THE “PIETRA SERENA” STONES OF BRUNELLESCHI’S CUPOLA · by Brunelleschi, Michelangelo and...
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THE “PIETRA SERENA” STONES OF BRUNELLESCHI’S CUPOLA Coli Massimo 1 , Tanini Chiara 1 , Haines Margharet 2 , Nenci Cinzia 3 , Federica Bencini 1 1 Dept.of Earth Science, University of Florence, Italy – 2 Harvard University “Villa i Tatti”, Florence, Italy - 3 Dept. of History of Arts, University of Florence, Italy The Cupola of the Santa Maria del Fiore (Florence Cathedral), was vaulted by Brunelleschi in the years 1420-1436. From 1417 Brunelleschi participated in the competition for the methods of the realization of the vast Cupola (planned from 1368), and in a document dating 1420 he explained how and with which materials it would be erected. The Cupola was built without any centering from the ground; it was self-sustaining with only a light working scaffolding at the top of the building as the construction proceeded. In order to solve the problem of how to vault the Cupola, Brunelleschi introduced new techniques and a selected and focused use of building materials. For the supporting masonry Brunelleschi required Pietraforte, a quartz-carbonate turbidite quarried in the hills south of Firenze. The vaulting-ribs were built in Carrara marble; the bases of the eight vault segments were made of Pietraforte and continued upwards with special sized bricks in a herring-bone pattern. The outward thrusts of the Cupola are contained with chains of a specific type of Pietra Serena, which was quarried at the Trassinaia quarry. The archives of the Opera del Duomo (www.operaduomo.firenze.it/cupola ) show that particular materials were chosen for specific uses, and in many instances the precise quarry where the stones had to come from was specified. The documentation online, edited with texts and analytic and structured indexes, contains information concerning the selection of quarries, their management by the cathedral work forces, the cutting and transport of stones and the quality controls at construction site. The sources present rich historical terminology for the description of stone types and their appropriateness to various structural applications. THE CUPOLA Hypothesis illustrating the disposition of the Pietra Serena stone beams of the first stone chain of the Cupola This stabilizing and binding structure is hidden within the Pietra Forte masonry of the base of the Cupola It is noteworthy that Pietra Serena was chosen for its tensile strength in this application, while Pietraforte needed only to respond to compression forces. As the Cupola rose, radially disposed bricks took the place of the Pietraforte masonry, but Pietra Serena continued to be employed for working architectural elements such as entablatures and binding elements. A looking up view to the wood chain, which was installed only on the first level and judged ineffective. On the basis of its performance in architectonic applications, which depends on the percentages of calcite and grain- package of the single beds, the quarriers were able to recognize different grades of Pietra Serena, the best grade being the Serena Gentile (Gentle Serena) which came from the cultivation of a few specific beds. It was widely used by Brunelleschi, Michelangelo and Vasari for some of the outstanding buildings in Florence. The quarrying activity of the Pietra Serena was established in the Fiesole hills, north of Firenze, by the Etruscans and last till the middle of the XX Century. Quarrying activity of Pietra Serena in the hills of Fiesole near Florence goes back to Etruscan times and continues up to the mid-XX century. Pietra Serena is the classical historical name given throughout history by the quarriers to the hewn stones cut away from the best-graded sandstone beds of Macigno in the area around Florence. Macigno is a silicoclastic turbiditic succession derived from the dismantling of the western-central Alps, which in the Oligcene period underwent strong uplift and erosion. Macigno was deposited like an elongated sub-marine fan into the Appennine fore-deep, at the top of the Tuscan sedimentary sequence. Macigno sandstone displays the typical Bouma sedimentary features and all the facies associations described by Mutti & Ricci Lucchi (1972) and Mutti (1992). Macigno was deposited syn-tectonically in middle-late Oligocene, reaching a thickness of about 3 km with a depositional rate of 30 cm/ky and a global volume of about 67.000 km 3 . Macigno displays different sedimentological characteristics from the bottom to top. THE PIETRA SERENA Authors subdivide Macigno vertically into two members: a lower Macigno s.s., typically outcropping in the Chianti region, mainly made of coarse-grained Ta, Ta-c amalgamated beds, and an upper Mt. Modino sandstone constituted by a rhythmic alternation of classic Ta-e beds and thin-bedded turbidite bodies. The Macigno sequence outcropping in the Fiesole hillside north of Florence is related to the topmost layers of the Mt. Modino member. Facies associations recognized in the Macigno in the Fiesole hills point to its formation in an outer- fan depositional environment, with stacked depositional lobes interbedded with interlobe and fringe of thinner beds. The whole sequence seems to be more proximal, thickening and coarsening upwards, in the uppermost part. The petrographic composition of the Macigno, with reference to the sandstone layers, is almost constant. It is a quartz-feldspatic greywacke with lithic fragments of mainly metamorphic origin; clay is present both as clast and matrix. Calcite is instead present in low percentages (max. 17%) constituting both clasts and cement. The physical and mechanical properties of Macigno coarse sandstone beds are on the average very good and justify uses for structural and ornamental purposes. Despite almost uniform sedimentological features, physical-mechanical properties and mineralogical composition, stones from different beds display great differences in operating performance, due to small variations of calcite and clay percentages and of grain size and grain-package. a b c d Pietra Serena used as ornamental stone in Florence: a) arcade of the Innocenti hospital by Brunelleschi, 1420 ; b) nave of the church of Santo Spirito by Brunelleschi, begun 1445; c) the Laurentian Library by Michelangelo, 1525 ff; d) Uffizi arcade by Vasari, 1560 ff. At present the At present the Trassinaia Trassinaia quarry is quarry is abandoned and abandoned and totally degraded. totally degraded. Due to its historical Due to its historical and cultural and cultural importance, it needs importance, it needs large conservation large conservation and restoration and restoration interventions, aimed interventions, aimed to its tourist fruition to its tourist fruition and cultural and cultural recovery recovery TRASSINAIA QUARRY TRASSINAIA TRASSINAIA QUARRY QUARRY MACIGNO OF FIESOLE STRATIGRAPHIC LOG 3D SKETCH VIEW OF THE TRASSINAIA QUARRY A simple computation led to evaluate that this quarry was able to supply all the Pietra Serena stone blocks that were necessary for the Cupola building. 150 m 30 m 12 m Fiesole hills Fiesole GEOLOGICAL MAP OF THE FIESOLE HILLS GEOLOGICAL MAP OF THE FIESOLE HILLS M Firenze Plio Plio- Quaternary Quaternary fluvio fluvio- lacustrine lacustrine deposits deposits Ligurian Ligurian Unit Unit Monte Morello Monte Morello Unit Unit , , Sillano Sillano Frm Frm. Tuscan Tuscan Nappe Nappe San Polo San Polo Marls Marls Macigno Macigno faults faults quarries quarries 1 km Fiesole GEOLOGICAL MAP OF THE FIESOLE HILLS GEOLOGICAL MAP OF THE FIESOLE HILLS M Plio Plio- Quaternary Quaternary fluvio fluvio- lacustrine lacustrine deposits deposits Ligurian Ligurian Unit Unit Monte Morello Monte Morello Unit Unit , , Sillano Sillano Frm Frm. Tuscan Tuscan Nappe Nappe San Polo San Polo Marls Marls Macigno Macigno faults faults quarries quarries 1 km TRASSINAIA QUARRY Cultivated beds 1: sandstones; 2: TBT; 3: siltstones and marls; 4: shales; 5: calcarenites; 6 cultivated layers Main quarries “Contract for Pietra Serena beams for first stone chain of Cupola to be carved in the Trassinaia quarry on the hill of Vincigliata. This order is for 5 delivered pieces a month up to a total of 600. Each is to measure 4 x ¾ x ¾ braccia (2 ¼ br3) x 600 for a total of 1,350 br 3 of hewn stone. The beams are to be cut from the best quality beds: galazone, falda grossa o falda gentile. Not more than 1/6 of the delivery should be of masso. The contractors receive an advance of 50 florins and the loan of quarrying tools”… Floor of the first closing ring (Serraglio) of the Cupola, made of Pietra Serena Stone beams below the second platform visible where the structure is pierced by the stairway
Transcript of THE “PIETRA SERENA” STONES OF BRUNELLESCHI’S CUPOLA · by Brunelleschi, Michelangelo and...
THE “PIETRA SERENA” STONES OF BRUNELLESCHI’S CUPOLAColi Massimo1, Tanini Chiara1, Haines Margharet2, Nenci Cinzia3, Federica Bencini1
1Dept.of Earth Science, University of Florence, Italy – 2Harvard University “Villa i Tatti”, Florence, Italy - 3Dept. of History of Arts, University of Florence, Italy
The Cupola of the Santa Maria del Fiore (Florence Cathedral), was vaulted by Brunelleschi in the years 1420-1436.
From 1417 Brunelleschi participated in the competition for the methods of the realization of the vast Cupola (planned from 1368), and in a document dating 1420 he explained how and with which materials it would be erected.The Cupola was built without any centering from the ground; it was self-sustaining with only a light working scaffolding at the top of the building as the construction proceeded. In order to solve the problem of how to vault the Cupola, Brunelleschi introduced new techniques and a selected and focused use of building materials.
For the supporting masonry Brunelleschirequired Pietraforte, a quartz-carbonate turbidite quarried in the hills south of Firenze.The vaulting-ribs were built in Carraramarble; the bases of the eight vault segments were made of Pietraforte and continued upwards with special sized bricks in a herring-bone pattern.The outward thrusts of the Cupola are contained with chains of a specific type of Pietra Serena, which was quarried at the Trassinaia quarry.
The archives of the Opera del Duomo (www.operaduomo.firenze.it/cupola) show that particular materials were chosen for specific uses, and in many instances the precise quarry where the stones had to come from was specified.
The documentation online, edited with texts and analytic and structured indexes, contains information concerning the selection of quarries, their management by the cathedral work forces, the cutting and transport of stones and the quality controls at construction site. The sources present rich historical terminology for the description of stone types and their appropriateness to various structural applications.
THE CUPOLA
Hypothesis illustrating the disposition of the Pietra Serena stone beams of the first stone chain of the Cupola This stabilizing and binding structure is hidden within the Pietra Forte masonry of the base of the Cupola
It is noteworthy that Pietra Serena was chosen for its tensile strength in this application, while Pietraforte needed only to respond to compression forces. As the Cupola rose, radially disposed bricks took the place of the Pietraforte masonry, but Pietra Serena continued to be employed for working architectural elements such as entablatures and binding elements.
A looking up view to the wood chain, which was installed only on the first level and judged ineffective.
On the basis of its performance in architectonic applications, which depends on the percentages of calcite and grain-package of the single beds, the quarriers were able to recognize different grades of Pietra Serena, the best grade being the Serena Gentile (Gentle Serena) which came from the cultivation of a few specific beds. It was widely used by Brunelleschi, Michelangelo and Vasari for some of the outstanding buildings in Florence.The quarrying activity of the Pietra Serena was established in the Fiesole
hills, north of Firenze, by the Etruscans and last till the middle of the XX Century.
Quarrying activity of Pietra Serena in the hills of Fiesole near Florence goes back to Etruscan times and continues up to the mid-XX century. Pietra Serena is the classical historical name given throughout history by the quarriers to the hewn stones cut away from the best-graded sandstone beds of Macigno in the area around Florence. Macigno is a silicoclastic turbiditic succession derived from the dismantling of the western-central Alps, which in the Oligcene period underwent strong uplift and erosion. Macigno was deposited like an elongated sub-marine fan into the Appennine fore-deep, at the top of the Tuscan sedimentary sequence.Macigno sandstone displays the typical Bouma sedimentary features and all the facies associations described by Mutti & Ricci Lucchi (1972) and Mutti (1992).Macigno was deposited syn-tectonically in middle-late Oligocene, reaching a thickness of about 3 km with a depositional rate of 30 cm/kyand a global volume of about 67.000 km3. Macigno displays different sedimentological characteristics from the bottom to top.
THE PIETRA SERENA
Authors subdivide Macigno vertically into two members: a lower Macigno s.s., typically outcropping in the Chianti region, mainly made of coarse-grained Ta, Ta-c amalgamated beds, and an upper Mt. Modino sandstone constituted by a rhythmic alternation of classic Ta-e beds and thin-bedded turbidite bodies. The Macigno sequence outcropping in the Fiesole hillside north of Florence is related to the topmost layers of the Mt. Modino member. Facies associations recognized in the Macigno in the Fiesole hills point to its formation in an outer-fan depositional environment, with stacked depositional lobes interbedded with interlobe and fringe of thinner beds. The whole sequence seems to be moreproximal, thickening and coarsening upwards, in the uppermost part.The petrographic composition of the Macigno, with reference to the sandstone layers, is almost constant. It is a quartz-feldspatic greywacke with lithicfragments of mainly metamorphic origin; clay is present both as clast and matrix. Calcite is instead present in low percentages (max. 17%) constituting both clasts and cement. The physical and mechanical properties of Macigno coarse sandstone beds are on the average very good and justify uses for structural and ornamental purposes. Despite almost uniform sedimentologicalfeatures, physical-mechanical properties and mineralogical composition, stones from different beds display great differences in operating performance, due to small variations of calcite and clay percentages and of grain size and grain-package.
a b
c d Pietra Serena used as ornamental stone in Florence: a) arcade of the Innocenti hospital by Brunelleschi, 1420 ; b) nave of the church of Santo Spirito by Brunelleschi, begun 1445; c) the Laurentian Library by Michelangelo, 1525 ff; d) Uffizi arcade by Vasari, 1560 ff.
At present the At present the TrassinaiaTrassinaia quarry is quarry is abandoned and abandoned and totally degraded. totally degraded. Due to its historical Due to its historical and cultural and cultural importance, it needs importance, it needs large conservation large conservation and restoration and restoration interventions, aimed interventions, aimed to its tourist fruition to its tourist fruition and cultural and cultural recoveryrecovery
TRASSINAIAQUARRY
TRASSINAIATRASSINAIAQUARRYQUARRY
MACIGNO OF FIESOLE STRATIGRAPHIC LOG
3D SKETCH VIEW OF THE TRASSINAIA QUARRY
A simple computation led to evaluate that this quarry was able to supply all the Pietra Serena stone blocks that were necessary for the Cupola building.
150 m
30 m
12 m
Fiesole hills
Fiesole
GEOLOGICAL MAP OF THE FIESOLE HILLSGEOLOGICAL MAP OF THE FIESOLE HILLS
M
Firenze
PlioPlio--QuaternaryQuaternary fluviofluvio--lacustrinelacustrine depositsdeposits
LigurianLigurian UnitUnitMonte Morello Monte Morello UnitUnit, , SillanoSillano FrmFrm..
TuscanTuscan NappeNappeSan Polo San Polo MarlsMarls
MacignoMacigno
faultsfaults quarriesquarries
1 km
Fiesole
GEOLOGICAL MAP OF THE FIESOLE HILLSGEOLOGICAL MAP OF THE FIESOLE HILLS
M
PlioPlio--QuaternaryQuaternary fluviofluvio--lacustrinelacustrine depositsdeposits
LigurianLigurian UnitUnitMonte Morello Monte Morello UnitUnit, , SillanoSillano FrmFrm..
TuscanTuscan NappeNappeSan Polo San Polo MarlsMarls
MacignoMacigno
faultsfaults quarriesquarries
1 km
TRASSINAIAQUARRY
Cultivated beds
1: sandstones; 2: TBT; 3: siltstones and marls; 4: shales; 5: calcarenites; 6 cultivated layers
Main quarries
“Contract for Pietra Serena beams for first stone chain of Cupola to be carved in the Trassinaia quarry on the hill of Vincigliata. This order is for 5 delivered pieces a month up to a total of 600. Each is to measure 4 x ¾ x ¾braccia (2 ¼ br3) x 600 for a total of 1,350 br3 of hewn stone. The beams are to be cut from the best quality beds: galazone, falda grossa o falda gentile. Not more than 1/6 of the delivery should be of masso. The contractors receive an advance of 50 florins and the loan of quarrying tools”…
Floor of the first closing ring (Serraglio) of the Cupola, made of Pietra Serena
Stone beams below the second platform visible where the structure is pierced by the stairway
