The present work focuses on the main phenomenological features of stone cleaning by lasers. They ... more The present work focuses on the main phenomenological features of stone cleaning by lasers. They are the removal rate, degree of cleaning, and chromatic appearance of the treated surface associated with different conservation problems and laser parameters. A set of three different outdoor stone conservation problems were investigated here. The measurement of the ablation rates were carried out on encrusted
The present work reports a basic investigation aimed at optimizing laser cleaning interventions o... more The present work reports a basic investigation aimed at optimizing laser cleaning interventions on pliocene sandstone of Siena. Irradiation trials were performed with a short free running Nd:YAG laser, on quarry samples and on samples from Palazzo Spannocchi presenting black crust. The physical parameterization associated with a detailed petrographic and mineralogic diagnostics of the induced effects, allowed the irradiation thresholds
Yellowish-brown partly greyish renmants of probable film (superficial and coherent thin layer of ... more Yellowish-brown partly greyish renmants of probable film (superficial and coherent thin layer of substances unrelated to the substratum and without any evident reaction with it) are actually widespread on the surface of the statue. However, because of the obvious severe restrictions on sampling, we have limited our study to only a few, and in places where the withdrawal of the microsample appeared least risky. We carried out mineralogical and petrographic analyses on microfragments of film from seven zones in order to characterise their composition and possibly clarify their nature. Certain patches of beige-yellow films, quite different from the preceding ones, were also sampled and analysed.
Lo studio era inteso ad una caratterizzazione petrografica, in sezione ultrasottile, di alcune “i... more Lo studio era inteso ad una caratterizzazione petrografica, in sezione ultrasottile, di alcune “incrostazioni” di colore giallo-brunastro, di incerta natura, ritrovate sulla superficie marmorea della Pietà Rondanini ed, eventualmente, date alcune somiglianze a livello macroscopico, per tentare un confronto con quelle da noi già studiate sul David di Michelangelo. Dette incrostazioni, che si erano evidenziate una volta rimossa la velatura che estesamente ricopriva l’opera scultorea, interessano principalmente due zone: la prima, più ampia, è ubicata sulla spalla sinistra del Cristo e prosegue verso il basso interessando la mano della Madonna; la seconda, meno estesa, è visibile sulla parte sinistra del costato del Cristo medesimo. Dalla prima zona sono stati prelevati 3 microcampioni, mentre dalla seconda un solo microframmento. Sono stati inoltre prelevati anche due microcampioni dalla gamba sinistra del Cristo. Le analisi condotte sono state di tipo mineralogico-petrografico, osser...
Small cavities of about one millimetre in size are irregularly distributed all over the marble su... more Small cavities of about one millimetre in size are irregularly distributed all over the marble surface of the David. Macroscopic observation excluded the cavities as resulting from deterioration of the material. instead, they can be attributed to the primary structure of the marble quarried from the Apuan Alps. In fact, these kindsof cavities are one of a vast range of defects typical of Apuan marbles. The local quarrymen call them "taròli" and "tarme" in their own dialect depending on their size; less than a millimetre and several millimetres and larger, respectively. The aim of this report is to describe the morphology of these so-called "taròli" and "tarme" in the marble of the David and to demonstrate that they are primary by: a) comparing them with identical structures in several Apuan marble outcrops; b) the mineralogical-petrographic analysis of Apuan marble samples.
The study has been executed in the frame of the façade restoration in order to document the statu... more The study has been executed in the frame of the façade restoration in order to document the status of the surfaces of the stone materials. The objective of a cognitive synthesis via an interdisciplinar study have been achieved by means of petrographic investigations combined with archaeological and historical-architectural studies. In particular, the investigations concerned analyses of samples of bedding mortars, plasters and finishes (coloured or not) related to the plaster or directly applied to the masonry surfaces.
ABSTRACT We investigated the conservation problems of the Porta della Mandorla, a masterpiece of ... more ABSTRACT We investigated the conservation problems of the Porta della Mandorla, a masterpiece of the early Florentine Renaissance. The aim of the work was the statement of practicable cleaning protocols based on laser ablation. To this goal, a thorough petrographic characterisation of the state of conservation was performed, which addressed a set of laser cleaning tests by Q-switching and short free running Nd:YAG lasers. The main optimisation problem was the yellow-orange appearance associated with laser ablation by Q-switching lasers. Following the explanation of such a cleaning result, two practicable solutions based on suitable pulse duration or wavelength selections were successfully demonstrated then different intervention protocols were proposed.
ABSTRACT We investigated the casting cores of twelve large bronze masterpieces of the Florentine ... more ABSTRACT We investigated the casting cores of twelve large bronze masterpieces of the Florentine Renaissance and Mannerism (artworks by Ghiberti, Donatello, Verrocchio, Rustici, and Danti). Materials were characterized in their mineralogical-petrographic features, chemical composition, organic content and fossil traces. The results achieved provide information on the main recipes employed for manufacturing the casting cores, which largely agree with written sources of the time, and shed light on the art foundry processes between the 15th–16th centuries. The data collected point out a pronounced affinity of natural raw materials used in all the casting cores investigated, consisting in silty-sandy clays with a suitable natural fine-grained temper component. A large use of organic fibres and matters of both animal and vegetal origin and a minor use of gypsum in selected workshops (Rustici, Verrocchio) were highlighted. Textural analyses allowed gaining information on direct vs indirect methods of casting, while firing temperatures up to about 1000 °C were estimated from mineralogical and microstructural observations. Despite the strong similarities, significant differences among the various samples analysed were pointed out, providing some initial analytical clues that suggest different practices in separate workshops. Finally, the whole petrographic, geochemical and paleontological data gave information on the provenance of the clayey raw materials. This work represents the first step of a systematic approach to the classification of the core materials used in Florentine foundries along the centuries and shows the significant contribution the petrographic analyses can provide to the interpretation of the execution processes of large bronzes.
The present work focuses on the main phenomenological features of stone cleaning by lasers. They ... more The present work focuses on the main phenomenological features of stone cleaning by lasers. They are the removal rate, degree of cleaning, and chromatic appearance of the treated surface associated with different conservation problems and laser parameters. A set of three different outdoor stone conservation problems were investigated here. The measurement of the ablation rates were carried out on encrusted
The preservation and recovery of monuments are hotly debated topics in the field of cultural heri... more The preservation and recovery of monuments are hotly debated topics in the field of cultural heritage conservation. In the early 1990's, our group in Siena started a study of the stone materials used in the architecture of Siena. The data were then processed by a GIS (Geographic Information System), which allows one to perform a series of interactive data analyses.
In 2004, during archaeological excavations at Populonia, a mosaic pavement decorated by perspecti... more In 2004, during archaeological excavations at Populonia, a mosaic pavement decorated by perspective cubes emblema in opus sectile, dated at the end of II century b.c., was discovered. The aim of this work is to examine the working technique and the petrographical analysis of constituent materials and support layers. The analysis carried out by polarized light microscopy allowed for the identification of marly and silicified limestones and white marble, likely to be of local provenance. The use of marble is significant because, according to archaeological literature, it would have been absent in these first examples of sectilia, made completely of poor materials as coloured limestones lime schists, marls, etc. The use of marble could be explained by its ready availability in the near Campiglia area where the existence a quarry (Campo alle Buche), already exploited in Ellenistic period, is documented. KEY-WORDS: Populonia, mosaic pavement, opus sectile, marble, limestone.
The present work focuses on the main phenomenological features of stone cleaning by lasers. They ... more The present work focuses on the main phenomenological features of stone cleaning by lasers. They are the removal rate, degree of cleaning, and chromatic appearance of the treated surface associated with different conservation problems and laser parameters. A set of three different outdoor stone conservation problems were investigated here. The measurement of the ablation rates were carried out on encrusted
The present work reports a basic investigation aimed at optimizing laser cleaning interventions o... more The present work reports a basic investigation aimed at optimizing laser cleaning interventions on pliocene sandstone of Siena. Irradiation trials were performed with a short free running Nd:YAG laser, on quarry samples and on samples from Palazzo Spannocchi presenting black crust. The physical parameterization associated with a detailed petrographic and mineralogic diagnostics of the induced effects, allowed the irradiation thresholds
Yellowish-brown partly greyish renmants of probable film (superficial and coherent thin layer of ... more Yellowish-brown partly greyish renmants of probable film (superficial and coherent thin layer of substances unrelated to the substratum and without any evident reaction with it) are actually widespread on the surface of the statue. However, because of the obvious severe restrictions on sampling, we have limited our study to only a few, and in places where the withdrawal of the microsample appeared least risky. We carried out mineralogical and petrographic analyses on microfragments of film from seven zones in order to characterise their composition and possibly clarify their nature. Certain patches of beige-yellow films, quite different from the preceding ones, were also sampled and analysed.
Lo studio era inteso ad una caratterizzazione petrografica, in sezione ultrasottile, di alcune “i... more Lo studio era inteso ad una caratterizzazione petrografica, in sezione ultrasottile, di alcune “incrostazioni” di colore giallo-brunastro, di incerta natura, ritrovate sulla superficie marmorea della Pietà Rondanini ed, eventualmente, date alcune somiglianze a livello macroscopico, per tentare un confronto con quelle da noi già studiate sul David di Michelangelo. Dette incrostazioni, che si erano evidenziate una volta rimossa la velatura che estesamente ricopriva l’opera scultorea, interessano principalmente due zone: la prima, più ampia, è ubicata sulla spalla sinistra del Cristo e prosegue verso il basso interessando la mano della Madonna; la seconda, meno estesa, è visibile sulla parte sinistra del costato del Cristo medesimo. Dalla prima zona sono stati prelevati 3 microcampioni, mentre dalla seconda un solo microframmento. Sono stati inoltre prelevati anche due microcampioni dalla gamba sinistra del Cristo. Le analisi condotte sono state di tipo mineralogico-petrografico, osser...
Small cavities of about one millimetre in size are irregularly distributed all over the marble su... more Small cavities of about one millimetre in size are irregularly distributed all over the marble surface of the David. Macroscopic observation excluded the cavities as resulting from deterioration of the material. instead, they can be attributed to the primary structure of the marble quarried from the Apuan Alps. In fact, these kindsof cavities are one of a vast range of defects typical of Apuan marbles. The local quarrymen call them "taròli" and "tarme" in their own dialect depending on their size; less than a millimetre and several millimetres and larger, respectively. The aim of this report is to describe the morphology of these so-called "taròli" and "tarme" in the marble of the David and to demonstrate that they are primary by: a) comparing them with identical structures in several Apuan marble outcrops; b) the mineralogical-petrographic analysis of Apuan marble samples.
The study has been executed in the frame of the façade restoration in order to document the statu... more The study has been executed in the frame of the façade restoration in order to document the status of the surfaces of the stone materials. The objective of a cognitive synthesis via an interdisciplinar study have been achieved by means of petrographic investigations combined with archaeological and historical-architectural studies. In particular, the investigations concerned analyses of samples of bedding mortars, plasters and finishes (coloured or not) related to the plaster or directly applied to the masonry surfaces.
ABSTRACT We investigated the conservation problems of the Porta della Mandorla, a masterpiece of ... more ABSTRACT We investigated the conservation problems of the Porta della Mandorla, a masterpiece of the early Florentine Renaissance. The aim of the work was the statement of practicable cleaning protocols based on laser ablation. To this goal, a thorough petrographic characterisation of the state of conservation was performed, which addressed a set of laser cleaning tests by Q-switching and short free running Nd:YAG lasers. The main optimisation problem was the yellow-orange appearance associated with laser ablation by Q-switching lasers. Following the explanation of such a cleaning result, two practicable solutions based on suitable pulse duration or wavelength selections were successfully demonstrated then different intervention protocols were proposed.
ABSTRACT We investigated the casting cores of twelve large bronze masterpieces of the Florentine ... more ABSTRACT We investigated the casting cores of twelve large bronze masterpieces of the Florentine Renaissance and Mannerism (artworks by Ghiberti, Donatello, Verrocchio, Rustici, and Danti). Materials were characterized in their mineralogical-petrographic features, chemical composition, organic content and fossil traces. The results achieved provide information on the main recipes employed for manufacturing the casting cores, which largely agree with written sources of the time, and shed light on the art foundry processes between the 15th–16th centuries. The data collected point out a pronounced affinity of natural raw materials used in all the casting cores investigated, consisting in silty-sandy clays with a suitable natural fine-grained temper component. A large use of organic fibres and matters of both animal and vegetal origin and a minor use of gypsum in selected workshops (Rustici, Verrocchio) were highlighted. Textural analyses allowed gaining information on direct vs indirect methods of casting, while firing temperatures up to about 1000 °C were estimated from mineralogical and microstructural observations. Despite the strong similarities, significant differences among the various samples analysed were pointed out, providing some initial analytical clues that suggest different practices in separate workshops. Finally, the whole petrographic, geochemical and paleontological data gave information on the provenance of the clayey raw materials. This work represents the first step of a systematic approach to the classification of the core materials used in Florentine foundries along the centuries and shows the significant contribution the petrographic analyses can provide to the interpretation of the execution processes of large bronzes.
The present work focuses on the main phenomenological features of stone cleaning by lasers. They ... more The present work focuses on the main phenomenological features of stone cleaning by lasers. They are the removal rate, degree of cleaning, and chromatic appearance of the treated surface associated with different conservation problems and laser parameters. A set of three different outdoor stone conservation problems were investigated here. The measurement of the ablation rates were carried out on encrusted
The preservation and recovery of monuments are hotly debated topics in the field of cultural heri... more The preservation and recovery of monuments are hotly debated topics in the field of cultural heritage conservation. In the early 1990's, our group in Siena started a study of the stone materials used in the architecture of Siena. The data were then processed by a GIS (Geographic Information System), which allows one to perform a series of interactive data analyses.
In 2004, during archaeological excavations at Populonia, a mosaic pavement decorated by perspecti... more In 2004, during archaeological excavations at Populonia, a mosaic pavement decorated by perspective cubes emblema in opus sectile, dated at the end of II century b.c., was discovered. The aim of this work is to examine the working technique and the petrographical analysis of constituent materials and support layers. The analysis carried out by polarized light microscopy allowed for the identification of marly and silicified limestones and white marble, likely to be of local provenance. The use of marble is significant because, according to archaeological literature, it would have been absent in these first examples of sectilia, made completely of poor materials as coloured limestones lime schists, marls, etc. The use of marble could be explained by its ready availability in the near Campiglia area where the existence a quarry (Campo alle Buche), already exploited in Ellenistic period, is documented. KEY-WORDS: Populonia, mosaic pavement, opus sectile, marble, limestone.
Digital imaging allows to collect and process morphometric quantitative data on archaeological fi... more Digital imaging allows to collect and process morphometric quantitative data on archaeological finds. The Research Unit of Prehistory and Anthropology of the University of Siena is currently developing new protocols for the analysis of bone modifications using a Hirox Digital Microscope KH-7700. This instrument captures 3D images of the observed surfaces enabling the direct observation of butchering marks, artistic engravings and non-anthropic evidences (for instance tooth marks) from several points of view; it also allows a rapid procurement of several quantitative data (linear and angular measurements) that can be processed through univariate and multivariate statistics. After the analysis of more than four hundred specimens, we are presenting in this paper the results of several case-studies from Italian Palaeolithic and Metal Age sites: we demonstrated that processing quantitative data it is possible to separate between butchering marks inflicted using stone and metal tools; to identify the kind of stone tool used to produce prehistoric artistic engravings; to separate between butchering marks and artistic engravings. All data coming from the analysis of archaeological specimens are compared with those obtained carrying out experimental proofs; it allows to corroborate our results. The encouraging obtained outcome confirms the validity of our protocols and the important role that computer applications and quantitative methods play for understanding prehistory.
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Papers by Marco Giamello