Ashlar surface

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The stone surface is the result of the extraction and processing of stone .

When artificial and natural stone is processed for use as a building material, art object or commodity, it is called ashlar . The processing stone creates the surface of the stone .

Quartzite Azul Macaubas , polished

Since the beginning of the 20th century, natural stone surfaces have generally been machined. However, certain surface structures are still produced with hand tools. Traditional methods of processing are taught in the craft training to become a stonemason and are used in particular in monument conservation.

The surface treatment can have a decisive influence on the visual effect of natural stone . Due to the influence on the refraction of light , textural , structural and colored features of the rock often appear much more intense and clearer after polishing. With the help of coatings such as stucco marble or joint painting , the visual effect can be fundamentally changed. In artificial stone , the surface can be carried archetypes make such a form skin or structural concrete .

When designing stone-transparent surfaces on buildings, both inside and outside, the visual effect as well as the resistance to weathering, wear and tear and chemical cleaning agents are important. With stone floors, slip resistance and cleaning costs are also important.

Traces of historical tool processing with clearly recognizable signs of weathering

Rough machining

Coarse processing techniques such as sharpening, scraping and hatching find and were used as historical stone processing methods in and outside of buildings. Flamed, sandblasted or bush hammered stone surfaces are stone working methods of modern times. These types of processing are used outside of the building, only in exceptional cases inside. Honed stone floors were only used by wealthy builders in the past. In simple historical buildings there are often rough stone surfaces that make cleaning difficult.


Rustic masonry with rough embossing cuts and edge chipping

Bossed stone surfaces exhibit on their surface a few strokes of the Bossiereisens , resulting from the fact that earlier in quarries Rohsteine in its outer shape with a so-called break inch (about 3 cm supernatant) were cut. Of the split stone surfaces the big supernatants were also Bossierhammer (today Sledgehammer ) and flatter abbossiert or knocked off. The term Bosse is Middle High German and means to beat. The embossing hammers were available in the size of a mallet to a large hammer, depending on the purpose .

Bosses were often given a border to emphasize the stone format and to structure the area.

Bounced and blown up

The surface treatment named in DIN 18322 bruised shows a view that is created by blasted or chipped stone outer edges. The explosive iron is placed on the edge and hit the tool with the hammer to cut off pieces of stone that have the shape of a shell. This processing is mostly referred to as blown up . Bouncing is either done in preparation for further manual surface processing or, for example, in order to provide bricks with a very uneven surface structure.


Sharpened stone surface made of sandstone
Pointed surface made of Beucha granite porphyry , pattern approx. 25 cm × 15 cm

With the bifurcated or from sledge hammers driven chisels a rough stone surface is leveled. Depending on the number, distribution and depth of the cuts on the stone surface, a distinction is made between coarse and fine-pointed, although the boundary between the two forms of processing is not precisely defined. Pointing is a manual machining process, usually in preparation for a subsequent use of tools, such as a toothed iron , a surface or a mallet . These tools leave visible punctiform indentations in the surface, so-called pointed cuts. According to the arrangement of the pointed cuts, a distinction is made between lane-pointed and point-pointed.


The surface, which the stonemason has previously roughly sharpened, is further leveled with the crown . The Krönel carries 10 to 15 pointed steel pins arranged in a row, which are fastened in a metal handle (so-called bottle) with a wedge. This tool, which was first used during the Renaissance , leaves small coved indentations in the stone surface. The technical advantage of crumbling sandstones lies in the minimized impact (shattering) of the binding matrix of the grains of sand, as would occur, for example, with the use of a mallet . In the case of bruised sandstone surfaces, the surface can weather in a shell-like manner. Today a crowned stone surface can be the finishing touch; But it can also be processed further and either sanded or scratched.


The sharpened surface is prepared with the toothed iron for further manual work steps, such as hatching or scraping. The toothed iron is only used on soft stone (e.g. marbles, limestone and sandstone) and is driven with a stick . Depending on the material and the effort, the teeth of the toothed iron leave indentations with a length in the centimeter and depth in the millimeter range. The main advantage of using a toothed iron is that the so-called pawn , the creation of undesirable depressions or holes in the stone surface, is largely avoided if the tool is held correctly. The tooth iron is a historical stone working tool that was used by ancient stone sculptors in Greece. It was not used again until the Gothic period.


Carved stone surface from Obernkirchen sandstone , pattern approx. 25 cm × 15 cm

With a stone ax , juxtaposed cuts are made on stone surfaces. The cutting width of a hatchet is about four centimeters; the blows leave notches or grooves in the stone (see illustration). The stone ax, which has a soldered hard metal piece in the cutting edge, is mainly used today for the surface treatment of gravestones and is successfully used on all soft stones such as marbles, sandstones and limestones.


The stone ax used today comes from the Romanesque period . It is used to level rough stone and is therefore called a surface . The area has a working width of about ten to twelve centimeters. Nowadays it is still used in various ways when processing limestone and sandstone. In the Gothic style , the edge width of the surface was reduced to up to three centimeters. With this virtuoso, complicated profile shapes of the Gothic buildings were "hewn out". Karl Friederich calls this tool in his book on the stone working pill and the corresponding surface Pillung .
Sharpened surfaces are often confused with chipped surfaces. The difference can be seen in the fact that scratched surfaces do not have triangular recessed notches, but fillets or grooves.


Scraped stone surface made of sandstone
Machine-scratched stone surface made of Obernkirchen sandstone , pattern approx. 25 cm × 15 cm

With bush hammer look like wide chisel, building stones be finished by stonemasons. All previous work processes, such as sharpening and teething, must be completed. The chisel blades have different blade widths and are referred to by experts as quarter or half blades. From a width of about eight centimeters, we speak of a sharpening iron. Scraping requires perfect tool guidance, which requires long practice. The blows are applied in parallel and must be struck with almost the same amount of force with the aid of a club . The stonemasons put auxiliary lines on the stone beforehand to achieve parallelism. There are two types of scratched surfaces, right-angled in lines and the so-called colored scratching. Chisel blows at a 60 ° angle to the outer edge are called Gothic . In the case of colored scraping, the parallel cuts are used squarely according to the width of the cutting edge. By changing direction in the squares, a checkerboard-like pattern is created. More recently, machine-made scratched surfaces have been offered by stone factories. However, the result of this machine work is visually unsatisfactory.

Chisel cuts can only be carried out optimally if the stone surface has been handcrafted beforehand and a rough material overhang in the millimeter range can be worked off on the surface. The stonemasons say: “We need stone material to scrape before the iron.” In the case of surfaces made with circular stone saws , the chopping cuts cannot be carried out accordingly because the rough material overhang is missing. In this case, stonemasons speak of "stilting" or "stilting" when scraping.

Scharriereisen was introduced in Germany in the middle of the 15th century. It was only two inches wide at the time. It was not until the Baroque and Rococo that up to 16 cm wide buckles were used. The scraper blows are no longer noticeable at some distance. The impression of smooth surfaces is created. Up close you can see that the chisel iron creates fillets in the stone surface. In the Baroque period , the stonemasons invented scarfing cuts that left throats or grooves up to the size of a thumb in the shape of segmental arches. Several blows were carried out in a special tool posture. Today they are known as the Hamburger Bauhau .

Free of the blow

Free of the cut means that the tool tracks in the soft rock run without direction and are hardly recognizable as cuts. After the preparatory manual stone work, such as B. the teething, a largely flat surface is produced by using the hinge with a flat bevel to smooth out stone protrusions and to remove previous machining marks. The stone surface can be produced with flatness tolerances of less than one millimeter by continuously checking it with a straight edge.

A stone surface that is free from the cut can then be optimally scraped.


Bush-hammered stone surface made of Beucha granite porphyry , pattern approx. 25 cm × 15 cm

Bushing of stone surfaces was originally a classic artisanal surface processing for hard stones (e.g. granite , syenite , granodiorite ), which were shaped in manual work processes from rough to fine before grinding and polishing with stone grinding machines . A mallet , the work surface of which looks like that of a kitchen meatbeater with pyramid-shaped teeth, is used to create stone surfaces with different rough edges. Differences in roughness are determined by the size of the teeth and thus the distance between the rows of teeth:

  • Roughly bush hammered: Tooth sizes 10 to 12 mm
  • Medium stacked: Tooth sizes 6 to 7 mm
  • Finely stocked: tooth sizes 4 to 5 mm
  • Finely bush-hammered and ready for grinding: tooth size 4 mm
  • Finely stocked: tooth size 3 mm

Bush-hammered surfaces don't shine; they are rough and dull. Stone exterior coverings can be equipped or retrofitted to prevent slipping by hammering. The use of hammer hammers on marble and sandstone is frowned upon by experts. (See above under pointed .)


For optical reasons, the stone surface is often hit with a corrugated hammer, the working surface of which does not have teeth like those of a mallet, but rather several triangular blades made of hard metal next to each other. When corrugating, the cutting edges meet the stone surfaces and a directed, striped surface structure is created as a finishing touch. The Riffelhammer is two-handed and can only be used on massive stone, as stone slabs would be at risk of breaking.


Flamed stone surface made of Serizzo , a gneiss , pattern approx. 25 cm × 15 cm
Manual creation of a flame-treated surface

When burning natural stones, smooth stone surfaces are roughened with an acetylene - oxygen burner. Natural stones consist of a mixture of anisotropic minerals which, when the temperature changes in different spatial directions, expand to different degrees and thus break. The mineral pyroxene , for example, expands very strongly in one of the three spatial directions when heated. When the Impala is flamed, this leads to the surface melting and bulging. With quartz , there is a sudden increase in volume at 573 ° C, which leads to intensive flaking. Therefore, operators wear a face mask when manually applying flame with the flame lance.

In principle, all hard rocks can be flamed. This creates a relatively uniform, rough surface structure. Caution is advised when flaming yellow granites, as the yellow iron oxide ( limonite ) can be converted into red iron oxide ( hematite ). The stone surface is roughened, but yellow becomes red or reddish granite. Therefore, yellow granites are usually not flamed. Belgian granite , a limestone from Devon , and some containing quartz sandstones are exceptions that can be flamed.

Flamed surfaces are characterized by excellent slip resistance and are therefore primarily installed outdoors as non-slip surfaces. In contrast to sticking, there is no controllable gradation from coarse to fine for flamed surfaces. The result of the flaming depends on the type of natural stone, the minerals it contains and the temperature jump that occurs when flaming. This can be increased in industrial series production by cooling the heated surface with water.

Natural stones that have already been built in, which are too sensitive to be bushed afterwards, can often be roughened by flames.


Sandblasted stone surface made of Ruhr sandstone , pattern approx. 25 cm × 15 cm

The surface is processed with sandblasting devices and abrasives of different pressures and grain sizes. Depending on the blasting material, blasting pressure and rock composition, a coarse to fine surface can be created. Quartz sand is no longer used as blasting material, which can lead to silicosis when blasting , but quartz-free materials such as corundum .


In the past, rocks were sanded to grind or prepare a polish. This physically difficult work was still carried out in the post-war years by manual grinding using various types of sand that were rubbed over the surface with a special steel block.

Today sanding is carried out as surface treatment with stationary articulated arm grinding machines using a grinding wheel made of steel and quartz sand. Sanding creates a matt and relatively smooth surface that is non-slip indoors, but is often not rough enough for outdoor use. The roughness of sanded surfaces is comparable to a C 30 to C 60 cut (see below).

Gap rough and sanded

Gap-rough surfaces are produced with stone tools and show unprocessed (natural) stone surfaces. Gap-rough surfaces are used either as masonry stones, facade panels or floor coverings. When installing split natural stone, you should pay attention to the marks left by stone splitting tools, such as wedge holes. Slate rocks are mainly used for indoor floor coverings with rough cracks , e.g. B. Alta quartzite or fissile limestones such as Solnhofen slabs are used. When laying rough-split natural stone slabs outdoors, care must be taken to ensure that the gradient is sufficient so that the water runs off the often uneven split slabs reliably.

Natural stone slabs are also offered as rough and sanded , whereby they have been partially sanded with a sanding machine. This creates a stone surface that has both rough-cracked and smoothed areas.

Tumbled, antique

Tumbled or antiqued floor coverings made of natural stone are panels that have already been sawn to size and placed in a free-fall mixer with the addition of quartz sand and water. When the mixing drum rotates, the plates rub against each other and the stone edges are rounded. Depending on the grain size of the added material, the stone surfaces are bruised and rough or rounded and smoothed. The process can give the stone slabs an antique look.


Stone surface made from Obernkirchen sandstone with a circumferential cutter , pattern approx. 25 cm × 15 cm
Ground stone surface made of Beucha granite porphyry , pattern approx. 25 cm × 15 cm
Polished stone surface from Serizzo , pattern approx. 25 cm × 15 cm
Lasered stone surface made of granite , pattern approx. 10 cm × 10 cm

Milled surfaces are made with stone circular saws . Instead of a saw blade, a so-called peripheral milling cutter is used. Circumferential milling cutters are approx. Four centimeters wide and equipped with hard metal disks in which small artificial diamonds are worked. When using the circumferential cutter, groove-shaped tracks (see illustration) are created in the width of the cutter.



Manual grinding

Processing with abrasives is one of the oldest forms of processing for natural stones. Grinding used to be hard physical work that had to be carried out without the use of machines. The stone surface was finely ground with grindstones and various types of sand in monotonous work with one-sided physical movement and stress. Finally, the stone surface was given a high gloss by using "classic soaps" and beeswax.

JW v. On the occasion of a visit to Berlin in 1828, Goethe describes the introduction of mechanical processing methods: “ They began [...] to split large attachments and to work on column shafts from the pieces [...] which were made possible by going back for processing and after the machines operated. The two master stonemasons Wimmel and Trippel have so far excelled in this work. ” The stonemason Erhard Ackermann is considered to be the inventor of granite grinding technology .

Grinding today

Today, modern stone grinding machines with rotating grinding wheels and abrasives are used for grinding . There are mineral abrasive grains or diamonds in the grinding wheels. There is no easy way to accurately determine the surface roughness after grinding. The cut is z. B. marked with C 120 . The C stands for Carborundum (silicon carbide), the number stands for the grain size and is given in the mesh unit customary for abrasives . The resulting surface finish depends not only on the grain size, but also on the type of natural stone processed and the technology used. Articulated arm grinding machines can produce different results than automated grinding lines or hand-held grinding machines . The properties of the abrasive, the binding agent and the sharpness of the abrasive grain must also be taken into account. The micro-roughness and slip resistance vary significantly depending on the material, even when using the same grinding tool.

Even finely ground stone surfaces show grinding marks in the backlight. Depending on the mineral composition and distribution, significant differences in gloss cannot be avoided. Ground surfaces have the advantage that the surface can simply be ground again if necessary if signs of wear are visible (creeping smoothening) or to compensate for installation errors (so-called over-teeth).

Comparative Table: sanded, polished, and with the laser machined

Abrasive grit Machining Surface appearance
C 30 very coarse clear grinding and sawing marks, stone color and texture hardly recognizable
C 60 rough Clearly palpable grinding marks, stone color and texture hardly recognizable
C 90 medium Grinding marks visible from above, very pale colors, rough stone textures recognizable
C 120 medium Clearly visible grinding marks in the sidelight, pale colors, stone texture recognizable
C 180 medium to fine a bit smoother when attacking, otherwise like C 120
C 220 finer cut Stone colors and textures clearly visible, grinding marks visible in the sidelight
C 320 semi-gloss surface Grinding marks still visible in the grazing light
C 400 semi-gloss surface Biotites already shine, the color is easy to recognize, grinding marks are still visible in the grazing light
polished and lasered partially polished optimized surface, laser structure recognizable in the grazing light
C 600 almost polished optimized surface, grinding marks still visible in the grazing light
C 800 depending on the material Polishing effect depends on the material, grinding marks are mostly still visible in the sidelight


Not all stone surfaces can be polished.

Hard stones such as granite , basalt or gabbro can be ground out to such an extent that no grinding marks can be seen, not even in sidelight. However, there are differences in gloss between the individual minerals (especially biotite ). B. recognizable in granites. Therefore, there is no real polish here , only a partially polished surface.

On soft limestone such as the Solnhofen slabs , only a matt polish can be produced by fine sanding . A real polish can be created on marble and limestone with the help of oxalic acid or clover salt . Calcium oxalates , which reflect light particularly strongly, are formed on the surface of the natural stone .

The disadvantage of a polished or partially polished surface of the floor and staircase is the inadequate slip resistance. Slip resistance values ​​(e.g. R 9) are required in public buildings and workplaces. One advantage of the polished surfaces is that they are easy to clean.

Polished and lasered

With the laser technology for natural stone, invented by the Fraunhofer Institute for Laser Technology in Dresden, the surface can be processed both in the factory and after laying, e.g. B. to achieve slip resistance values ​​according to DIN 51130. Up to now, however, mobile laser devices are rarely used. Depending on the material, an optical influence on the appearance is to be expected. The process increases the slip resistance through micropores burned into the surface. The gloss of the polished stone surface is largely retained. Depending on the cleaning process, the slip resistance is retained in the long term. Compared to chemical etching, there is no risk of discoloration of the stone. Due to the higher costs, conventionally matt-ground stone surfaces are currently still predominantly used, but they are more difficult to clean.

Polished and microblasted

In the micro-blasting process, micropores are mechanically blasted into the polished surface in order to achieve slip resistance in accordance with DGUV rule 108-003 (formerly BG rule 181 / DIN 51130) in the commercial sector or in accordance with GUV-I 8527 (DIN 51097) in wet barefoot areas . In contrast to laser technology, the micropores are not grid-shaped, but rather scattered and introduced into the surface without any recognizable direction, otherwise the results are similar.

Chemically etched

With an etching by acids, the stone surface may be processed at the factory or after the installation of the floor covering, in order to achieve the evaluation of the slip resistance group R 9 in accordance with DIN 51,130th The chemical application can only be carried out by specialists. The etching of the stone surface can not only impair the appearance but also cause discoloration in the installed floor. When using hydrofluoric acid , which is able to etch quartz in hard rock, special occupational safety measures must be taken for the personnel because this acid is highly toxic. A sandblasted and etched surface came onto the German market from Australia under the name Bright Etched . It could only be purchased as directly imported goods and was hardly in demand.

Flamed and brushed

Floor coverings in particular have been increasingly flamed and brushed since the turn of the millennium. In the production plant, the rock surface is first roughened by flaming (see above). The rough surface is smoothed again with the help of steel brushes or plastic brushes fitted with abrasive grit. Since the bristles adapt to the surface, however, only the crystal edges created by the flame are broken and smoothed, while the slight waviness of the surface remains. The surface feels velvety soft, but is macrorough .

Jet blasted

This relatively new processing is not normatively defined and every manufacturer produces its "jet radiation" with water and abrasives in its factories. The surface that is created in this workflow is to be compared with the brushed surfaces (see above).

Edge processing

The respective surface processing corresponded to the edge processing. In addition to right-angled edges, there are profiled edges such as bevels , round bars , covings and also multi-composite profiles.

Stone surfaces and slip resistance

According to the German trade association rule (BGR) 181, minimum requirements apply to slip resistance in public spaces . The slip resistance values ​​range from R 9 to R 13:

  • R 9 for interior floor coverings in general areas (offices)
  • R 10 for public toilets
  • R 11 for shop entrances and stairs outside as well as in kitchens for communal catering in dormitories, day care centers, sanatoriums
  • R 12 for hospital kitchens and kitchens in which more than 100 place settings are provided daily
  • R 13 for floor coverings in slaughterhouses

In swimming pools and saunas, letter values ​​apply:

Assessment group Application example
A. Locker rooms
B. Shower rooms
C. Walk-through pool

Freely designed stone surfaces

Since the 1960s, stone designers have deviated from the traditional rules of stone processing. A rational workflow traditionally followed the principle of going from rough to fine . In the case of hard stone in particular , the stone surface was first sharpened and smoothed with ever finer hammers and then polished.

Today stone surfaces are also freely processed, with the processing sequences being carried out individually according to the artistic eye of the artist, who aims at the design optics and effect.

For example, a stone surface is first bush hammered, then sharpened and finally polished. Under certain circumstances, it is not the entire stone surface that is polished, but only individual parts, which results in partially polished and partially rough surfaces.

The free surface design can often be found on sculptures , designed stone walls and artistically or handcrafted gravestones.

Guidelines and standards

  • Germany
    • DIN 18332 Part C: General technical contract conditions for construction works (ATV); Natural stone work
  • Austria
    • ÖNORM B 2213 Stone masonry and artificial stone work - work contract standard
  • Switzerland
    • Standard SIA 118/246 General conditions for natural stone work
  • Europe
  • Terms and definitions:
    • EN 12670 natural stone - terminology
    • EN 12440 natural stone - criteria for the designation
  • Test standards for natural stone as floor coverings:
    • EN 1926 test method for natural stone - determination of compressive strength
    • EN 1936 Testing of natural stone - Determination of the true density, the bulk density, the open porosity and the total porosity
    • EN 12371 Testing of natural stone - Determination of frost resistance
    • EN 14157 Test method for natural stone - Determination of the resistance to wear
    • EN 14231 Test method for natural stone - Determination of sliding resistance with the aid of the pendulum tester
    • EN 1341 Natural stone slabs for outdoor use - Requirements and test methods
    • EN 1343 Natural stone curbs for outdoor areas - Requirements and test methods
  • Product standards:
    • EN 12057 finished products, tiles
    • EN 12058 floor slabs and step coverings

Tools for making stone surfaces

The following shows the stonemason's tools, which are used to produce natural stone surfaces.


  • Hans-Peter Autenrieth: About the fine relief in Romanesque architecture. In: Franz J. Much (Hrsg.): Architecture of the Middle Ages in Europe. Hans Erich Kubach on his 75th birthday. Stuttgarter Gesellschaft für Kunst und Denkmalpflege, Stuttgart 1988, ISBN 3-926168-00-5 , pp. 27–70.
  • Carl Blümel : Greek sculptor at work. 2nd Edition. Walter de Gruyter, Berlin 1941.
  • Herbert Fahrenkrog: Natural stone in everyday life. Questions and answers. Callwey, Munich 2007, ISBN 978-3-7667-1729-0 .
  • Herbert Fahrenkrog: Floor coverings made of natural and artificial stone: laying technology. The practical book for planners, stonemasons and tilers. Callwey, Munich 2001, ISBN 3-7667-1457-0 .
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  • Karl Friederich : Stone processing in its development from the 11th to the 18th century. Filser, Augsburg 1932. At the same time: Karlsruhe, Technical University, dissertation, 1929, (Reprint: Aegis, Ulm 1988, ISBN 3-924756-02-3 ).
  • Albrecht Germann, Kownatzki Ralf, Mehling Günther (ed.): Natural stone lexicon. 5th, completely revised and updated new edition. Callwey, Munich 2003, ISBN 3-7667-1555-0 .
  • Rosemarie Klemm , Dietrich Klemm : The stones of the pharaohs. State Collection of Egyptian Art, Munich 1981.
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Web links

Individual evidence

  1. Otto Herrmann: Quarry Industry and Quarry Geology . Borntraeger, Berlin 1916, p. 251
  2. ^ Richard Thiele: Stone masonry in architecture. Fachbuchverlag, Leipzig 1957, pp. 21/22.
  3. ^ Karl Friederich: Stone processing in its development from the 11th to the 18th century . Filser, Augsburg 1932, p. 66.
  4. A descendant of Wimmel founded one of the largest stone industry companies in Germany, the Zeidler & Wimmel company, which still exists today .
  5. Festschrift: 175 Years, Zeidler & Wimmel. 1776-1951. Zeidler et al. Wimmel, Berlin et al. 1951, p. 8f.
  6. Caution, danger of slipping. Process to increase the slip resistance . Stein trade journal, Callwey Verlag Munich, edition 10/2009.
  7. Expert discussion or advertorial in FZ Naturstein . EbnerVerlag, edition 8/2008, p. 17.
  8. See also the corresponding DGUV test certificates.
This version was added to the list of articles worth reading on February 3, 2008 .