A Multidisciplinary Conservation Project for the Cavallerizza Courtyard, Palazzo Ducale Di Mantova

heritage

Case Report A Multidisciplinary Conservation Project for the Cavallerizza Courtyard, Palazzo Ducale di Mantova

Andrea Adami 1,*, Luigi Fregonese 1, Daniela Lattanzi 2, Antonio Mazzeri 3, Olga Rossignoli 1 and Barbara Scala 4,*

1 Dept. ABC (Architecture, Built Environment and construction engineering), Politecnico di Milano, Via Ponzio 31, 20133 Milano, Italy; [email protected] (L.F.); [email protected] (O.R.) 2 Segretariato Regionale del Ministero per i beni e le attività culturali per la Lombardia, Palazzo Litta-Corso Magenta 24, 20123 Milano, Italy; [email protected] 3 Complesso Museale di Palazzo Ducale di Mantova, Piazza Sordello 40, 46100 Mantova, Italy; [email protected] 4 Dept. DICATAM (Department of Civil, Environmental, Architectural Engineering and Mathematics), Università degli Studi di Brescia, Via Branze 43, 25100 Brescia, Italy * Correspondence: [email protected] (A.A.); [email protected] (B.S.)

Received: 1 April 2019; Accepted: 13 May 2019; Published: 16 May 2019

Abstract: The “Palazzo Ducale” museum complex in Mantua has been the object of intermittent interventions, which have not represented, over the last 30 years, a consistent strategy in terms of conservation. In the light of new ﬁnancial and technological possibilities, a renewed management synergy has been activated: better operative decisions and the application of innovative tools are the core of this attitude. The article illustrates the path of knowledge activated in the museum’s “Cortile della Cavallerizza”: from archival research, geometrical survey and diagnostic analysis, up to the executive design of its conservative project.

Keywords: historical analysis; conservation project; survey; BIM

1. Introduction The Palazzo Ducale complex of Mantua has been classiﬁed by d.m. 23/12/2014 (a ministerial decree regarding museums) amongst the autonomous national museums, which has been an important opportunity for taking care of the architectural complex. This has favoured a renewed process of management of its functions and of interventions in its built heritage. The interventions executed on the monument over the last 30 years have not followed a consistent conservation strategy. Direct observations of the complex and appraisals by the superintendents have shown how these operations were determined by the urgent needs of a particular time, and therefore were limited to occasional and partial actions. The availability of ﬁnancial resources has activated a management synergy for new projects, supporting restoration activities research with the application of innovative technologies. This article aims to illustrate the knowledge acquisition process in the courtyard of the Cavallerizza, inside the museum complex, up to the executive design of the conservation project.

2. The Evolution of the Building Palazzo Ducale (Figure1) presents a varied historical and architectural stratiﬁcation, strongly linked to the city life. The Gonzagas settled in Mantua from 1328 [1]. The Gonzaga [2] family promoted Renaissance culture through the contribution of important architects and painters who expressed their art within the Palazzo. With Ludovico II (1444–1478), Mantua became one of the most relevant centres of the Renaissance, giving hospitality to great artists

Heritage 2019, 2, 1441–1459; doi:10.3390/heritage2020091 www.mdpi.com/journal/heritage Heritage 2019, 2 1442

Heritage 2019, 2 FOR PEER REVIEW 2 such as Leon Battista Alberti, Luca Fancelli and Andrea Mantegna. During those years the Castle such as Leon Battista Alberti, Luca Fancelli and Andrea Mantegna. During those years the Castle of of San Giorgio and the surrounding areas became the core of the palace. Refurbishment work took San Giorgio and the surrounding areas became the core of the palace. Refurbishment work took place placein in some some rooms, rooms, to to accommodate accommodate the the Duke’s Duke’s ap apartment,artment, where where Mantegna Mantegna painted painted his famous his famous “Camera“Camera picta”. picta.”

FigureFigure 1. 1.Aerial Aerial viewview of the Cavallizza Cavallizza Courtyard. Courtyard.

DuringDuring the shortthe short regency regency of of Federico Federico I I (1478–1484), (1478–1484), the the “Domus “Domus Nova” Nova” was was started started by Fancelli. by Fancelli. His successor,His successor, Francesco Francesco II II (1484–1519), (1484–1519), dedicateddedicated himself himself toto some some works works in the in theCastle Castle such suchas as the layout of his apartment and that of his wife Isabella d”Este. The growth in fame of Mantua was the layout of his apartment and that of his wife Isabella d”Este. The growth in fame of Mantua was advanced by Isabella who, as an educated and refined patron, enriched the palace with valuable advanced by Isabella who, as an educated and reﬁned patron, enriched the palace with valuable decorations and collections. decorationsFederico and collections. II (1519–1540), son of Francesco II and Isabella d’Este, was given the title of Duke by FedericoEmperor Charles II (1519–1540), V in 1530, sonand ofbegan Francesco works in II the and Castello Isabella and d’Este, Corte Nuova, was given having the started title in of 1524 Duke by Emperora collaboration Charles V with in 1530, Giulio and Romano, began pupil works of inRaffaello the Castello Sanzio. and Corte Nuova, having started in 1524 a collaborationGiulio withRomano Giulio built Romano, the “Palazzina pupil della of Ra Paleologa”ﬀaello Sanzio. for Margherita Paleologa, wife of Federico GiulioII, and started Romano the built refurbishment the “Palazzina of one della of the Paleologa” castle’s ravelins for Margherita [3]. Paleologa, wife of Federico II, and startedHis the successor, refurbishment Guglielmo of oneGonzaga of the (1550–1587), castle’s ravelins was responsible [3]. for the regularization of the Hisspaces successor, and the connection Guglielmo between Gonzaga the apartments (1550–1587), of the was Palace responsible [4]. He started for the the regularizationrenovation of the of the spaces and the connection between the apartments of the Palace [4]. He started the renovation of the Heritage 2019, 2 FOR PEER REVIEW 3 Heritage 2019, 2 1443 PalaceHeritage and 2019 in, 2 particularFOR PEER REVIEW the “Mostra” (currently called the “Cavallerizza” garden) [5]. The managers3 of these works were the architects Giovan Battista Bertani and Bernardino Facciotto [6]. PalacePalaceFrom and and in1536 in particular particular the works the the began “Mostra” “Mostra” on the (currently(currently Rustica called(Figure the the 2), “Cavallerizza” “Cavallerizza” the southeastern garden) garden) front [5]. of [5 ]. Thethe The managersCortile managers della ofCavallerizza.of these these works works were were the the architects architects Giovan Giovan BattistaBattista Bertani and and Bernardino Bernardino Facciotto Facciotto [6]. [6 ]. FromDespiteFrom 1536 1536 the the theapparent worksworks began beganhomogeneity on on the the Rustica of Rustica the (Figure courty (Figure 2),ard, 2the), each thesoutheastern southeasternelevation front shows frontof the independence ofCortile the Cortiledella of dellaconstructionCavallerizza. Cavallerizza. in terms of thought, organization, materials and processing techniques. Only when all Despite the apparent homogeneity of the courtyard, each elevation shows independence of sidesDespite are made the isapparent an attempt homogeneity made to unify of the the design, courtyard, achieving each elevationthe current shows result. independence of constructionconstruction in in terms terms of of thought, thought, organization, organization, materialsmaterials and and processing processing techniques. techniques. Only Only when when all all sidessides are are made made is is an an attempt attempt made made to to unifyunify thethe design,design, achieving the the current current result. result.

Figure 2. Orthophoto of Rustica (elaboration of He.Su.Tech.). FigureFigure 2. 2.Orthophoto Orthophoto of Rustica (elaboration (elaboration of of He.Su.Tech.). He.Su.Tech.). From the archival documents emerges a strong sharing of ideas between the Duke and Giulio FromFrom the the archival archival documents documents emergesemerges a strong sharing of of ideas ideas between between the the Duke Duke and and Giulio Giulio Romano. The Duke always wanted to be informed about the construction activities despite the trust Romano.Romano. The The Duke Duke always always wanted wanted toto bebe informedinformed ab aboutout the the construction construction activities activities despite despite the the trust trust he placed in the architect. The concerns expressed about structural problems, difficulties in water hehe placed placed in in the the architect. architect. TheThe concernsconcerns expressedexpressed about about structural structural problems, problems, difficulties diﬃculties in inwater water management, etc., are significant. management,management, etc., etc., are are signiﬁcant. significant. TheTheThe collaborationcollaboration collaboration between betweenbetween thethe architectarchitect andandand thethe cl clientclientient solves solvessolves problems.problems. problems. In In Inparticular, particular,particular, Giulio GiulioGiulio Romano’sRomano’sRomano’s ‘trick’‘trick’ ‘trick’ isis is brilliantbrilliant brilliant andand and created createdcreated thethe opportunity opportunopportunityity toto to use useuse the thethe water waterwater to toto create createcreate fountains fountainsfountains and andand water waterwater gamesgamesgames inin in thethe the courtcourt court [[7].7 [7].]. TheTheThe “Galleria“Galleria “Galleria deidei dei Marmi”Marmi” Marmi” (Figure (Figure(Figure3 )3) is isis the thethe second secondsecond frontfront front conceived conceived by by by Giulio Giulio Giulio Romano. Romano. Romano.

FigureFigure 3. 3.Orthophoto Orthophoto ofof thethe Galleria dei dei Marm Marmii (elaboration (elaboration of of He.Su.Tech.). He.Su.Tech.). Figure 3. Orthophoto of the Galleria dei Marmi (elaboration of He.Su.Tech.). The work of adapting the spaces is interesting. The spans are not regular but their succession does not emerge from the dimensional diﬀerences necessary to give a proper solution corner. If in the

Heritage 2019, 2 FOR PEER REVIEW 4 Heritage 2019, 2 FOR PEER REVIEW 4 The work of adapting the spaces is interesting. The spans are not regular but their succession Heritage 2019, 2 1444 doesThe not workemerge of fromadapting the dimensionalthe spaces is differencesinteresting. ne Thecessary spans to are give not a regularproper solutionbut their corner. succession If in doesthe Rustica not emerge the solomonic from the columnsdimensional emerge differences from a solid necessary rusticated to give wall, a proper here they solution flank thecorner. arches If inof theRusticathe Rusticaoriginal the thesolomonic Loggia. solomonic Compared columns columns to emerge the emerge seven from from arches a solid a solid of rusticated the rusticated Rustica, wall, here wall, here there here they are they flank eight. flank the It the archesis interesting arches of the of theoriginalto noteoriginal the Loggia. Loggia.difference Compared Compared in height to to the between the seven seven archesthe arches floor of of theelevations the Rustica, Rustica, of here herethe thereGallery there are are of eight. eight. the Marbles ItIt is interesting and the to“Galleria note the della difference diff erenceMostra” in (Gallery height betweenof the Exhibition): the floorfloor elevationsif it corresponds of the to Gallery the level of theof the Marbles windowsill and the for “Galleria“Galleriathe former, delladella it equals Mostra”Mostra” the (Gallery(Gallery floor level ofof thethe for Exhibition):the latter [7]. if Init corresponds the “Galleria to della the level Mostra,” of the after windowsill the death for of theGiulio former, Romano, it equals the thearchitect floorfloor levellevelBertani for tried thethe latterlatter to intr [[7].7oduce]. In the different “Galleria solutions della Mostra,” Mostra”, from those after conceived the death byof GiulioGiulio Romano, Romano[8]. the However, architect Bertani not the triedarchival to intr introducedataoduce but the different diff informationerent solutions obtained from thosein the conceived restoration by of Giuliothe early Romano[8]. Romano 20th century [8]. However, However, have clarified not not the the thearchival archival construction data data but but (Figure the the information information 4) [9]. obtained obtained in the restoration of the early 20th century have clarifiedclarified the construction (Figure(Figure4 4))[ 9[9].].

Figure 4. Orthophoto of La Galleria della Mostra (elaboration of He.Su.Tech.). Figure 4. OrthophotoOrthophoto of of La La Galleria Galleria della della Mostra Mostra (elaboration of He.Su.Tech.). The “Corridore” is the front that closes the court. Our observations provide interesting informationThe “Corridore”“Corridore” on its construction is theis the front front that (Figure closesthat closes the5). court.The the di Ourrectcourt. observationsexamination Our observations provide (on the interesting occasionprovide informationofinteresting the first informationonrestoration) its construction ofon theits masonry (Figureconstruction5). confirms The (Figure direct the 5). examinationhypoth The diesisrect that (on examination the new occasion loggia (on of the was the occasion ﬁrstbeing restoration) added of the to first ofthe restoration)theexisting masonry city of walls. conﬁrms the masonryThe the pillars hypothesis confirms of the external thatthe thehypoth side new ofesis loggia the that portico was the being newhave loggia addedbeen obtained was to the being existing “by added subtraction,” city to walls. the existingThethat pillars is, bycity ofdemolishing walls. the external The pillars as side many of of the the wall portico external sections have side as been ofthere the obtained wereportico arches “by have subtraction”, demolishingbeen obtained that the is,“by thickness by subtraction,” demolishing of the thatthewall. thickness is, In by the demolishing ofdemolition, the wall. as In manyarches the demolition, wall were sections obtained. arches as there wereOn the obtained.were contrary, arches On demolishing thethe contrary, inner side the the thickness innerof the side porch of of the is wall.porchcompletely In is completelythe new. demolition, From new. the Fromarches outside the were outsideof the obtained. courtyard of the courtyardOn the the anchoring contrary, the anchoring ties the are inner evident, ties are side evident, positioned of the positioned porch to weld is completelytothe weld two theparts new. two into partsFrom a single into the aoutsideresistant single of resistant element. the courtyard element. the anchoring ties are evident, positioned to weld the two parts into a single resistant element.

FigureFigure 5.5. View ofof thethe lakeshorelakeshore Loggia.Loggia. Figure 5. View of the lakeshore Loggia. The documentation of the restoration work was particularly useful for setting up the conservation project. Within the logic of Programmed Conservation, as our work is intended to be, knowledge of modern restoration work plays a fundamental role. Also, the information preserved through a

Heritage 2019, 2 1445 photographic documentation allowed us to georeference the interventions carried out and to know in detail the materials used in the restoration. From 1866 the conservation status of the Cavallerizza was monitored with greater precision. Achille Patricolo was the curator of the building. Despite the attention and the desire to reorganize the management of the building promoted by Patricolo, in 1908 the Cortile della Mostra was used as a tennis court, with negative consequences on the decorative apparatus because of such improper use. Attempts to give continuity to the maintenance were hindered by circumstances rather than by the will of those responsible. Alfredo Barbacci (responsible from 1936 to 1939) offered an interesting statement on the conservation status of the Cortile della Cavallerizza. The architect described its precarious conservation conditions due to the use of the internal garden as a vegetable garden. In particular, Barbacci underlined how the plasticity of the rustication was decidedly compromised and the colours almost invisible. A first construction site led by Barbacci began in 1936 and concerned the Rustica elevation. It is interesting that he observed how the plastic ornaments were still present but detached from the wall support (Barbacci, 1939). The operational choice proposed by Barbacci was to consolidate them with injections of “liquid mortar”. The missing plaster and ashlars were reintegrated in imitation of the originals (by giving them an antiqued effect). Only for the Solomonic columns did Barbacci propose a non-imitative approach, as demonstrated by the fact that the decorations simulating vine shoots were not re-proposed but the surface was kept smooth. The last “unitary” construction (that is, managed with the same criteria of intervention) took place between 1937 and 1938 and concerns the Corridore towards the lake; the infills of the ground floor arches were demolished and the railings placed. Even on this side the ashlars were “integrated”, such as the plaster on the first and second order. Barbacci also described the original colours of the ashlar: slightly muted yellow, red and grey. Only in the 1980s were new interventions on the external surfaces implemented, with projects that were consistent with the peculiarities of the place. That projects drafted by the Superintendency of Brescia. Unfortunately, from the surveys stored in the archive, it is not always possible to identify precisely the areas of intervention, because the drawings accompanying the appraisals are generic and do not clarify whether the described procedure has been uniformly performed. A second period of work on the surfaces began in 1994, on the initiative of Ruggero Boschi, Superintendent for environmental and architectural assets for Mantova Brescia and Cremona. This last project was a turning point in the management of the built environment, agreeing with present-day positions on the matter. Among the documents, there is a certificate of the chemical-physical investigations aimed at identifying the materials present. The techniques and degradation factors are also indicated. The appraisal envisaged (as an intervention rule) wet cleaning with a nebuliser (AB-57) or localized aeroabrasives. For consolidating, Primal AC-33 (Perugia, Italy) diluted in demineralized water was used. The reconstruction of the ashlars was done with a mixture of lime, aggregates and pigments with slightly subdued colours compared to those detected. The entire surface was then treated with a water-repellent final protective layer.

3. Preliminary Analysis The conservation project is the result of a collaboration between the Complesso Museale di Palazzo Ducale di Mantova, the He.Su.Tech group of Mantovalab of the Politecnico di Mantova, and the Centro per la Conservazione e il Restauro dei Beni Culturali “La Venaria Reale”. Each institution provided its own skills. Heritage 2019, 2 FOR PEER REVIEW 6

3.1. The Survey To guarantee a more extensive knowledge of the Cortile della Cavallerizza and its connected parts, a survey was carried out through the integration of the most recent methodologies and instruments in the field of geomatics. The survey phase has followed the general principle that characterizes the geomatic discipline, a top-down approach that requires one to start from the general and then move to details. The framework of the survey is, as in best practice, made up of a topographic network that not only materializes the reference system (unique for the entire complex to be surveyed) but facilitates the integrationHeritage 2019, 2of different methods. The network is the skeleton of the whole survey to which all 1446the other surveyed elements are directly connected and referred. The materialization of the topography was the first task to complete following the top-down methodology described: it was framed in the national3.1. The Surveyreference system IGM95 thanks to the acquisition of two national Ground control point (one in PiazzaTo guarantee Sordello a moreand the extensive second knowledge on the lake of the shore). Cortile This della structuring Cavallerizza allows and its at connected any time parts, the integrationa survey was of carriednew information out through acquired the integration at different of the times most and recent stages methodologies and ensures and comparison instruments with in thethe national field of geomatics. cartographic products. DetailedThe survey topographic phase has acquisitions followed the for general the survey principle of the that architectural characterizes complex the geomatic followed, discipline, where observationsa top-down approach were made that requires starting one from to start the from prin thecipal general points and thenof the move network, to details. to The support framework the photogrammetricof the survey is, asand in bestlaser practice, scanning made surveys. up of aGenerally, topographic the network points thatsurveyed not only with materializes a Leica Geosystemsthe reference AG system - Part (unique of Hexagon, for the Huntsville, entire complex [AL], USA to be TC30 surveyed) total station but facilitates were the the black integration and white of chessdifferent target methods. (for the The registration network isof thethe skeletonlaser data) of theand whole the code survey markers to which (for allthe the photogrammetric other surveyed phase).elements The are results directly obtained connected after andthe least referred. square The ad materializationjustment (the coordinates of the topography of the points) was have the first an averagetask to completestandard deviation following of the less top-down than ± 1 mm methodology and are therefore described: suitable it was for framedthe 1:50 inscale the survey national of thereference entire systemcomplex IGM95 of the thanks Cavallerizza. to the acquisition of two national Ground control point (one in Piazza SordelloIn the and survey the second of the oncourtyard the lake (including shore). This the structuringwall surfaces allows and the at any gallery) time it the was integration decided to of integratenew information laser scanner acquired with atphotogrammetry different times and(Figure stages 6) in and order ensures to have comparison a complete with dataset the that national met bothcartographic the needs products. of a geometric description of the building (for the architectural survey) and its qualitativeDetailed description, topographic from acquisitionswhich to extract for information the survey related of the to architectural the materials complex used and followed,the state ofwhere preservation. observations were made starting from the principal points of the network, to support the photogrammetricThe laser scanner and lasersurvey scanning was carried surveys. out by Generally, the phase the shift points Leica surveyed HDS 7000, with and a Leica made Geosystems it possible toAG—Part describe ofthe Hexagon, interior of Huntsville, the courtyard, [AL], as USAwell asTC30 the totalCorridore station passing were thethrough black it andand whitethe exterior chess facingtarget (forthe thelake registration (Figure 7). of A the total laser of data)26 scans and thewere code taken, markers on several (for the levels photogrammetric and from different phase). positions,The results setting obtained the afterresolution the least to squarean average adjustment value of (the 3 m coordinates at a 10 m distance of the points) to ensure have a andensity average of pointsstandard suitable deviation for the of lessscale than of re1presentation mm and are 1:50 therefore (in fact, suitable given forthe theoverlap 1:50 scale of data, survey the ofdatabase the entire of ± pointcomplex clouds of the also Cavallerizza. became suitable for the extraction of drawings at the 1:20 scale). The scans were georeferencedIn the survey in Leica of the Cyclone courtyard software (including using the the wall coordinates surfaces and of the the gallery) targets it measured was decided with to topography.integrate laser At scanner the end with of the photogrammetry acquisition phase, (Figure a 6single) in order database to have was a completecreated, and, dataset through that Autodeskmet both theRecap, needs San of Rafael, a geometric [CA], USA description , the data of were the building imported (for into the the architectural Autocad environment survey) and and its digitized.qualitative description, from which to extract information related to the materials used and the state of preservation.

Figure 6. Digital photocomposition to describe the diﬀerent stages of the geometric survey, from the point cloud (in greyscale on the left), to the orthophoto (centre) to the vector drawing (on the right).

The laser scanner survey was carried out by the phase shift Leica HDS 7000, and made it possible to describe the interior of the courtyard, as well as the Corridore passing through it and the exterior facing the lake (Figure7). A total of 26 scans were taken, on several levels and from di ﬀerent positions, setting the resolution to an average value of 3 m at a 10 m distance to ensure a density of points suitable for the scale of representation 1:50 (in fact, given the overlap of data, the database of point clouds also became suitable for the extraction of drawings at the 1:20 scale). The scans were georeferenced in Leica Cyclone software using the coordinates of the targets measured with topography. At the end of the acquisition phase, a single database was created, and, through Autodesk Recap, San Rafael, [CA], USA, the data were imported into the Autocad environment and digitized. Heritage 2019, 2 FOR PEER REVIEW 7

HeritageFigure2019, 2 6. Digital photocomposition to describe the different stages of the geometric survey, from the 1447 point cloud (in greyscale on the left), to the orthophoto (centre) to the vector drawing (on the right).

SimultaneousSimultaneous to to the the laser laser scanner scanner survey,survey, aa photogrammetricphotogrammetric campaign was was carried carried out, out, based based onon “structure “structure from from motion”motion” andand “dense“dense stereo matc matching”hing” algorithms. algorithms. To To obtain obtain the the best best results, results, a a high-resolution camera Canon, To Tokyo,kyo, Japan Mark Mark III III was was used used with with different different lenses lenses (24 (24 mm, mm, 35 35 mm mm andand 85 85 mm). mm). The The di differentfferent lenses lenses allowed allowed usus toto maintainmaintain for each element element of of the the site site (facades, (facades, ceilings ceilings andand vaults) vaults) an an average average GSD GSD of of less less thanthan 11 mmmm in order to process process the the photog photogrammetricrammetric products products with with a finala final real real pixel pixel size size of of 5 5 mm. mm. TheThe acquisitions acquisitions werewere mademade followingfollowing thethe logiclogic of the photogrammetric strip, strip, but but with with a a longitudinallongitudinal and and transversal transversal overlap overlap of aboutof about 70–80% 70–80% to allow to allow greater greater recognition recognition of significant of significant points points to be used in the orientation phase. In addition to the frames normal to the facade, used in the to be used in the orientation phase. In addition to the frames normal to the facade, used in the strip, strip, frames with an inclined axis were acquired, with the aim of stiffening the acquired geometry; frames with an inclined axis were acquired, with the aim of stiffening the acquired geometry; this was this was also dictated by the elongated and homogeneous geometric shape of the building itself, also dictated by the elongated and homogeneous geometric shape of the building itself, which could which could have led to drift effects. Also, in the case of photogrammetry, targets (encoded by the have led to drift effects. Also, in the case of photogrammetry, targets (encoded by the software Agisoft software Agisoft Photoscan St. Petersburg, Russia—now Metashape) were acquired by topographic Photoscan St. Petersburg, Russia—now Metashape) were acquired by topographic means that allowed means that allowed us to georeference the photogrammetric model in the same system. The us to georeference the photogrammetric model in the same system. The photographic acquisition was photographic acquisition was carried out on several levels to try to overcome the undercuts caused carried out on several levels to try to overcome the undercuts caused by the rustication and decorative by the rustication and decorative elements; the photos acquired are of the Exhibition Gallery, the elements;Galleria thedei photosMesi, and acquired by the areCorridore of the Exhibition (the lakesh Gallery,ore Loggia) the Galleria that separates dei Mesi, the and courtyard by the Corridorefrom the (thelake. lakeshore Loggia) that separates the courtyard from the lake.

FigureFigure 7. 7. TheThe lakeshorelakeshore loggia described described by by different different survey survey outcomes: outcomes: two two transversal transversal sections sections (S1 (S1and and S2), S2) the, the orthophoto orthophoto of of the the façade façade (centre) (centre) and and the the opposite opposite map map of of the the ground ground floor floor (centre (centre bottom)bottom) and and first first floor floor ceiling ceiling (centre (centre top). top).

AtAt the the end end of of the the acquisition acquisition phase,phase, allall thethe datadata (as(as mentioned above, above, included included in in a asingle single georeferencedgeoreferenced database) database) were were imported imported inin thethe AutocadAutocad environment and and the the design design was was carried carried out out atat a scalea scale of of 1:50 1:50 (Figure (Figure8). 8). At At the the same same time, time, the the orthophotos orthophotos ofof thethe facadesfacades (internal and and external) external) andand of of the the false false ceilings ceilings of of the the Lakeshore Lakeshore LoggiaLoggia (Figure(Figure7 7)) werewere alsoalso processed,processed, not only to to obtain obtain a a productproduct to to be be used used in in the the geometric geometric descriptiondescription ofof thethe factory, but also to support support the the analysis analysis of of the the materialsmaterials and and degradation. degradation.

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FigureFigure 8. 8.TheThe final ﬁnal outcome outcome of of the the Rustica Rustica at at the the scale of 1:50: the elaborationelaboration is is the the overlapping overlapping of of the the OrthophotoOrthophoto and and the the vector vector draft. draft.

TheThe processing processing thus thus obtained obtained allowed allowed the the comparison comparison ofof technologicaltechnological and and decorative decorative elements, elements, leadingleading to toan an interpretation interpretation of of the the complex complex based based not onlyonly onon archivalarchival documents, documents, but but also also on on the the continuouscontinuous material material feedback feedback of of what what is is highlighted highlighted inin thethe papers.papers. The survey carried out revealed the numerous details of both the individual fronts and, in particular, The survey carried out revealed the numerous details of both the individual fronts and, in the individual technological elements. We considered it very significant to highlight these singularities particular, the individual technological elements. We considered it very significant to highlight these because a conservation project aims precisely to preserve diversity, highlighting the solutions that singularities because a conservation project aims precisely to preserve diversity, highlighting the are expressions of construction practice. The analysis being carried out at an autopsy level, which solutions that are expressions of construction practice. The analysis being carried out at an autopsy highlighted the wealth of construction and restoration solutions, was why chemical-physical studies level,were which carried highlighted out. the wealth of construction and restoration solutions, was why chemical‒ physicalIn studies order to were optimize carried indirect out. investigations, direct reconnaissance has optimized the time involved, helpedIn order to confirm to optimize hypotheses indirect andopened investigations, up new avenues direct ofreconnaissance investigation. has optimized the time involved,The helped first aspect to confirm investigated hypotheses concerns and the opened rustication, up new the finishingavenues solutionof investigation. that offers unity to the courtyardThe first of aspect the Cavallerizza investigated and concerns at the same the time rustication, is the technique the finishing with many solution finishing that offers solutions. unity to the courtyardFour di offferent the Cavallerizza types of finishing and at are the visible same along time theis the pillars technique that support with many the arches: finishing solutions. Four different types of finishing are visible along the pillars that support the arches: rustication made with solid bricks in which the irregular shape of the surface is given by the • thickness● rustication of the mortar made properly with engravedsolid bricks and in worked; which the irregular shape of the surface is given rusticationby made the thickness from solid of bricks the mortar in which properly the irregular engraved shape and of the worked; surface is given by roof-tile • fragments● rustication covered with made lime from mortar; solid bricks in which the irregular shape of the surface is given rusticationby made roof-tile from fragments solid bricks covered in which with the irregular lime mortar; shape of the surface is given by fragments • and flakes● rustication of brick covered made withfrom lime solid mortar. bricks in which the irregular shape of the surface is given ashlars madeby fragments of solid bricks and in flakes which of the brick shape covered of the surfacewith lime is given mortar. by the sinuous shape of the • bricks● (s-shaped). ashlars made of solid bricks in which the shape of the surface is given by the sinuous shape of the bricks (s-shaped). During the restorations, other types of rustication, similar to the first model, yet realized with cementDuring mortar the restorations, and with non-repeated other type randoms of rustication, shapes, were similar performed. to the first model, yet realized with cementOn mortar the ground and with floor, non-repeated at the springer random of the arch,shapes, there were are performed. three other types of rustication: On the ground floor, at the springer of the arch, there are three other types of rustication: ashlars with a very irregular finish (placed on the top of the pillars as a springer of the arches); • ashlars● withashlars irregularities with a very about irregular one centimetre finish (placed deep (placed on the to top form of the the arc). pillars as a springer of • the arches); ● ashlars with irregularities about one centimetre deep (placed to form the arc).

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ashlars with small irregularly distributed holes (the small holes were probably made with iron or • ● ashlars with small irregularly distributed holes (the small holes were probably made wood punches)with to iron enrich or wood the heterogeneity punches) to enrich of the finishthe heterogeneity (placed between of the the finish arches (placed and between the frame along differentthe sides). arches and the frame along different sides). ItIt should should be be noted noted that that both both the the surface surface treatment treatment of the of mortarthe mortar and theand juxtaposition the juxtaposition of the of ashlars the presentashlars dipresentfferences differences between between the parts the attributed parts attrib touted Giulio to RomanoGiulio Romano and those and referablethose referable to Bertani. to SomeBertani. gaps Some in the gaps south in the elevation south elevation allow us allow to investigate us to investigate the executive the executive technique technique used by used the workersby the underworkers the under guidance the guidance of Giulio of Romano. Giulio Romano. On this front,On this the front, combination the combination of bricks of and bricks the and use the of larger use fragmentsof larger fragments in the upper in the part upper of the part ashlar of the is visible.ashlar is visible. AnotherAnother element element of of di ffdifferentiationerentiation between between the workthe work of the of two the masters two masters is in the is plaster in the processing. plaster processing.These di fferences are determined by the type of effect sought: These differences are determined by the type of effect sought: a bocciarda, to obtain rounded depths of variegated dimensions • ● a bocciarda, to obtain rounded depths of variegated dimensions a serpentina, to draw tracks between the holes created with the bocciarda. • ● a serpentina, to draw tracks between the holes created with the bocciarda. InIn the the spans spans attributed attributed toto GiulioGiulio Romano’s work workshop,shop, the the ashlars ashlars show show a amore more decorative decorative style. style. WeWe can can find find ashlars ashlars worked worked alternatelyalternately withwith a finefine bocciarda technique technique and and ashlars ashlars worked worked with with a a coarsercoarser style style (Figure (Figure9 ).9).

FigureFigure 9.9. DetailDetail photo with evidence of of the the bocciarda bocciarda technique. technique.

InIn the the spans spans of of the the northern northern elevation elevation attributed attributed to the to Giovanthe Giovan Battista Battista Bertani Bertani construction construction phase, diphase,fferent different workmanship workmanship is highlighted, is highlighted, characterized characterized by a more by a pronounced more pronounced chiaroscuro chiaroscuro effect andeffect the concomitantand the contemporary use of serpentina concomitant and bocciarda. use of serpentina and bocciarda. AnAn interesting interesting detaildetail isis aa falsefalse ashlarashlar painted on the plaster plaster in in the the north north elevation, elevation, on on which which a a subsequentsubsequent mortar mortar ashlar ashlar was was then then applied. applied. The The plaster plaster finish finish was was tapped tapped on on the the decorated decorated surface surface to ensureto ensure the adhesionthe adhesion of such of such superficial superficial ashlar ashlar (Figure (Figure 10 ).10).

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FigureFigure 10.10. Detail with different diﬀerent ashlars. ashlars.

TheThe string-course string-course frame frame is formed is formed by quadrangular by quadrang panels,ular panels, slightly slightly protruding. protruding. To give movementTo give tomovement the panels, to small the panels, holes were small carved, holes were similar carved, to those similar on theto those lower on ashlars. the lower For theashlars. completion For the of thiscompletion frame the of bases this frame of the the twisted bases columns of the twisted are characterized columns are bycharacterized a fake pebble by finish.a fake pebble Each base finish. is an elementEach base in itself; is an theelement number in itself; and the distribution number and of thedistribution pebbles isof apparently the pebbles random. is apparently random. OnOn the the main main floor, floor, adjacent adjacent to to thethe SolomonicSolomonic colu columns,mns, the the ashlars ashlars offer offer formal formal solutions, solutions, similar similar toto those those illustrated illustrated up up until until now. now. TheThe greatest greatest diversification diversification is is found found in in their their greater greater or or lesser lesser projection projection and and by by the the presence presence of of the perimetralthe perimetral ribbon. ribbon. In particular, the northern façade presents ashlars with a rectangular and regular shape, while In particular, the northern façade presents ashlars with a rectangular and regular shape, while the the south façade shows, in the vicinity of the openings, thicker ashlars, projecting towards the south façade shows, in the vicinity of the openings, thicker ashlars, projecting towards the courtyard. courtyard. While the former were treated during the last restoration with yellow and grey finishing While the former were treated during the last restoration with yellow and grey finishing colours, colours, the latter are exclusively in grey. the latter are exclusively in grey. Other ashlars used to decorate the tympanums above the windows of the first floor have a differentOther ashlarsplaster processing used to decorate on both the the tympanums façade realized above by theGiulio windows Romano of and the that first of floor Bertani. have a diffElementserent plaster in worked processing mortar on have both also the façadebeen used realized to fill by the Giulio spaces Romano between and the that bases of Bertani.of the columns Elements inwith worked quadrangular mortar have panels also and been a diamond-point used to fill the el spacesement. Moreover, between the the basesones on of thethe columnssides of the with quadrangularwindows are panels arranged and in a staggered diamond-point rows so element. that some Moreover, of the blocks the onescome on out the from sides the of background the windows arewall. arranged in staggered rows so that some of the blocks come out from the background wall. TheThe data data on on the the ashlars’ashlars’ mortarsmortars revealreveal a correspondence between between the the composition composition and and granulometrygranulometry of of thethe aggregates, suggesting suggesting a cont a continuityinuity between between the phase the phase of Giulio of Giulio Romano Romano and andthat that of ofGiovan Giovan Battista Battista Bertani. Bertani. TheThe mortars mortars are are constituted constituted by anby aerialan aerial lime enrichedlime enriched with awith carbonate a carbonate and, in and, smaller in quantities,smaller silicatequantities, aggregate. silicate This aggregate. mortar This forms mortar the ashlar forms plaster the ashlar on whichplaster a on coating which has a coating been applied has been in an imitationapplied ofin colouredan imitation stones. of coloured stones. InIn the the case case of of ashlar, ashlar, colour colour has has thethe functionfunction of emphasizing the the frame frame made made by by an an alternation alternation ofof yellow-red yellow-red or or grey-yellow grey-yellow ashlars,ashlars, whichwhich are reminiscent reminiscent of of the the coloured coloured stones stones used used in inthe the MantuanMantuan constructions. constructions. ClearClear traces traces of greenof green polychromy polychromy are are observed observed in thein ashlarsthe ashlars of the of Rustica.the Rustica. Ontop Onof top this of coating, this coating, traces of a further (more recent) yellow layer were found. traces of a further (more recent) yellow layer were found. In the remaining façades, the ashlars have a polychromy that alternates red and yellow. In the In the remaining façades, the ashlars have a polychromy that alternates red and yellow. In the western elevation, in particular, the stratigraphy comprises three levels: western elevation, in particular, the stratigraphy comprises three levels: • the first consists of a dark red colour, partially preserved; the first consists of a dark red colour, partially preserved; • • the second, a red tint applied generically to the whole surface, is based on white with ochre the second, a red tint applied generically to the whole surface, is based on white with ochre and/or • and/or red earth; red earth;

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•the the third third is light is light pink pink and and applied applied in a in localized a localized way. way. • The yellow ashlarsashlars consistconsist ofof two two layers, layers, a a dark dark yellow yellow in in the the background background and and a lighter a lighter one one in the in thefront. front. It is It possible is possible that that the twothe bottomtwo bottom layers layers are the are result the result of the of same the intervention,same intervention, during during which whichtwo di fftwoerent different shades shades would would have been have used. been used. The layout layout of of the the elevations elevations in the in thenoble noble floor floor is marked is marked by the by iconic the Solomonic iconic Solomonic columns columns (Figure 11).(Figure 11). The role of the the columns columns is is to to define define the the subdivision subdivision of the the spans, spans, which, which, contrary contrary to to what what appears appears at first first glance, is irregular, not only betweenbetween didifffferenterent frontsfronts butbut alsoalso withinwithin thethe samesame front.front. The base level of the columns is clearly not the same on all four sides. Along Along the the northern northern front, front, theythey are are set at the level of the windowsill; on the other sides, the columns lay lay out the entire noble floor,floor, starting from the level of the indoor pavement pavement.. The decorative decorative trick guaranteed by the twisting distracts the observer from the geometric irregularity of the span pace.

FigureFigure 11. 11. AA comparison comparison of of the the different diﬀerent columns of the courtyard.

There are numerous elements of didiffefferentiationrentiation betweenbetween thethe columns:columns: 1. the columns1. the of columns the side ofof the the Rustica side of appear the Rustica thinner appear and have thinner a more and sinuous have movementa more sinuous of the rings, whilemovement the shaft ofof thethe columnsrings, while of the the longer shaft of sides the arecolumns thicker; of the longer sides are thicker; 2. only the2. columnsonly the of columns the south of elevationthe south areelevation entwined are withentwined vine shoots,with vine while shoots, in the while rest in of the elevations vines,rest of bunchesthe elevations of grapes vines, and bunches other types of grapes of leaves and are other mixed types up; of leaves are mixed 3. some of theup; vine shoots run along the flutings, following a straight line (in some columns of the south elevation),3. some of while the othersvine shoots follow run a sinuous along linethe (especiallyflutings, following in the north a straight and west line elevations); (in some 4. the columnscolumns in the westof the and south north elevation), elevations while present others two follow branches a sinuous that constantlyline (especially intertwine, in the drawing ovalnorth shapes; and west elevations); 5. the vine4. leavesthe columns of the south in the elevation west and are north more elevatio simplified;ns present in other two elevations, branches that where constantly various types of leavesintertwine, appear drawing (combined oval with shapes; bunches of grapes), the element acquires greater detail and volume;

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6. in the east and west elevations, towards the north side, the intertwining of flowers and leaves consists of a main branch on which a finer floral branch is wrapped.

It should be emphasized that the possible non-presence of stucco decoration does not mean that it had not been there previously. The columns have been the subject of restorations in which it was preferred not to proceed with the integration of the gaps in the floral decoration, by choosing to close them with smooth plaster. The architectural element is realized in bricks, shaped and covered with several layers of mortar and a final stucco coating on which the floral decoration is applied, adjusted and remodelled in situ. The internal brick body of the columns is made of bricks subsequently covered with layers of a mixture of lime and aggregates to build the body of the column. A subsequent layer completed the curvature profile. From the executed stratigraphies, it emerges that the final layer is a fine stucco with colour residues now preserved in small traces. In the east elevation, a further layer of colour applied on this last one is present: a sort of rosy plastering consisting of three other layers: a white-pinkish outer layer, a white layer and a grey inner layer. A trace of red pigmentation has been observed in a column of this front. In the east elevation, a red-earth and/or red ochre laying has been identified. The discovery could confirm the existence of an ochre polychromy on the surface of the columns of the elevation realized by Bertani. The string-course frames are made by laying a double course of bricks placed in the shiner orientation and covered with a smooth, almost polished lime-based plaster. The glossy finish also characterizes the lintel above the windows made of bricks. The shelves of the columns are made of layers of bricks arranged to create the curved S-shape ending with an upper horizontal plane. From the investigations conducted during restoration works, the presence of iron structural elements to support the overhang did not emerge. Probably, the masonry is made exclusively of protruding bricks covered with fractured plaster to create a rough surface. The upper entablature repeats the classical scheme of metopes and triglyphs and constitutes a further useful element to give a sense of unity to the courtyard. However, comparing the sequence of triglyphs, pyramids, dentils and bas-reliefs (made both with moulds and freehand), we notice a rich variety of design and workmanship. The elevated position contributed to a better preservation of the finish so that traces of colour were seen on all sides. The execution technique of the entablature is observable from some gaps in the mortar. The brickwork is covered by a fine polychrome stucco with which both the decorative elements (triglyphs) and the scenes inside the metopes are modelled. The dentils were made with the same technique: a rowlock brick is covered with two layers of mortar and one layer of stucco. Other elements, such as the ovoli decoration frame, were instead made by means of a mould, as can be seen from the mark left between the elements. In the bas-reliefs inside the metopes, the moulding technique is combined with freehand execution, based on a charcoal reference drawing. In many scenes there are visible iron nail heads, used to ensure the anchoring of the projected portion of the masonry. Other metallic elements were inserted into the metopes to anchor objects or fabric on festive days. In the metopes of the south and east façade, the workers realizing the decorations used a shared reference drawing, which served as a guide for the application of the stucco. For the realization of the bas-reliefs, two types of mixture were used, a lime-based mortar with a coarser grain size and a fine-grained, white stucco. The first type of mixture was used only in bas-reliefs (made by applying layers of material with the help of a special tool). Instead, the stucco was used in bas-reliefs, executed both freehand and with the moulding technique, then later applied to the background of the metope. Heritage 2019, 2 FOR PEER REVIEW 13

HeritageInstead,2019, 2 the stucco was used in bas-reliefs, executed both freehand and with the moulding1453 technique, then later applied to the background of the metope. The whole entablature presents a combination of yellow, red and purple that correspond to variousThe interventions, whole entablature carried presents out over a combination small portions of yellow, or large red areas. and purple that correspond to various interventions,To better carriedunderstand out over the colorimetric small portions aspect or large of the areas. frame, the investigations carried out by the ICR wereTo better useful. understand The results the colorimetricof the XRF analyses, aspect of thecarried frame, out the uniformly investigations on the carried Cavallerizza out by the fronts, ICR wererevealed useful. the Thepresence results of of chromium the XRF analyses, traces (proba carriedbly out chromium uniformly onyellow) the Cavallerizza and of zinc fronts, and titanium revealed the(probably presence white). of chromium This confirm traces the (probably hypothesis chromium that there yellow) was and a ofyellow zinc andlayer titanium over the (probably whole white).entablature. This confirm the hypothesis that there was a yellow layer over the whole entablature. Under these levels, in the background of the metopes, different different stratigraphies are present depending on which of the spans they are on. Observation and study of corner solutions help us to understand the architectural structure (Figure 1212).). The portion facing the lake was placed over the body of the Rustica, previously built by Giulio Romano. The junction between the inner wall of the Corridore and the Rustica shows a single half-column. The pilasterpilaster thatthat completed completed the the facade facade of of the the Rustica Rustica was was hidden hidde byn thisby this front front (it can (it justcan bejust seen be seen from from the mainthe ma floorin floor of the of loggia).the loggia).

Figure 12. Corner solution of the upper part (image on left: 1989) and of the lower part (today).

In the lower register, the pillar of the first first arch on the lake side, inevitably, is embedded into the opening of the Rustica arcade. This inconsistency was corrected by inserting a further inner arch into this firstfirst spanspan onon the the left. left. The The expedient expedient determines determines the the creation creation of of an an angular angular pillar pillar that, that, if it if does it does not completelynot completely conceal conceal the anomaly,the anomaly, at least at least attenuates attenuates its evidence. its evidence. In the the opposite opposite corner, corner, at atthe the junction junction between between the Rustica the Rustica and the and Galleria the Galleria della Mostra, della the Mostra, pre- theexisting pre-existing old masonry old masonrydoes not doeshinder not the hinder presence the of presence a rustic of pillar a rustic supporting pillar supporting the last walled-up the last walled-uparch of the archarcade. of the Above, arcade. a half-column Above, a half-column is aligned with is aligned the underlying with the underlying pillar. The pillar.Gallery The intersects Gallery intersectsthe Rustica the laterally Rustica with laterally respect with to respectthe spiral to thehalf-column. spiral half-column. On the upper floor,floor, the semi-column resting on thethe Galleria side approaches (because of its projection) the corresponding RusticaRustica column,column, creatingcreating coupledcoupled cornercorner columns.columns. In thethe other other corners corners of theof Courtyardthe Courtyard the appearance the appearance is much is more much regular. more In regular. fact, the enlargementIn fact, the ofenlargement the original of Loggia the original in the Galleria Loggia dei in Marmithe Galler wasia designed dei Marmi to avoid was thedesigned lack of symmetryto avoid the so obviouslack of onsymmetry the opposite so obvious side. on the opposite side.

3.2. State of Conservation

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3.2. State of Conservation The state of conservation of the surfaces was defined through a direct reading of the building and a diagnostic project. The investigations were carried out by means of X-ray fluorescence analysis (XRF), Fourier Transform Infrared Spectrophotometry (FTIR), X-ray Diffraction (XRD) and Aqua-boy analysis. From the verification carried out, the state of conservation of the work is not sufficient. The surfaces present serious degradation that manifests itself in various forms: cracking, de-cohesion, erosion, exfoliation, loss of material, stains and coherent and incoherent deposits. The mortars used to supplement previous interventions are no longer cohesive. The metallic elements necessary for anchoring fragmented surfaces are now compromised. The degradation phenomena are widespread in the south and east elevations, more specifically on the lower parts of the rusticated ashlar, on the columns towards the corners and on the frame above the frieze. The mortars of the ashlar masonry and of the inner layers of the columns present a more serious state of degradation. This is due to the composition and mineralogical genesis of the mortars and to the restoration interventions that have made use of cement mortars. In general, large deposits of pigeon guano, honeycombs and spider webs located in the undercuts of the entablature are evident. Copious and tenacious atmospheric particulate deposits are abundant in the east elevation and in the corners of the remaining elevations. On every carved surface, the atmospheric particulate has formed a grey deposit that prevents their correct interpretation. The distribution and build-up of particulate matter in the courtyard varies in relation to the orientation of the elevation, but also by the type of exposure. The massive presence of calcium sulphate on the surfaces of the courtyard indicates that the degradation processes are to be linked mainly to the sulfation of the material. The loss of the mechanical properties of the mortars results. The presence of humidity and rain, acting both as solvents and as a vehicle for pollutants, worsens the problem. The analyses carried out on the mortars of the ashlar showed high humidity in the first superficial layers. These are materials that tend to favour the internal accumulation of water, which then tends to evaporate, triggering a series of highly stressful processes. This has led to a variation in the chemical-physical characteristics of the mortars now subject to disintegration phenomena.

4. The Project Before dealing with the theme of the conservation project, it is necessary to consider the overall objective of the programme proposed by the person responsible for the conservation of the Palazzo Ducale. The information collected had to be filed and organized in order to be immediately available in case of need. This type of request has led to the preparation of a HBIM model (which will be discussed in the next section) characterized by various levels of detail. In other words, based on the type of information, three types of models (general, architectural and detailed) have been processed. For general data concerning modern or historical cartographies, the general bibliography refers to a simplified model with geometric definitions. The data derived from the archival documents, in particular the restorations, have been linked to a model that incorporates the detail of the technological elements. The project presented here was first reported in an Autocad representation (it should be remembered that the work in HBIM is still in the experimental phase and, to comply with the regulations in force, a project with traditional representations was also carried out), then revised in HBIM mode. This double representation allowed us to grasp the actual potential of the HBIM model, especially in the organizational aspects, for future management of preventive and programmed conservation. In light of the different characteristics of the elevations (as highlighted above), we have tried to organize the project work, giving value to the differences found (Figure 13). Based on the results of the investigations illustrated, interventions described both in tables and in specific sheets with all the operational phases were identified. Heritage 2019, 2 1455 Heritage 2019, 2 FOR PEER REVIEW 16

Figure 13. ThematicThematic analysis analysis of the the project project (on the the top, top, a a material material survey; survey; on the the bottom, bottom, a degradation degradation survey.

5. TheThe H-BIM overall Model objective Setup of the operations is to guarantee the conservation of the original materials, when identified, and of the additions, even those of a relatively recent age. As described in previous sections, the operations conducted to study the fronts of the The second objective clashes with the canonical conservative approach, which sees cement Cavallerizza courtyard were numerous and varied; they included archival research, geometrical integrations as things that must be demolished and replaced. The study of the restoration interventions, qualitative survey, appraisals, on-site analysis and observations, which together led to choosing the starting from the early 1900s, clarified how the use of cement has been a common practice in different best practices for the conservation project. Those actions are all part of a team effort that has never, forms, such as mixed mortar or cement mortar. These changes in materials have mainly affected the in the history of the courtyard, been so comprehensive: loss or poor management of this content would be a major setback for all the professionals involved in its care.

Heritage 2019, 2 1456 lower portions, while the upper ones still preserve the ancient materials. Since numerous cement integrations are present (and are of good moulding technique, not approximate repairs), it has been decided to preserve them. Naturally, these choices make it necessary to relate them to the lime mortar elements and, above all, to limit their degradation by water. Another criterion for evaluating the interventions is the typology of actions carried out in the recent past, of which we have evidence from project appraisals. Within these, it emerged that numerous resins and surface consolidatives have been used since the 1980s, implementing water damage. Given the importance of the physical matter treated, the project used the materials as the guiding line for the interventions. Therefore, they are differentiated according to the type of material subjected to certain degradations. The identification of materials and degradation has, for now, been carried out directly. There may be additions to the definitions and to the type of problems during the construction site, when the choices will not only be conservative but also for the finishing. The project for the surfaces has supported the choice of operating according to the different fronts, which guarantees a respectful attitude towards the different construction phases of the courtyard. This choice has made it necessary to introduce the use of numerous different types of plaster (rusticated or smooth) to which, in many cases, the intervention takes on a similar character while keeping a different material appearance. The guiding criteria also foresee a dry cleaning phase: we want to avoid introducing water, even with nebulization, because the environmental humidity is already too dangerous to exacerbate it with prolonged watering, which would cause the salts to reactivate. The only actions to be carried out with water will involve sponges being soaked and then immediately squeezed out (so as not to cause drips) or the execution of compresses, at controlled levels of humidity. Dry cleaning will be carried out according to tradition and with ordinary equipment. The cleaning operations aim at reducing the presence of salts and, in particular, of sulphates on the surfaces. Cement mortars, which appear de-cohesive and/or detached from the wall supports, will be removed, such as the synthetic polychromy applied during previous restorations. We plan to integrate the gaps and to fill in the damage to the wall structure and to the external coating with mortar of good mechanical strength, permeability and breathability. The mortar, in addition to performing a protective action, must be formulated to have adequate texture and colour (to match the surrounding surfaces in an organic way). The integration must be carried out to be compatible with the original from a physical and chemical point of view. The mortar will be characterized by high porosity, which allows for the reduction of water accumulation by acting, at the same time, as a expendable material in case of continuous degradation. The colour must be chosen by functional and aesthetic criteria, similar to that of the material to be preserved. In case of the fragility of the binder that constitutes the rusticated plaster, it must be consolidated using inorganic materials, which can also be used for the possible adhesion of the polychrome layers to be preserved.

5. The H-BIM Model Setup As described in previous sections, the operations conducted to study the fronts of the Cavallerizza courtyard were numerous and varied; they included archival research, geometrical qualitative survey, appraisals, on-site analysis and observations, which together led to choosing the best practices for the conservation project. Those actions are all part of a team effort that has never, in the history of the courtyard, been so comprehensive: loss or poor management of this content would be a major setback for all the professionals involved in its care. A (relatively) new way to avoid this is Building Information Modelling practices: these drafting tools allow us to combine information and geometry in the same parametric modelling environment, which becomes a single container for all of the building’s data. The Cavallerizza case is a valuable heritage building, hence the capital “h” before BIM. This branch of the subject is dedicated to drafting models that adhere as much as possible to the existing assets, Heritage 2019, 2 1457 a difficult task: parametric modelling uses standard, rigid tools not suited to the complexity and diversity of historic buildings. The information then added to the virtual geometry of the building (an especially historically rich one) creates a proper database within the software, which can contain all information related to the past and, perhaps, the future care (in terms of programmes and actions) of the building. In this case, an experiment with this technology has been carried out on a sample of the southern façade. One of the spans of the Rustica front was set up in a possible BIM layout. This is a simplified version of the geometry, given the fact that overall functioning had more importance than geometrical precision. However, it was drafted according to the laser scanner point cloud (product of the survey campaign) and therefore metrically correct, although simplified. The application used for modelling was Autodesk Revit, and the cloud was imported thanks to Autodesk Recap. The main challenge, for the front of the Cavallerizza, is the varied superficial decorations that give the site its unique image. As described in the materials section (Figure 13 on the top), each element is different and has different conservation needs, so for each of them it is necessary to link different information. This feature immediately highlights some problems specifically related to HBIM and Cultural Heritage [10]. On the one hand is the need to not lose the metric accuracy that can be achieved in the survey phase: modern BIM authoring software still does not allow one to manage all the irregularities of the built heritage and therefore forces important choices related to the accuracy of the final model (Adami). The BIM modelling environments also dialogue with a finite number of technological elements; these often do not include historical elements and many types of decoration. In this case, tricks must be found to adapt the software tools (designed for new constructions)—the families in the case of Autodesk Revit—to the existing heritage. The major problem is the ashlars. Typologies and shapes vary throughout the fronts and the levels and materials vary relative to the different interventions. The average span contains more than 60 ashlars; managing them separately would create a huge number of free-standing elements in the same environment. Therefore, the decision was made to first create a curtain wall item for the whole rusticated portion of the main floor of the building. The quality of this element in the software is to have a container of panelling systems constituting a curtain wall. If in place of a panel, the mortar ashlar becomes the recurring element, so can describe this decoration effectively (the depth and shape of the ashlars can still be assigned singly). This works smoothly on the portion of the main floor; less so on the ground floor, where the ashlars are much more irregular. In this case, the decision was made to accept this difficulty in modelling, with precision, all the elements of the architecture: this allows us, instead, to obtain an efficient representation of the other intended uses of the HBIM. Indeed, the strength of this system, and the core of the experiment, is linking different sources to one item, which was carried on despite difficulties. The example shown in Figure 14 illustrates the three-dimensional object, the scheme for the different elements positioned on the surface of the main floor (approximately the material classification analysis) and the string-course frame. One of the quadrangular panels shows the power of this tool: information on the material and the damage (from two different sources) appear together in the description of the element. The possibility of linking analyses and observations of various types (texts, photographs and drawings) to the elements of the BIM model, as shown in the example, is an important advance in the management of a restoration site: for the survey and analysis phase initially, but also later in the design and management of the architecture. Although it is not yet possible to fully exploit the potential of the BIM systems in the context of interventions in the existing heritage, this first step allows us to build new relationships: between the analysis and the object and between different types of analysis. This also leads to a greater integration of the team of researchers and professionals who Heritage 2019, 2 1458 intervene, each in its own field of expertise, in the restoration process, but who are often unable to make a comparison with each other. Finally, the structure of the HBIM system is also suitable for monitoring the restoration site, allowing the precise recording of all the operations carried out and the attribution of the interventions to the various operators: it therefore becomes a sort of digital “site register”, which, however, is not a separateHeritage 2019 document,, 2 FOR PEER but REVIEW is directly integrated with all the other data present in the system. 18

FigureFigure 14. 14.Example Example ofof aa generalgeneral sectionsection of the CavallerizzaCavallerizza façade façade with with the the scheme scheme for for the the different different elementselements positioned positioned on on the the surface surface of the of mainthe main floor (approximatelyfloor (approximately the material the material classification classification analysis) andanalysis) of the and string-course of the string-course frame. frame.

6. ConclusionsThe possibility of linking analyses and observations of various types (texts, photographs and drawings)The article to the summarizes elements of the the project BIM model, path activated as shown for in the the conservation example, is an intervention important advance at the courtyard in the management of a restoration site: for the survey and analysis phase initially, but also later in the of the Cavallerizza in Palazzo Ducale in Mantua. design and management of the architecture. Although it is not yet possible to fully exploit the As it emerges from the writing, the close collaboration between the Palazzo Ducale and the potential of the BIM systems in the context of interventions in the existing heritage, this first step research institutions (Politecnico di Mantova and Centro Conservazione e Restauro Venaria Reale) has allows us to build new relationships: between the analysis and the object and between different types led to good results in every preparatory phase of the project. of analysis. This also leads to a greater integration of the team of researchers and professionals who Each body has addressed the problems expressed about the historical artefact, proposing and intervene, each in its own field of expertise, in the restoration process, but who are often unable to comparing possible conservative solutions as represented in the ﬁnal plan, which is now in the contract make a comparison with each other. phase. Contrary to what can be assumed, the Courtyard of Cavallerizza has undergone sporadic Finally, the structure of the HBIM system is also suitable for monitoring the restoration site, interventionsallowing the inprecise recent recording years and of theall the memory operations of these carried operations out and hasthe attribution been lost. of the interventions to theOnly various a few operators: archival documents it therefore testify becomes to thea sort operations of digital carried “site register,” out, and which, mostly however, without graphicis not localization.a separate document, The lack but of physical is directly conﬁrmation integrated with of the all the operations other data carried present out in inthe the system. past has made

6. Conclusions The article summarizes the project path activated for the conservation intervention at the courtyard of the Cavallerizza in Palazzo Ducale in Mantua.

Heritage 2019, 2 1459 it necessary to carry out an investigation into the constituent materials of the decorative apparatus and the restorative materials. These investigations were also speciﬁcally aimed at identifying the technological and material diﬀerences made by Giulio Romano compared to the other architects who had worked on the construction. The large amount of data has stimulated the development of a HBIM model, both to collect information from documentary research from the new surveys and to set up a programme for the management of projects.

Author Contributions: B.S. had responsibility for the historic research; A.A., L.F., O.R. for the survey; B.S. for the analysis of materials and state of conservation; B.S., A.M., D.L. for the project; A.A., B.S., O.R. for the BIM application. Funding: This research was developed in the field connected to BIM (paragraph 5) within the project “Building Information Modelling for the planned conservation of Cultural Heritage: even a Geomatic question” (identification code RBSI144B5K) funded by the Ministero dell”Istruzione, dell”Università e della Ricerca in the national research framework SIR (Scientific Independence of young Researchers), 2014. Acknowledgments: This project was made possible thanks to the collaboration of the Centro Conservazione e Restauro “La Venaria Reale” and especially the director of the Scientific laboratories Lorenzo Appolonia. A special thanks to PhD arch. Nazarena Bruno for the development of the database connected to the BIM application, which started as part of her PhD thesis. Conflicts of Interest: The authors declare no conflict of interest.

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