La scenografia degli stucchi del Serpotta rivisitata. La materia e la forma
10.6092/issn.1973-9494/6182
La materia che si nasconde sotto le levigate e lucenti superfici degli stucchi della famiglia dei Serpotta, che operò in Sicilia tra il 1670 e il 1730, è stata ampiamente studiata in precedenti lavori, rivelando la profonda, se pur empirica, conoscenza della Scienza dei Materiali che guidava gli artisti nella realizzazione dei loro capolavori. In questo studio l’attenzione viene posta sulla prospettiva solida e sulla scultura scenografica dello scultore palermitano Giacomo Serpotta, riconosciuto come il principale esponente della Scuola. L’indagine si concentra su particolari opere dell’artista, i cosiddetti “teatrini plastici”, da lui eseguiti per l’Oratorio di San Lorenzo nel centro antico di Palermo. Sulla base di documenti di archivio e rilevamenti stereo fotogrammetrici analogici pregressi, integrati con tecniche di acquisizione dati di ultima generazione, lo studio presenta elaborazioni digitali che hanno permesso ricostruzioni virtuali a video di elementi scultorei non più esistenti. La conoscenza dei materiali che compongono le opere in stucco, insieme alla capacità di riprodurre con precisione le forme, offre interessanti possibilità di fornire una lettura completa delle opere d’arte danneggiate dal deterioramento o dal furto.
application/pdf
1973-9494
6182
en
Giovanni Rizzo
Conservation Science in Cultural Heritage
virtual reassembly
The Scenography of Serpotta Stuccoes Revisited - Material and Form
Text.Serial.Journal
https://conservation-science.unibo.it/
15
Articles
2015-12-30
2016-06-08
2015-12-30
2017-09-04
281-313
CSCH
Giovanni Rizzo
2015/12/30
10.6092/issn.1973-9494/6182
281
Università di Palermo
1973-9494
virtual reassembly
en
313
SUMA, D., SAVINO, N., GALASSO, O., Services in support of promoting territorial tourism and culture: the living lab project EPULIA, in “Conservation Science in Cultural Heritage”, Issue n. 14, pp. 263-268, ISSN 1973-9494.
The Scenography of Serpotta Stuccoes Revisited - Material and Form
https://conservation-science.unibo.it/article/download/6182/5957
15
T    HE SCENOGRAPHY OF SERPOTTA STUCCOES
     REVISITED - MATERIAL AND FORM


   Salvatore Barba
   Dipartimento di Ingegneria Civile
   Università del Salento, Italy

   Francesco Di Paola*
   Dipartimento di Architettura
   Università di Palermo, Italy
   Istituto EuroMediterraneo di Scienza e Tecnologia
   Dipartimento di Communicazione, Grafica Interattiva e Realtà Aumentata
   Palermo, Italy

   Giovanni Rizzo
   Dipartimento di Ingegneria Civile, Ambientale , Aerospaziale e dei Materiali
   Università di Palermo, Italy


   Keywords: philological reconstruction, 3D scanning technique, geometric pro-
   cessing, virtual reassembly


   1. Introduction




                                                                                                       CONSERVATION SCIENCE IN CULTURAL HERITAGE
    In order to develop an effective scientific investigation process ������������������������
                                                                      in����������������������
                                                                         the field of diagnos-
tics, conservation, protection and valorisation applied to Cultural Heritage, it is essential
to promote the formation of interdisciplinary groups with different professional compe-
tences and test, define and propose specific methodologies and operative protocols.
    In the specific field of architectural survey and restoration, particular techniques and
the use of non-invasive equipment are becoming increasingly more common. Numerous
scientific and technological advances have been achieved through projects financed by
research authorities, universities, companies and firms specialised in the sector [1].
    Focusing on our experience, the acquisition, processing and understanding of het-
erogeneous data extrapolated from the application of specific interdisciplinary instru-
mental methods, has determined a crucial point in the methodological approach aimed
at proposing an operative protocol in the specific field of protection, conservation and
valorisation of cultural heritage [2].
    In this paper we report the in-depth analysis conducted on the “small-scaled plastic
theatres” of the San Lorenzo Oratory in Palermo, which are emblematic evidence of
Serpotta’s stucco workmanship and admirably combine geometry, art and architecture.1
    The architectural-compositional complexity of the object of the research and the inter-
esting scenographic-spatial expedients utilised to create the micro-architectures of these
incredible truncated pyramidal “boxes”, constituted the basis for this study (Figure 1).

* Corresponding author: francesco.dipaola@unipa.it

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G. Chidichimo, F. Dalena, A. Beneduci - The scenography of Serpotta stuccoes




                                                                                 Figure 1. Methodological approach and proposal for an operative protocol in the specific field of
                                                                                 Cultural Heritage protection, conservation and valorisation. The “small-scaled plastic theatres” of
                                                                                 the sculptor Giacomo Serpotta.

                                                                                    For more than 70 years, the Serpotta family represented the best of stucco art in Sicily
                                                                                 between the 17th and 18th centuries. Although the progenitor was Gaspare Serpotta, his son
                                                                                 Giacomo is recognized as the most refined and famous artist of the family. The activity of the
                                                                                 school continued with Giacomo’s son, Procopio, and then with his son, Giovanni. However,
                                                                                 Giacomo’s expressive refinement would remain unequaled.
                                                                                    Following the devastating and destructive events of the Second World War, many
                                                                                 churches and oratories decorated with Serpotta stuccoes were heavily damaged; some
                                                                                 restoration work was done, but they then fell into oblivion for decades. As a result, some

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of the decorative elements fell into a state of deterioration that reached a point of almost
no return.
    Fortunately, at the end of the 20th century, the entire cycle of stuccoes received due at-
tention; firstly, thanks to the impassioned interest of Donald Garstang and secondly, to the
so called “Serpotta Project”, initiated in 1999 by the Soprintendenza BB. CC. (Monuments
and Fine Arts Office) of Palermo which, in its first stages, dealt with the restoration of the
decorative elements of ten monumental buildings [3].
    The “Serpotta Project” represented a unique opportunity for systematically sampling the
stuccoes and carrying out a comparative analysis of the results obtained from the physical
chemical investigation, thus highlighting new elements in this extraordinary artistic heritage
that until now had been studied above all from a historical and artistic point of view.
    For some of the more seriously damaged works, a number of them with missing parts,
it was possible to acquire first-hand knowledge. This was done by visually observing and
photo-documenting the mass stratigraphy of the stucco, thus identifying the sequence of
steps followed by the Serpottas in realising their sculptures and recognizing the materials
used for reinforcement, such as wood, iron, or reed, chosen according to the features of the
figurative work of art.
    This enabled the stratigraphic succession of the Serpottas’ work in its entirety to be stud-
ied in depth, starting from the materials used for the framework and gradually going through
the different layers of stucco used for the allegorical figures. These included angels and putti
as well as the frames and refined decorative elements which were all first roughly drafted,
then beautifully finished.
    Identification of the wood species used for the supporting ribs was carried out and the
stuccoes underwent mineralogical and petrographic analyses.
    The obtained results contributed to defining a “material” interpretation of the Serpotta
work, by providing insight into cases of uncertain attribution and crediting the artists with an
undeniable though empirical, deep knowledge of the materials used. Characterization of the
constitutive materials, moreover, provided the basis of the knowledge, essential in defining




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the right intervention of restoration.
    Unfortunately however, conservation work cannot completely restore the original read-
ing to those parts of the decorative features that have been stolen. The thieves’ attention
focused on those elements which could easily be sold on the black market. For this reason,
the missing elements that were removed were, for the most part, heads of putti, the musical
instruments of the angel musicians and the figurines of the “small-scaled plastic theatres”,
as in the case of the San Lorenzo Oratory (Figure 2).




Figure 2. San Lorenzo Oratory, Palermo. Side and background walls from the altar.

                                                                                                   283
                                                                                    2. Material composition of the stuccoes: stratigraphic succession

                                                                                     What is generically called stucco, when referring to the Serpotta works of art is, in
                                                                                 reality, a material with a variable composition and is not at all random. It is astonishing
                                                                                 to observe the ability of the Serpottas in adapting the characteristics of their mixtures
                                                                                 to the different phases of their work.
                                                                                     For large works they used a wooden structure around which a first volume was
                                                                                 drafted, we will call it Layer C. Its main quality was that it had to harden quickly to pre-
                                                                                 vent it from sliding downwards under the effect of gravity.
                                                                                     For this reason, Layer C consisted mainly of gypsum, identified both in the binder
                                                                                 matrix and in the aggregates and secondarily of calcite and other minor minerals that
                                                                                 are occasionally present.
                                                                                     The shape of the work was then modeled by overlaying a less consistent second
                                                                                 layer, Layer B, measuring from a few millimeters to several centimeters in thickness, of
                                                                                 a mixture that had to give the artist time to refine all the parts of the figure and for this
                                                                                 reason both lime and gypsum were used as binders.
                                                                                     The mineralogical petrographic analysis of Layer B evidences calcite as the main
G. Chidichimo, F. Dalena, A. Beneduci - The scenography of Serpotta stuccoes




                                                                                 phase, associated with quartz and, at times, with a variety of other secondary miner-
                                                                                 alogical phases.
                                                                                     Finally, a white mortar a few millimeters thick was applied, Layer A, a finishing stra-
                                                                                 tum that constituted a sort of “skin” to which the figurative expressiveness was entrust-
                                                                                 ed. It is made of a magnesium-rich lime as binder, with marble powder as aggregate,
                                                                                 so that after hardening, it consisted of calcite, as a main phase and magnesite.
                                                                                     Some examples of the stratigraphic succession are shown in Figure 3.




                                                                                                              A                                 B

                                                                                 Figure 3. The wooden reinforcement and the succession of different layers of stucco in damaged
                                                                                 statues from the S. Mercurio Oratory (A) and the Stigmata Monastery (B). Technical file for
                                                                                 electronic storage of the results of the mineralogical petrographic analysis.

                                                                                    During the “Serpotta Project” more than 150 thin or polished cross sections were pre-
                                                                                 pared, observed and analyzed. Furthermore, the following physical chemical analyses


                                                                           284
were performed: optical microscopy in both reflected and transmitted light, X Ray dif-
fractometry, simultaneous thermal analysis, ionic chromatography, gas chromatography.
   The results are collected in the form of tables and technical files, as shown in Figure
3. An evident evolution in Giacomo Serpotta’s artistic production can be observed both
in his artistic expression and his choice of materials.
   In later works of art, such as in the San Lorenzo Oratory (1699-1707), there is just
one layer of body adherent to the wooden structure, whereas the finishing Layer A,
again made using a magnesium-rich lime as binder, is slightly different in both the
amount and the particle size distribution of the marble dust, as reported in Figure 4.
   Due to the small size of the figures in the so called “small-scaled plastic theatres”,
the frame is made of a thin iron rod, wrapped in hemp fibers or strings.
   The same iron reinforcement is used for the thin parts of the statues, such as the fingers,
and for some protruding decorative elements, such as the acanthus leaves (see Figure 4).
   This coating, used also for the wooden frames, as already shown in Figure 3, is
extremely effective in making the stucco work more durable, as the hemp not only
prevents direct contact of the iron or wood with the plaster, but also acts as a soft joint
which is effective in compensating the differential expansion of the different materials
caused by changes in temperature and humidity.
   This is only one example of the technical skill of the Serpotta School, definitely sur-
prising when compared to their opportunities for technical education and training [4-5-6].




                                                                                                        CONSERVATION SCIENCE IN CULTURAL HERITAGE




Figure 4. Iron rod, wrapped in hemp, as reinforcement of a missing figure in a “small-scaled
plastic theatre” of the San Lorenzo Oratory (A) and of the finger of a statue from the Stigmata
Monastery.


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                                                                                    3. Stucco form: case study of the little Serpotta theatre “St. Francis in the act
                                                                                    of clothing a poor man”

                                                                                     In 1600, in Palermo, religious orders and “Companies” used to build small outbuild-
                                                                                 ings adjoining their churches as places of worship where they could perform spiritual
                                                                                 exercises, sermons and other religious activities.
                                                                                     These small rooms, known as “oratories”, were initially conceived with very simple
                                                                                 ornamental apparatus and composed of one single-aisle chamber illuminated by big
                                                                                 rectangular windows, without chapels and with an arch between the chamber and the
                                                                                 chancel, this last being generally square and covered by a small dome.
                                                                                     The baroque style and the competitiveness among Palermo “Companies” in adorn-
                                                                                 ing their oratories contributed to transforming and reviving these places through rich
                                                                                 and luxurious decorations which conformed to the standards of that time.
                                                                                     The simple architectural framework of the pilaster strips, the window frames, the
                                                                                 ledges, the bases, are wonderfully embellished and enlivened by complex decora-
                                                                                 tive compositions constituted by plasters representing allegorical statues, little angels,
                                                                                 garlands, festoons [7].
G. Chidichimo, F. Dalena, A. Beneduci - The scenography of Serpotta stuccoes




                                                                                     The figure of Giacomo Serpotta fitted well into this lively cultural atmosphere. The
                                                                                 sculptor, with his brilliant flair and ability in the art of stucco, modelled and moulded
                                                                                 sculptures that are quite unique.
                                                                                     Among the many city oratories, the San Lorenzo Oratory is certainly one of the most
                                                                                 interesting, due to the coexistence of extraordinary works of art. The oratory was built
                                                                                 by the “Compagnia” of St. Francis of Bardigli and Cordiglieri on the site of a church
                                                                                 dedicated to St. Lawrence, given to the brothers in 1569.2
                                                                                     The compositional cycle covers the chamber walls completely, alternating allegori-
                                                                                 cal female figures of the Virtues with small original perspective plastic theatres, and
                                                                                 tells the story of the life of St. Lawrence (on the right wall from the entrance) and of St.
                                                                                 Francis (on the left wall from the entrance). The vast repertoire of images and depic-
                                                                                 tions on the walls must certainly have inspired awe and wonder in the visitor [8].
                                                                                     Our interest focuses on the sculptor’s meticulous realisation of the eight perspective
                                                                                 scenes in the little magical boxes which reveal his deep knowledge of the geometrical
                                                                                 laws governing vision and the perception of perspective.
                                                                                     These frames, placed at a height of almost 4.50 metres from the floor, contain some
                                                                                 low relief hagiographic scenes of the two saints with figures in the round animating
                                                                                 the “small-scaled plastic theatres”, and appearing out of proportion compared with the
                                                                                 large-sized allegorical figures arranged around the edges.
                                                                                     As repeatedly highlighted by scholars [9-10-11], Serpotta succeeds in moulding an
                                                                                 innovative and spontaneous scenographic space, relating natural and architectural
                                                                                 elements with human figures in the round, which do not always respect perspective
                                                                                 accuracy (undoubtedly differing in this aspect from illustrious predecessors like Gagini
                                                                                 and Brunelleschi).
                                                                                     In this study, we report on our experience relating to one of the eight little Serpotta
                                                                                 theatres, focusing in particular on the scene of “St. Francis in the act of clothing a poor
                                                                                 man” (Figure 5).
                                                                                     The process of knowledge acquisition through the integration of different survey
                                                                                 methods was performed on the sampled little theatre as an experimental test in order
                                                                                 to structure an operative protocol to be extended to the study of all the oratory theatres.



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Figure 5. San Lorenzo Oratory, Palermo. “St. Francis in the act of clothing a poor man”. Giacomo
Serpotta. Picture taken before the theft of the St. Francis statue, placed at the bottom right corner.
A recent picture after restoration work, evidencing the theft of the St. Francis statue.



   4. Integrated survey techniques

    The partial results obtained constitute the continuation of a survey performed in the
80s by a team from the former Design Institute of the University of Palermo, with tradi-
tional analog stereophotogrammetric shooting and restitution techniques. The recent
data acquisition and processing conducted by means of non-invasive techniques of
image-based technologies (photogrammetry and photomodeling) and reverse engi-
neering (3D scanning) took place without direct contact with the object, through the
mediation of optical, mechanical and ICT tools, providing a representation of the object
in the form of a three-dimensional model [12-13].3
    The use of the tools employed in these three-dimensional metric measurement




                                                                                                               CONSERVATION SCIENCE IN CULTURAL HERITAGE
techniques, proved to be suitable for the geometrical characteristics of the object un-
der examination, offering remarkable productivity and high precision standards com-
pared to equipment of the past [14].
    By using minimal non-invasive interventions, the survey was able to maintain the
integrity and authenticity of the historical-artistic heritage, highlighting the undeniable
benefits of the digital process in terms of reliability and management, in addition to
creating a data bank which is consultable and implementable in view of its future con-
servation and transmission.

   4.1 The photogrammetric survey of the 80s and photo-modeling process

   As stated in the previous paragraph, in the preliminary phase we availed ourselves
of a previous stereophotogrammetric survey conducted in the 1980s by a team from
the former Design Institute of the University of Palermo. The shots were taken using
a Wild C40 with a shooting base of 400 mm and a 1:5 scale restitution of the stereo-
scopic model, according to the grapho-numerical representation method with contour
lines, through a Wild A40 analog restitutor (Figure 6) [15].
   The non-invasive technique, which at that time was efficient and state-of-the-art, al-
lowed only two of the little plastic theatres of the San Lorenzo Oratory to be inspected,
due to the overheads of the whole process and the difficulty in accessing the premises.


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G. Chidichimo, F. Dalena, A. Beneduci - The scenography of Serpotta stuccoes




                                                                                 Figure 6. San Lorenzo Oratory, Palermo; “St. Francis in the act of clothing a poor man”. Giacomo
                                                                                 Serpotta. Photogrammetric restitution with contour lines. Original scale 1:5 (D’Alessandro,
                                                                                 Pizzurro, 1989).

                                                                                     The restoration work of 2003, facilitated access to the oratory and made moving
                                                                                 around in the spaces of the chamber during the acquisition phase much easier. This
                                                                                 has allowed us to extend the practical photographic shooting to the whole ornamental
                                                                                 decoration of the oratory and to collect a considerable amount of data (geometry and
                                                                                 texture), encoded into high resolution images, and which will be useful for the graphic
                                                                                 restitution of the 3D models, their analysis and digital use.
                                                                                     In the initial study phase, we decided to elaborate a first three-dimensional refer-
                                                                                 ence model with the assistance of photo-modelling, an innovative rapid digital technol-
                                                                                 ogy which allows the creation of a three-dimensional point cloud. The processed data
                                                                                 were integrated and implemented in the second acquisition phase with a 3D scanning
                                                                                 technique.
                                                                                     Once the shooting project was designed, the photographic data were acquired with
                                                                                 a Nikon D3200 digital camera with a CMOS 24.2 megapixel image sensor and with a 6
                                                                                 megapixel minimum resolution and wide-angle lens. A rolling scaffold was used for the
                                                                                 photogrammetric survey which enabled us to reach a height of 4.30 m, thus ensuring
                                                                                 the correct shooting of the frames.
                                                                                     The open source software used for the restitution of the three-dimensional scenes is
                                                                                 the popular Autodesk 123D Catch web service based on “image-based 3D modeling”
                                                                                 algorithms for the reconstruction of three-dimensional scenes and the reproduction of
                                                                                 digital models which are structured on the basis of the initial raster images.
                                                                                     Without going into the details of the procedural logic linked to technologies known
                                                                                 in literature as Structure from Motion pipeline, the software automatically performs a
                                                                                 correspondence among images, determines the camera calibration and finds the cor-
                                                                                 respondences among the elements known from the projective geometry of the different
                                                                                 representations [16-17-18].
                                                                                     Since the sculptural object of the research has a concave geometric shape, limited


                                                                           288
metric dimensions and uniformity in the colour rendering, we expected results with
formal imperfections and shadow cones which were partially corrected during the fin-
ishing operations and optimised by aligning complementary clouds.
    The resulting 3D polygonal mesh, though suitable for an overall virtual visualisation
of the sculptural apparatus, does not present a high level of accuracy and reliability
with regard to the graphic representation scale of 1:1 and does not assure correctness
of the measurement for the subsequent geometrical analyses (Figure 7).
    Therefore, in a second learning phase, recourse to the 3D scanning technique was
considered necessary to realise a highly informative model, as required by the survey
project objectives.




                                                                                                           CONSERVATION SCIENCE IN CULTURAL HERITAGE
Figure 7. Screenshot of the well-known Autodesk web service 123D Catch software based on
“image-based 3D modeling” algorithms. Perspective visualisation of the model of the little theatre
of “St. Francis in the act of clothing a poor man”, structured dataset of 26 images.



   4.2 The 3D scanning technique

    Among the new technologies currently proposed for application to cultural heritage,
the use of 3D scanners represents a significant example of how originally very different
fields, such as conservation, research and that of the advanced technologies industry,
can find common ground, such as in the non-invasive experimental use of method-
ologies and innovative tools for analysis procedures of geometric-dimensional data,
restoration and structural monitoring.
    Deferring an in depth-analysis of the technique to a later date, we highlight that a va-
riety of 3D scanners are available on the market, each with different characteristics in
the principle of acquisition, achievable precision, and range and speed of acquisition.
    For the survey project conducted in the oratory, we chose to use the 3D portable
scanning system with an Artec MH structured light flash bulb (instrument supplied by
the Models Laboratory of the Department of Civil Engineering - DICIV, of the University
of Salerno).


                                                                                                     289
                                                                                     Artec MH is a 3D scanner with a fairly simple scanning procedure, as it is sufficient
                                                                                 to move around the object continuously and film it from various angles.4
                                                                                     The extremely versatile system (it does not need markers), functional, rapid and ca-
                                                                                 pable of acquiring almost 500,000 points per second, proved to be particularly suited to
                                                                                 the geometric-dimensional features of the object (indeed the acronym “MH” indicates
                                                                                 a “Medium” field of application, perfectly in line with the dimensions of the small-scaled
                                                                                 plastic theatres) and the goals to reach in terms of metric precision.
                                                                                     By geo-referencing the acquired frames, the related proprietary software automati-
                                                                                 cally joins them all in a single mesh (Figure 8).5
                                                                                     In this specific case, due to the particular shape of the object, immediately deter-
                                                                                 mining global alignment in one single swipe would have been difficult. Consequently,
                                                                                 it was decided to implement a project involving a series of smaller acquisitions, of the
                                                                                 order of a few tens of seconds, as shown in Figure 8.
                                                                                     Unlike the subsequent MHT model, the instrument used does not allow images to
                                                                                 be captured, so the texturing took place during the post-processing.
                                                                                     Procedures for alignment, recording and texturing were carried out using the Geo-
                                                                                 magic Studio software. It is a reverse engineering programme that manages data from
G. Chidichimo, F. Dalena, A. Beneduci - The scenography of Serpotta stuccoes




                                                                                 scans or photogrammetric 3D takes, deals with point clouds, generates mesh models,
                                                                                 designs and exports CAD surfaces and automatically creates NURBS sections and/or
                                                                                 surfaces for modelling.
                                                                                     In the little theatre model, exported in .ply format within the CAD modelling software
                                                                                 NURBS Rhinoceros, the digital statue of St. Francis was placed in its original position
                                                                                 (the modeling process of the statue is described later in paragraph 5).
                                                                                     The highly dense mesh (more than 7.7 million polygons) allows an integral reading
                                                                                 of the perspective scene and an analysis of the scenographic sculptural composition
                                                                                 as Serpotta conceived it.


                                                                                    5. The graphic-geometrical analysis

                                                                                     The plastic construction of the low-reliefs and the scenographic studies of Serpot-
                                                                                 ta’s volumetric compositions follow the geometric laws of solid homology. Homogra-
                                                                                 phy is the process of transforming a parallelepiped prismatic space into a truncated
                                                                                 pyramidal one by means of geometric processes of contraction. The practical purpose
                                                                                 of this kind of perspective is to give the illusion of greater apparent depth to a given
                                                                                 architectural environment [19].
                                                                                     By representing perspective in a vertical framework, the true shape and size of the
                                                                                 walls and floor in a scene are realized in such a way as to perceive a depth greater
                                                                                 than that which actually exists. By tilting the framework corresponding to the prosceni-
                                                                                 um, the vertical and horizontal sections belonging to the planes that are perpendicular
                                                                                 to the framework were obtained.
                                                                                     When the observer’s viewing point overlaps with the centre of the homology, “(V)”
                                                                                 in Figure 10, the prepared scenographic construction leads the spectator to perceive
                                                                                 an illusory space which is different from the real one, with the effect of extending it
                                                                                 (Figure 9).
                                                                                     As regards the sculptural setting of the scene, as repeatedly asserted by scholars,
                                                                                 Serpotta does not rigidly respect the laws of scenographic solid perspective, adopting
                                                                                 some expedients related, more often than not, to his brilliant flair. For example, the


                                                                           290
figures and the architectural and naturalistic elements become gradually smaller while
moving back towards the background and the straight classical architectural elements
do not all vanish at one single point.




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Figure 8. “St. Francis in the act of clothing a poor man”. View in perspective of the polygon
mesh model processed from data acquisition with 3D scanning technique. Interface of the post-
processing software, Geomagic Studio.



   6. The organic modeling process of the statue of St. Francis

    One of the predetermined goals is to fully reconfigure the perception of perspective
in the little theatres by reproducing the missing sculptures virtually.


                                                                                                291
G. Chidichimo, F. Dalena, A. Beneduci - The scenography of Serpotta stuccoes




                                                                                 Figure 9. Study of the real shape and size of the floor and walls in a scene of the “small-scaled
                                                                                 plastic theatres”, in the scenographic sculpture of Giacomo Serpotta.

                                                                                     Here we present the first results of the virtual restoration performed on one sample
                                                                                 of the small scenes, “St. Francis in the act of clothing a poor man”, in which the statue
                                                                                 of the saint is currently absent. As already underlined in the previous paragraphs,
                                                                                 the scientific methodological process of reproducing the sculpture was made possible
                                                                                 thanks to the finding of graphic-numerical restitutions processed during a previous
                                                                                 stereo-photogrammetric survey conducted before the theft of the statue.
                                                                                     The 1:5 scale tables produced in the 80s represented by means of contour lines,
                                                                                 and the historical photographs found by one of the few photographers allowed to enter
                                                                                 the oratory, show the complexity of the organic form of the statue.
                                                                                     Unfortunately, the indirect sources and the scaled drawings report the volumetric-
                                                                                 spatial information of the statue in the round, but are not exhaustive, as they only show
                                                                                 the visible part and its outline. However, it is the only reliable scientific evidence of the
                                                                                 complete scenographic apparatus (Figure 10).
                                                                                     In the field of Computer Graphics, the interactive digital sculpture techniques of
                                                                                 numerical models represent the state of the art software in the field of the organic
                                                                                 modelling of complex freeform surfaces.
                                                                                     Implementation of the tools allows the user to interactively paint or sculpt 3D mod-
                                                                                 els, enriching their geometric and surface details, demonstrating potential in terms of
                                                                                 quality, precision and speed in preparing graphic documents, and versatility in terms of
                                                                                 managing and controlling space.
                                                                                     The panorama is so rich and varied as to often generate difficulties in choosing
                                                                                 more specific software according to personal needs, and due to the fact it requires a
                                                                                 high level of applied knowledge.6



                                                                           292
                                                                                                          CONSERVATION SCIENCE IN CULTURAL HERITAGE
Figure 10. Synoptic table of the organic modelling process for the St. Francis statue, based on a
previous stereo-photogrammetric survey from the end of the 80s.



   7. Conclusions and future in-depth analyses

   The investigative survey, divided into different in-depth study phases, aims to test
an operative protocol which will allow some important aspects of the admirable exam-
ples analysed to be read, interpreted and validated.
   The study examines the state of conservation of the material, the geometric-spatial
shape and the constructive genesis of the scenographic structure of the “small-scaled
plastic theatres”, highlighting the particular way the sculptor constructed the spaces
creating effects of perceptual illusion.
   This paper explains the procedural scientific path applied to one sample of a small-
scaled theatre, but it is expected that the methodology be applied to the whole sculp-
tural heritage of the San Lorenzo Oratory.
   The restoration surveys and digital survey instrumental technologies have provided
the basis for an archival database, rich in info-graphic information, which will be useful
for future in-depth targeted analyses.


                                                                                                    293
                                                                                    The three-dimensional models created and represented in virtual reality through
                                                                                 VRML language (Virtual Reality Modeling Language), are interactively and immersive-
                                                                                 ly explorable (Figure 11).
                                                                                    From the 90s to the present day it was found that eleven statues from among the
                                                                                 sculptures populating the “small-scaled plastic theatres”, no longer existed, making the
                                                                                 reading and interpretation of the sculptural scenes from the lives of St. Francis and St.
                                                                                 Lawrence difficult and at times illegible.
                                                                                    Among future research goals, we plan to integrate the collected digital information
                                                                                 with Augmented Reality (AR) technological systems. AR is the set of technologies
                                                                                 which allow a real scene to be “augmented” [20].
                                                                                    It is a new ICT discipline at an experimental stage belonging to “computer graphics”,
                                                                                 involving the superimposition of digital contents on the observed real world.7
                                                                                    The development of an application dedicated to Serpotta’s stuccoes, usable through
                                                                                 the latest generation mobile devices (smartphones, android devices, iPads, iPods) will
                                                                                 allow the visitor to access additional contents in the form of videos or 3D models, and
                                                                                 to visualise the virtual models of the statues introduced into real scenes, in perspective.
                                                                                    The “augmented” vision will enrich the guided visit with undeniable cultural benefits,
G. Chidichimo, F. Dalena, A. Beneduci - The scenography of Serpotta stuccoes




                                                                                 enhancing the perception of the works of art with multimedia contents, pictures and
                                                                                 historical information, related itineraries, organised routes, educational information
                                                                                 about the works of art and execution processes, stucco preparation and composition,
                                                                                 restoration and consolidation work, diagnostic investigations of the decay and conser-
                                                                                 vation of the surfaces [21].
                                                                                    All this in a non-invasive way, thus helping to preserve the state of conservation of
                                                                                 the building for future generations.




                                                                                 Figure 11. “St. Francis in the act of clothing a poor man”. View in perspective of the three-
                                                                                 dimensional model, with a hypothesis of introducing the model of the stolen statue of St. Francis
                                                                                 in its original position.



                                                                                    Acknowledgments
                                                                                    The authors would like to thank the Office of Cultural Heritage of the Archiepisco-
                                                                                 pal Curia of Palermo for permitting access to the San Lorenzo Oratory. We thank Dr.
                                                                                 Maria Luisa Montaperto of the Association “Amici dei Musei Siciliani” for her regular


                                                                           294
presence during the survey. Special thanks go to Dr. Angelo Mulone, Director of the
qualified Laboratory for applied research, GeoLab of Carini (Palermo), for lending us
the equipment used in the measuring operations. We also wish to thank the digital
sculptor Davide Di Lorenzo for having actively collaborated in the organic modelling
process of the St. Francis statue.


      Notes
1
  This work presents the first results of a wider study, which is included within a National Research
Project, (PRIN 2010-2011) entitled “Architectural Perspective: digital preservation, content ac-
cess and analytics”. The Palermo unit is testing some instrumental hardware/software methods in
order to develop a path of investigation aimed at observing, building, elaborating, managing and
visualising three-dimensional models of important architectural examples of solid perspective in
Giacomo Serpotta’s scenographic sculpture.
2
  The church chamber is rich in works of art: Serpotta’s stuccoes, the beautiful marble floor crea-
ted in 1716 by the marble-workers Francesco Camalino and Alojsio Mira, the precious early 18th
century wooden stall, inlaid with ivory and mother of pearl. Unfortunately, the vault fresco of the
Martyrdom of St. Lawrence painted by Giacinto and Domenico Calandrucci between 1706 and
1708, was destroyed in the earthquake of 1823 and Caravaggio’s famous painting of the Nativity
and the Adoration of the Shepherds with St. Lawrence and St. Francis (1609) was stolen in 1969,
and are therefore missing. The complex cycle of stucco sculptures, created by Giacomo Serpotta
(1656-1732) at the height of his technical and inventive maturity (it was executed approximately
in the period between 1699 and 1706, and was partly based on the project by the architect, Gia-
como Amato), underwent restoration work in 2003.
3
  In the last decade of the 20th century, with the development of new instrumentation, the deve-
lopment of dedicated software came about, enabling computer acquisition and the elaboration
of 3D models with triangulated surface meshes or NURBS (3D imaging) with the inspection and
analysis of the latter, aimed at the creation of digital archives, the reconstruction of complex
scenarios of virtual realities (especially in the field of archaeology), and the realisation of copies




                                                                                                               CONSERVATION SCIENCE IN CULTURAL HERITAGE
through prototyping techniques.
4
  Although the technical characteristics describe an alleged non-influence of the camera angle,
it is easy to observe how rays, which are perpendicularly incident and/or not tangent, guarantee
greater final accuracy (however, working with surfaces that do not reflect).
5
  The algorithm, in fact, recognises the geometry of the object and, if the shape is “plastic” enou-
gh, as in the case in question, it allows the correct alignment of the various captured 3D frames to
visualise them in a single model (therefore conserving the reference system), eliminating as much
as possible the presence of holes and shadows due to back drafts.
6
  Some of the most popular in the field of digital 3D sculpture include, the open source software
Sculptris and the paid software ZBrush and MudBox. This panorama offers different solutions of
CAD platforms with interfaces which maximise effectiveness and flexibility of the work stream.
7
  It
  �����������������������������������������������������������������������������������������
     combines new ICT and new forms of communication, showing an incremented reality repre-
sentation in which, artificial/virtual and sensorial information is superimposed on normal visuali-
sation perceived through our senses.
8
  http://davidedilorenzo7.wix.com/davidedilorenzo.



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   Biographical notes

   Salvatore Barba, has a PhD in “Structural Engineering and Urban Restoration”; he
is associate professor at the University of Salerno in the scientific field of “Design” and
contract professor at the Polytechnic of Milan (2007-13). He has participated as invited
speaker in various conventions held in different countries, establishing scientific col-
laboration with researchers in design disciplines which are part of the UID, such as the
EGA, EGRAFIA, ABEG, INGEGRAF, SIGRADI, APEGA, ISGG. He is author of more
than eighty scientific papers; since its foundation, he has been the editor of CoPI, for
the Conference of the Deans of the Italian Engineering Faculties.

   Francesco Di Paola. An engineer with a PhD in “Representation and Surveying of
Architecture and Environment”; from 2011 he has worked as a researcher at the De-
partment of Architecture at the Polytechnic School of Palermo. He is a qualified associ-
ate professor (08/E1-Design). Since 2011 he has taught as a professor in “Architecture
Design with Laboratory”, on the Degree Course Building Engineering-Architecture.
Since 2012 he has been head of the Research Section “Digital Representation” at
the IEMEST (Euro-Mediterranean Institute of Science and Technology). His research
interests cover topics mainly in the field of Architectural Geometry, Computer Graphics,




                                                                                                    CONSERVATION SCIENCE IN CULTURAL HERITAGE
Survey, Preservation and Use of Cultural Heritage. The research results have been
the subject of more than 60 publications in scientific journals, proceedings of national/
international scientific papers and monographs.

    Giovanni Rizzo. A Chemical Engineer, he is a Professor of “Materials Science and
Technology”, Department DICAM (Civil, Environmental, Aerospace, Materials) at the
Polytechnic School of Palermo and founder of the La.Ma.RC (Materials Laboratory
for Restoration and Conservation); he is representative of the Faculty of Engineer-
ing for the Degree course in “Conservation and Restoration of Cultural Heritage” at
the Polytechnic School of Palermo. He has coordinated two editions of the Master’s
Degree STOre - “History and Technology of the Goldsmith’s art”. From 2010 to 2014
he coordinated the training project in Cambodia, Tr.In.ACRIA (Training International
Action for Conservation and Restoration of Iconographic Assets), promoted by the
University of Palermo for the training of 20 Cambodian restorers. His scientific activity
is documented by more than 150 publications in international journals and proceedings
of national and international conferences, mainly on the topics of Materials Science
and Technology applied to heritage conservation.




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