Petra, restoration and reconstruction of old stone architectural elements

Restoration and reconstruction of old stone architectural elements

Masters in restoration and reconstruction of old stone architectural elements

Tradition, innovation and artisanal knowledge are the foundation of Petra srl: passed down experience and knowledge inspire our work. We use historical methods and tools, the chisel and wood mallet, avoiding the use of machinery or standardized elements. The manual labor renders each piece unique and imbues within it the local history, skills and centuries of experience. The sublime imperfections invoke the memory of Michelangelo and the millennials-old battle between man and stone.




Limestone restoration pietra serena stairs

The strong historical tradition of stonework in the city of Firenzuola (east of Florence) is expressed by Petra srl into classical work, for both public and private clients, to produce stairs, door frames, urban elements such as pavements, and internal and external decor.



Stone reinassance fireplace

Tradition is combined with innovation, conservation, improved manufacturing techniques and the development of new technologies and services. With an eye toward the challenges of the future, Petra combines traditional experience with an innovative spirit.











Petra srl is a team of three stone masters specializing in the restoration of classic and antique stone elements, both decorative and architectural. During a conservative restoration, we reconstruct architectural elements in historic buildings and residences. Our laboratory is located in Firenzuola in the province of Florence.



Limestone architectural fittings Limestone architectural fittings

 



WHAT WE DO





Custom Projects


We work with pietra serena sourced from Firenzuola's historic quarries to create various architectural elements based on your design or to match any style: from fireplace mantles and balustrades to stairs and window sills, thresholds, and engraved plaques for office buildings. Pietra serena is an ideal material for many projects, both luxury and commercial.




History and Tradition


Pietra serena is a type of sandstone that has been used in construction since the Etruscan era. Throughout the centuries, examples of its use can be found in architectural and artistic works. Most pietra serena originates in the areas surrounding Firenzuola, so much so that it is also referred to as Pietra di Firenzuola. Quarry work and the subsequent phases of production have traditionally been the main economic activities of the area.




Conservative Restauration


Given our close proximity to the Renaissance city of Florence, we specialize in the conservative restoration of historical buildings and in the reconstruction of antique objects, decorations and decor, both external and internal. We also collaborate with stonecutters and sculptors for cutting and finishing stones and, in the case of artists, for executing their works of art.





lavorazione e manufatti pietra serena ricostruzione manufatti in pietra ed elementi architettonici




CHESS BOARD IN BLACK AND WHITE MARBLE
REBUILT OF AN ANCIENT STONE WASHBASIN
RENAISSANCE FIREPLACE REBUILT
TABLE LEGS IN TRAVERTINE STONE
REFURBISHMENT OF AN OLD CHURCH FACADE
ANCIENT STAIRS REBUILT
ARCHITECTURAL STONE SHELF REBUILT
STONE FIREPLACE ON CUSTOMER DRAWING
OLD STONE CHURCH TYMPANUM REBUILT
ANCIENT WINDOW FRAME REBUILT
BAS-RELIEF SACRED IMAGE ON DRAWING
LIMESTONE HERALDIC EMBLEM ON DRAWING





History and Tradition, the Use of Pietra Serena in Antique Cities



Activities surrounding the extraction of pietra serena have been carried out in Firenzuola since antiquity and before historical record keeping. Initially it was a parallel and complementary activity to agriculture. With the latter producing very modest incomes, given the orographic characteristics of the soils, dual employment in stonemasonry and agriculture was very widespread in the area, following the rhythms imposed by the seasons. The field was cultivated with the heat, and stone was worked in the winter. This humble activity was made possible by the presence on-site of a raw material suitable for excavation and processing: the area, rich in sandstone, is in fact endowed with an outcropping of the geological formation known as "marly-arenaceous," which manifests as homogeneous and continuous banks or rows. Today the extraction and transformation of pietra serena is by far the main activity in the area, but it has also assumed an important and strategic role at the national level as it is the only industrial center existing in Italy for the extraction and processing of pietra serena.

Located along an important route through the Apennines, Firenzuola has played a strategic role since its founding. Equipped with defensive structures adapted for hospitality and to offer refuge, it assumed an important role for the movement of people and goods and acted as a strategic bulwark for Florence from its establishment in the year 1373. The town is situated along a central axis that connects two principal centers, Florence in the South and Bologna in the North. The midpoint of this route opens to the central, rectangular piazza and fortress. Pietra serena has been used locally since antiquity as a construction material, hammered out or squared off into blocks, as slabs applied as facades and for accessory objects used in dwellings: wash basins, thresholds and staircases.

Stone extraction and finishing activities have existed since the settlement of the town. During this era, defensive walls made of rectangular blocks were constructed from local stone. Repairs and modifications dating to subsequent eras, between the end of the 1400s and the beginning of the 1500s, are also visible. The fortress that is now the site of City Hall was excavated to build the Museum of Pietra Serena below. During this excavation, antique walls designed by Sangallo were uncovered, with two entrances, one leading to Florence and one to Bologna. In the 1700s, the opening of a new road through la Futa moved the main artery connecting Tuscany and Emilia Romagna, and new construction of inns, taverns and post offices proliferated along this road, using almost exclusively pietra serena. An important project completed during the 18th century was the Antica Dogana Granducale Le Filigare, which was recently converted to be used as a conference center by a private company, and at which the skilled manual artistry of the old stoneworkers can be admired.

Traces of this work are still visible in the area. In some antique quarries, writings from the 17th century have been discovered. These are mostly not true quarries as one would imagine today, but activities conducted on outcropping layers of stone, from which, with the rudimentary equipment of the era (mallets, stone splitters, chisels), the block was cut into the required dimensions and finished directly on-site to obtain the desired form and finish. Extractions were limited to the quarries located nearby the city centers, since the difficulty of transporting the heavy stones strongly favored their use locally, especially when located in less accessible areas.

The activity remained modest until after the second world war, when, in the 1960s, two important projects expanded the use of Firenzuola's pietra serena: the German War Cemetery located at Passo della Futa and the reconstruction of the Church of San Giovanni Battista in the center of Firenzuola. The latter project was the product of the architects Carla Scarpa and Edoardo Detta. During this time, activities relating to the extraction and finishing of pietra serena underwent a radical transformation. Before this, the stone work activities were more or less artisanal in nature. They then transformed into small companies, and the first mechanical cutting facilities and risers for the cutting and transformation of blocks into slabs were installed. The companies, supported by a growing market demand, invested in the acquisition of the first mechanical means of extraction. Quarries that were previously impossible to reach became accessible and usable. Access roads were built into new cultivation zones, and the foundation was laid for the consolidation of extraction zones that continue to provide blocks to the current modern excavators to this day, and are expected to continue to do so for much longer in the future.

The finishing laboratories for transforming semi-finished stones or slabs into finished products also underwent a radical transformation with the birth of new and modern factories along the banks of the Santerno river, with the adoption of fully mechanized processes for stone cutting and finishing. From a few thousand cubic meters extracted in the 1960s (an estimated 5,000 CBM were extracted in 1965), current production is at 80,000 CBM.

The increase in stone extraction and the expansion of the finishing activities have caused a series of problems over the years relating to the environmental impact: the storage and disposal of the resulting materials and the processing and settling, or purification, of the water used in stone cutting. The environmental impact is a high price that must be paid for the extraction of the stone needed for the restoration of the artistic legacy of our cities, Florence, Siena, Arezzo to name a few.

The great wounds inflicted on the mountains represent the strength of man but also his weakness. Over the years and through a succession of cultivation plans, the extraction zones have become concentrated in two basins, Brento Sanico and Rovigo, which are decentralized and inconspicuous zones. The other quarries, along the path of the Santerno river and the road to Imola, have been closed and restored. Building on other experiences in Europe and Italy, plans are being made to employ alternative solutions to reuse these locations to promote culture and increase environmental value, with a pilot project at the Bagnatoio quarry. The large waste disposal sites, containing waste materials from the old quarries, are being cleaned up, and the materials recycled as raw materials for other production processes. New waste disposal sites will not be formed, and all resulting materials will be recycled.

he problem of treating the water necessary for cutting work has been resolved with a commendable solution in the production of a centralized plant for the industry. This is the only example in Italy of a centralized purification facility for the treatment of water used in stone cutting: the dehydrated mud resulting from the treatment is sent for recycling, thus closing the circle of the waste disposal process. Alongside the industrial activities, a more artisanal type of finishing remains. Again in this case, the stoneworkers, in addition to continuing to create projects based on traditional models, have developed initiatives aimed at researching new formal solutions in the field of design objects and urban design.

The opening of the first part of the Museum of Pietra Serena in the historic fortress of Firenzuola set the stage for the conservation and appreciation of the town's deep historical knowledge. The work of the stonemasons, passed down from father to son, has left a legacy over the years that can still be found in the coats of arms that adorn the main buildings or in the peace of the ancient cemeteries.

Times have changed, but the familiar relationship between the quarryman and stone remains. The most significant rows of stone are still known by name. Some of the most historically significant are referred to as "the eaves," "the manhole covers," "the monument," "the doors," "the staircase," "the good rock," or "the big rock," the latter of which is more than three meters wide, and the "big fatty" and "little fatty", known for their size.


[ "Pietra Serena Materiale della Città" (Pietra Serena Society of Firenzuola), Consorzio Pietra Serena di Firenzuola, Edition AIDA 2002 ]


Pietra Serena Surface Finishing



The high workability of Firenzuola's pietra serena allows for a number of surface finishes. These are principally divided into four types: impact, pressure, thermal and abrasive finishes, depending on the type of surface desired and the end use of the stone.

The impact finishes are obtained by using percussion or pneumatic instruments or by hand. Of the countless effects that can be given to Firenzuola's pietra serena, the most common are bush hammering, hammering, furrowing, and chiseling.

Bush hammering is one of the most antique rustic finishes because it renders the surface of the stone very similar to that of the raw material, highlighting and revealing any crystals and veining. Bush hammering is performed with a bush hammer, a mallet with small, raised pyramidal points. This was previously done manually, but is performed today by a machine operating on risers. This finish confers a particularly sculpted, rough and textured aspect to the stone. The result is particularly adapted for external use, such as stairs, curbs, and pavements as it reduces slippage. It is also appropriate for exterior facades when combined with other types of finishes.

Hammering is the most ancient of the surface finishing techniques: it is considered by many as a variation of bush hammering since it results in the creation of contrasting visible and chromatic elements and even relief effects. It is common to find hammered surfaces on exterior facades. The hammered effect is achieved with a chisel and mallet, and there are now pneumatic hammering machines.

Furrowing is a type of surface finish that lends itself to be used on both raw and semi-finished stone, but also on products that have already been honed or even previously bush hammered and/or flamed. It is a type of finish that is particularly adapted to outdoor pavement, but it was previously also used for traditional external facades. Furrowing was done in the past by hand with a mallet and chisel; today saws and diamond-plated discs are primarily used. Furrowing consists of making incisions of lines more or less 8 to 15 mm wide, of varying depths that range between 2 to 5 mm. In specific cases such as paved vehicle roads on a steep gradient, the furrowing can reach up to 10 mm deep with distances between one line and another reaching between 8 to 15 mm. One type of fine striation that is more closely spaced and irregular is achieved with a claw chisel and is known as "combing".

Chiseling is perhaps one of the finishes that is best known both because it is one of the most common and because it is one of the most simple. Many roadway pavements still use to this day this type of finishing, which, in some cases, is still done by hand by the stoneworkers directly on-site.

The impact finishes of bush hammering, hammering, furrowing and chiseling can be distinguished based on the level of incision of the surface. Rustic grained surface finishes generally have chisel or bush hammer indentations with a depth varying from 8 to 12 mm (large gauge). Surfaces finished by machine to a medium gauge generate indentations with a depth of 5 to 8 mm (the most common) and are classified as medium grain. Fine grain finishes instead have indentations with a depth that varies between 2 to 5 mm.

The pressure finish used on pietra serena is known as sandblasting. With sandblasting, the surface takes on a roughened, yet never sharp, aspect. This results in a finish that is often soft and relatively uniform and that can be found in external facades and low relief work (writing, drawing, carving) as some of the more common applications. The effect is obtained by projecting an abrasive mix composed of water and sand or other hard material at high pressure and velocity. Sandblasting is also used as a cleaning treatment to remove any scaling that may form on the surface, for example, on exterior facades. Sandblasting, like the impact finishes, can also have various degrees of depth, although too high an intensity is generally not used so as to avoid excessive wear to the surface layer.

The thermal finish that can be used on pietra serena is called flaming, which creates a surface verification effect that yields a roughened (but never sharp) and glassy aspect to the stone, with a characteristic chromatic effect. This is obtained by flaming the stone at high temperature. Flaming does not change the color of the surface, as with impact finishes, so much as the surface grain. This finishing treatment can increase the resistance to chemical aggressions and surface erosion, but alters the resistance of the material over approximately 3 mm of depth. It is used both for external facades and where a high degree of traffic is expected.

Of all the abrasive finishes, the only one used for pietra serena is honing. Honing attenuates the color of the stone, provides optimized planarity to the surfaces, yet does not create a mirror effect typical of polishing, which cannot be obtained on this material. Previously, this type of finishing was used for internal facades and internal pavements. More recently, however, it has found wider use with the evolution of external facade mechanical mounting systems.

Especially for elements that will be used outside or under harsh conditions, additional specific finishing treatments can be used. These treatments principally involve water repellants that allow the pietra serena to better resist aggression from water or toning applications that return the finished stone to its original darker shade that may have been altered during other finishing procedures.


[ "Pietra Serena Materiale della Città" (Pietra Serena Society of Firenzuola), Consorzio Pietra Serena di Firenzuola, Edition AIDA 2002 ]





conservative restauration, reconstruction of antique objects of old stone elements conservative restauration, reconstruction of antique objects of old stone elements





CONTACT PETRA SRL


Petra Srl

Via Cornacchiaia Alberaccio 389
50033 Firenzuola, Firenze, Italy
Ph. +39 3383491482 / 3381881827 / 3394691784
Email: info@petrafirenzuola.it
Web: www.petrafirenzuola.it



Marco Galeotti
Alessandro Conti
Davide Conti






PETRA SRL

Via Cornacchiaia Alberaccio 389
50033 Firenzuola (Firenze)
Italy

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