY/ QUARZARENITE / CALCARENITE / some QUARZITES
Natural cleft surface
Cleft surface

CLEFT SURFACE

The final appearance of the stone material is given by the splitting operation: what is exposed is therefore a natural latent surface, that is, not expressible except through the artificially induced material breaking and separation. In nature there are different levels of subdivision of the stone materials: there are stones that are sufficiently compact to produce blocks that can be easily broken up to a millimetre thickness (e.g. the Ligurian slate and the Cardoso stone) and flakable materials according to preferential divisibility plans almost parallel to the installation surface that give rise to products of varying thickness imposed by the surfaces installation (e.g. Luserna Stone, Beola Stone and gneiss in general). Generally the surfaces achieved are distinguished by a discrete flatness that depends on the nature of the stone and the skill of the stonemason in recognizing the right points for inducing separation. The stones with a cleft surface are particularly suitable for the construction of external paving and are characterized by their own natural variability of colours.
Stone materials commonly used with cleft surface:
SLATE / BEOLA STONE / SERIZZO STONE / SEPENTINITE / LUSERNA STONE / CARDOSO STONE / some QUARZITES

SAWN SURFACE

It is the semi-processed surface resulting from the action of frames, block cutters or diamond wire that split extremely compact materials extracted in blocks. The surface of the slabs obtained is the result of a simple mechanical disjunction and therefore it is often possible to show the signs of the tool trace as well as the differences in level, imperfections and defects typical of a surface that has not received subsequent finishing operations. A good flatness and an almost constant thickness feature the final aspect of the material that will be more uniform and damped, useful for camouflaging any aesthetic imperfections naturally present in the stone that would be highlighted by finishes such as polishing or honing. On the contrary many stones with this processing lose a certain appeal, especially if they are rich in shades of colour that will be clearly attenuated. Usually the surface produced constitutes an excellent starting point for subsequent finishing operations by impact, thermal action or smoothing.
Almost ALL stone materials extracted in blocks can be processed by sawing,
but those that are most commonly used directly with this surface finish are:
SANDSTONE/ BASALT / TRAVERTINE
Sawn surface

SURFACES OBTAINED THROUGH IMPACT PROCESSING

These are surface finishes produced by processing historically carried out by hand using percussion tools such as chisels, bush hammers, hammers, scrapers, tooth chisel, now reproduced using modern machines.
Chiselled surface

CHISELLED SURFACE

It is a historical processing performed manually on the surface of the material due to the impact of pointed tools. The trimming (also called chiselling) can be performed on the natural cleft surface or cleft surface, in order to remove the most marked roughness from the surface intended to remain in sight, or on the sawn surface in order to produce, through engraving marks, particular aesthetic effects or shapes such as straight, concentric, oblique or designed lines. Trimming gives a sculpted appearance, regulated by a precise geometry, from which a taste of craftsmanship transpires particularly suitable for classic uses in historical and valuable contexts.
Stone materials commonly processed by trimming - chiselling:
SANDSTONE / CARSO STONE / BASALT / GRANITE

GROOVED SURFACE

It is a surface finish that can be executed both on rough surfaces and on sawn surfaces of particularly soft stones. Historically it was made by hand with tip and mallet in order to engrave grooves in parallel lines more or less wide (8-15 mm) and more or less deep (2-5 mm) spaced with a fixed distance from one to several centimetres. Today it can be reproduced, with a more regular appearance, by diamond disks or by dragging a heavy cylinder with raised grooves and wedges, its rotation generates engravings with parallel lines on the surface of the material (also called roll forming). The final appearance will be a light and elegant texture, composed of dense parallel lines, also functional for improving the slip resistance.
Stone materials commonly processed by grooving - roll forming:
LESSINA STONE / SANDSTONE / CARSO STONE / MARBLES and soft CALCAREOUS STONES
Grooved surface
Bush hammered surface

BUSH HAMMERED SURFACE

Historically obtained manually by percussion with the bush hammer: a hammer with pyramidal head more or less thick with which a quantity of material is removed, more or less uniformly and more or less in depth, hence the name: coarse or fine grain bush hammering. Today, through the use of pneumatic percussion machines, surfaces with reduced slippage are obtained with a noticeable attenuation of chromatic variations in favour of a minimal and clean aesthetic. Bush hammering presents a workability problem along the edges as strong stresses can cause breakages, for this reason most of the bush hammered products have a characteristic "edge" of at least 1 cm which remains smooth and perimeters the bush hammering. Adopted both for paving elements and sculptures or processed items in general, it gives the surface a particular homogeneous and tactile appearance that involves the material texture.
Stone materials commonly processed by bush hammering:
GRANITE / BASALT / SERPENTINITE / LESSINIA STONE / CARSO STONE / PIASENTINA STONE / compact and solid MARBLE and CALCAREOUS STONE

SANDED SURFACE

Sandblasting is achieved by projecting an abrasive mixture of air or water and fine silica sand (or corundum or carborundum) at high speed and pressure or metallic grit (the alternative term: shotblasting). This is a rather aggressive process that increases porosity and makes the material more susceptible to the aggression of atmospheric agents; to mitigate this subsequent finishing by brushing can be followed. For marble and soft or open pore materials (e.g. Travertine) it is possible to work with very fine grits and attenuated pressures (also called: micro-sandblasting) in order not to further accentuate the surfaces discontinuity. Very common for cleaning and maintenance treatments of blackened or graffiti smeared surfaces, sandblasting is also widely used in architectural restoration with the aim of restoring ancient stone or brick surfaces to new beauty. The sanded top appears uniformly rough and grainy but also pleasant to the touch when there are no cavitations or excessive roughness; it gives the material a classic, elegant and delicate look at the same time.
Stone materials that can commonly be processed by sandblasting - micro sandblasting or shot blasting:
SANDSTONE / CARSO STONE / BASALT / BEOLA / SERIZZO STONE / QUARZARENITE / SLATE / SERPENTINITE / MARBLE and CALCAREOUS STONE
Sanded surface
Hydroprocessed surface

HYDROPROCESSED SURFACE

Recent finish that exploits the abrasive potential of water projected with a hypersonic jet, thanks to which it is possible to engrave (but also cut) or drill) the surface of almost any stone material. The hydro-jet (or waterjet) can produce the typical orange-peel effect on some stones as well as a tactile and more or less rough three-dimensional surface that enhances the intrinsic colour of the material. This finish is a valid alternative to flaming for all marbles and soft stones that are not suitable for this processing, in granites it gives roughness without altering the chromatic brilliance of the crystals as instead it happens during the flame treatment.
Stone materials commonly processed by water jet:
SANDSTONE / MARBLE and CALCAREOUS STONE / GRANITE / SERPENTINITE / QUARZITE / SLATE

TEXTURE ENGRAVED SURFACE

Recent machinery equipped with numerical control centers - CCN are able to guarantee extreme precision and computerized management of the abrasive jet (both of traditional type used for sandblasting that of hydro-jet) and allow the engraving of a varied range of patterns on the surface of almost any stone material. Jute, bark, leather, scales, snakeskin and many other textures made with CAD language can be transferred to the material processing by incision using low and three-dimensional high relieves. For even more elaborated and precise texture, able to give shape to almost any fantasy, it is possible to operate through Laser technology also reproducing words or graphics at multiple depth levels.
Stone materials commonly processed by engraving with CCN:
ALL
Texture engraved surface

SURFACES OBTAINED BY THERMAL ACTION

These are surface finishes produced with flame processing.
Flamed surface

FLAMED SURFACE

Flaming is a thermal process that uses oxygen and gas (propane or equivalent) in combustion. Flaming acts by hitting the surface of the stone at high temperature (2.500-3.000°C) causing a thermal shock as a consequence of the subsequent, sudden cooling by immersion in water. This triggers dilation and splitting phenomenon of the quartz and silicon present on the stone surface so that a thin film of material will be removed. Similar to impact processing, even flaming does not act on the colour but on the material texture, making its mining structure and colour emerge. As the processed surfaces will appear vitrified, the resistance to aggression from atmospheric agents and wear erosion will be improved. Flaming is particularly indicated for outdoor applications but it must be used with knowledge only on materials that are able to absorb the strong temperature changes without being damaged, in this sense the maximum yield can be obtained with porphyry, quartzite and hard stones while marble and calcareous stone, except for very rare exceptions, cannot be flamed. Considering that flaming removes material for about 3 mm of depth, if thickness constitutes a precise constraint, it will be necessary to use slightly thicker material before processing.
Stone materials commonly processed by flaming:
PORPHYRY / LUSERNA STONE / PIASENTINA STONE / GRANITE / SERPENTINITE / QUARZITE / QUARZARENITE

SURFACES OBTAINED THROUGH SHAVING PROCESSING

These are surface finishes obtained by levelling with abrasive tools such as grinding wheels, plates, rollers, etc.

BRUSHED SURFACE

Stone materials commonly processed by brushing - coating:
ALL
Brushed surface
Honed surface

HONED SURFACE

Honing makes a surface, usually a sawn surface, perfectly smooth and flat. Depending on the abrasive grinding wheel used, various honing degrees can be obtained:
  • coarse honing is obtained using 60 grit abrasive discs
  • medium or standard honing is obtained using 120 grit abrasive disc
  • fine honing is obtained using 220 grit abrasive discs
  • half-polished or satin finishes are obtained using 400 grit abrasive discs
The final shade will be vivid with increasing fineness of the abrasive grain, while the surface will acquire an opaque and non-reflective appearance. It can be used for interiors or for external covering settings where the climatic conditions would damage the polishing or even in order to give a more sober aspect, in some respects, than polishing.
Almost ALL stone materials can be honed, but those that are commonly used with this surface finish are:
MARBLE AND CALCAREOUS STONE / LESSINIA STONE / GRANITE / PORPHYRY / QUARZITE / QUARZARENITE / BEOLA / SERIZZO STONE / SEPENTINITE / TRAVERTINE

POLISHED SURFACE

Polishing brings a surface, usually a sawn surface, to be reflective as well as perfectly smooth and flat. Polished surfaces enhance the aesthetic qualities of the material to the maximum level, such as colour and texture; on the other hand, they are particularly delicate and sensitive to the action of atmospheric agents, chemical corrosion, and significantly increase slipperiness, especially when wet. Also for these reasons they are suitable only for indoor applications.
Only SOME stone materials are polishable by nature and those commonly used with this surface finish are:
MARBLE AND CALCAREOUS STONES / GRANITE / PORPHYRY / QUARZITE / QUARZARENITE / BEOLA / SERIZZO STONE / SEPENTINITE / TRAVERTINE
Polished surface
Semi-honed or semi-polished surface

SEMI-HONED OR SEMI-POLISHED SURFACE

This is not an incomplete honing or polishing, but a finish that is applied to materials with a rough surface (a natural cleft surface or cleft surface) by honing or polishing. As a result of the irregularities present on the surface, the finish will only act on the parts in greater relief, leaving the most hollow areas unaltered. The end result is an elaborated surface that alternates smooth (opaque or reflective) areas with raw and rough areas, with a particular, sophisticated and predominant aesthetic effect.
Only SOME stone materials available with a natural cleft or cleft surface can also be honed or polished, including:
PORPHYRY / QUARZITE / BEOLA

SURFACES OBTAINED BY CHEMICAL ACTION

These are surface finishes obtained by applying specific chemical products.

ETCHED SURFACE

The surface is subjected to washing treatments with specific chemical products usually acid-based in order to respond to specific needs such as exaltation, attenuation or restoration of tones and colours, increased resistance to atmospheric agents such as salt, smog, acid rain, protection from wear or from surface degradation factors or even to favour consolidation following disintegration of the material due to the action of aggressive external agents.
Stone materials commonly processed by washing with chemicals:
Only those sufficiently RESISTANT TO ACIDS
Etched surface

SURFACES OBTAINED BY A SEQUENCE OF PROCESSING AND TREATMENTS

These are floor finishes obtained from several processes and treatments carried out in succession. There are multiple possibilities of combining the various processes, for example brushing is often combined with flaming or with a large part of impact processing.
Below emphasis is on a process that allows the creation of particular surfaces:

ANTIQUED SURFACE

The surface is given an antique look, intentionally worn and aged by time. The stone products are first tumbled or inserted into tumblers where abrasive aqueous mixtures consume the pieces by rolling and impact; the action is particularly effective on edges with corners that will be rounded and/or chipped. After this, special finishes can be performed such as grinding with hand tools in order to generate hollows and accentuate the worn effect. Subsequently a machine brushing or with manual conduction tools is usually performed for an uneven effect. Finally, wax or specific products to give tone, protection or water repellency are applied. The most suitable stone materials to be antiqued are those with not high hardness and the products obtained have wavy and smooth surfaces to the touch that find multiple applications for their particular aesthetic value.
Stone materials commonly processed by antiquing:
TRAVERTINE / MARBLES and CALCAREOUS STONES
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