The Lapidary of Palazzo Ancarano. Digital technologies and 3D printing to improve knowledge of the stele collection

Palazzo Ancarano is currently the main office of the Archaeological Superintendence of Emilia Romagna. It is located in the ancient Via Belle Arti, in the historical center of Bologna, just a few minutes away from some of the most important monuments in the inner city, such as the Two Towers and the Basilica of San Petronio. There is a courtyard inside the building with an entrance that leads to the offices of the Superintendence, which houses a modest collection of steles. After five years of logistical planning and studies on stone restoration involving the stele collection in the courtyard of the palace, the Lapidary of Palazzo Ancarano was recreated through the recent collaboration between the Academy of Fine Arts and the Superintendence. The work presented here concerns a project proposal for the re-evaluation of the courtyard with the goal of bringing it back to its original function as exhibition path. This can be achieved by combining the study of the objects and contemporary technologies. Thanks to the data gathered, the artifacts will be available to a wide range of people through an application that shows the virtual reproduction of the ancient objects. This app will also contain all the information about the restoration work of each student of the Academy of Fine Arts. Outdoor installations in the courtyard with interactive 3D printed models are under consideration as well.

Figure 1. Aerial view of the area and identification of the palace.

The palace is named after its founder Pietro d'Ancarano, a renowned citizen and teacher of canon law in Bologna and other Italian cities during the fifteenth century. Pietro d'Ancarano descended from a branch of the Farnese family established in Tuscia, as he declares in one of his most the famous works, the "Sextum": "Ego Petrus de Ancharano de Nobilibus de Farnesio Provinciae Patrimonii Beati Petri in Tuscia." His biography is known from his writings and letters sent to family members and colleagues, in which there are found details about his life. In a letter dated August 1381 and sent to Michele Migliorati da Prato (the vicar of the city of Rimini), he notes that he is a 'doctor utriusque iuris.' In another letter, dated between 1382 and 1384, his temporary return in Bologna to avoid inactivity and misery is evidenced by his words: "sumpto gradu utriusque iuris, veni Bononiam pro vicario domini potestatis." Thanks to his new position, his career took off and he became the Repubblica's consultor in Venice. He taught in various Italian universities from 1387 to 1395, the year of his final return to Bologna and to the oldest university in the world, at that time known as "Studio Bolognese." In this last period of his life, Pietro was Viceregent of the Archdeacon, but in October 1412 the canons of St. Peter's Basilica created the 'scandalum maximum' in the Studio (Liber Secretus 1938, 197-99) because they claimed the right to exercise the Archdeacon's functions in case of Pietro's absence. It seems that this conflict was also a consequence of the political position taken by Pietro d'Ancarano and other jurists concerning the intricate events of the Great Western Schism in 1405. In fact, his objective was the reestablishment of unity. He dedicated his life to teaching and to an active participation in debates on societal issues, so as to encourage young scholars from other cities to come to Bologna to study. Through his will, he set up a boarding school in his home for poor students. Pietro d'Ancarano died in Bologna on 5 August 1415 and was buried in the Basilica of San Domenico. This institution, known by the name of Ancarano, was located in the residence of the founder in Via Val d'Aposa for more than a century. But in 1532, the whole college was transferred to Borgo della Paglia, in the district of Porta Piera, today called Via Belle Arti.

By the XVIIth century, the palace was embedded in a complex of buildings built specifically to house Jesuit novitiates. Two centuries after its foundation, the college was moved and in 1780 it was abandoned; the Jesuit Order had been abolished in 1773. Palazzo Ancarano remained empty until 1804, when its premises were granted to the new National Academy of Fine Arts, formerly Clementine Academy, where it is still today. In 1925, the Academy of Fine Arts gave some rooms to the Royal Superintendence of Antiquities of Emilia Romagna. The Lapidary in the inner courtyard of the palace was begun at this time.

Since then, the courtyard has contained some funerary monuments discovered during archaeological excavations as well as during construction work in Bologna's historic downtown and its surroundings. The archaeological collection consists mainly of Roman funerary stones and other objects made of various materials, such as Varignana yellow sandstone, and a unique monumental column section in selenite; these are both local materials. The collection also includes imported ancient marbles and limestones, which come from the most remote locations of the Mediterranean basin. The preserved inscriptions are from different historical periods: some of these are pre-Roman memorial stones; some finds come from the period between the late Republic and early Empire (end of 1st century BC - 1st century AD); and other finds are from the Medieval and Renaissance periods. Among the items in the collection is a medieval tombstone dated to the late 14th or early 15th century, in Istrian stone, discussed below in section 4. The pieces can be divided in two main groups according to their time of arrival in the courtyard. An initial nucleus of steles was discovered during excavations in the 1930s in the following municipal locations: Due Madonne, Santa Viola, Battiferro, and Ponte Lungo. A second group came during the 1960s from excavations in these communal locations: Bitone, Arcoveggio, San Donnino and San Donato. It is interesting to note that the discoveries were made almost outside of historic city center. This is due to the fact that at the time of Roman city of Bononia, burials were located only in proximity to the main roads that led out of the city. Since the early years of acquisition, all the pieces have received sporadic restoration interventions, but these were not enough for their conservation. Subsequently, the courtyard arches were buffered in order to get more room for display the objects, and gradually some pieces of the first group were placed along the exterior walls because there was already the idea of creating an exhibition space. The remaining space was subsequently occupied by finds found after the first arrangement. They were organized by following a criterion of similarity of form and size, or of epigraphic character and the arrangement of the written text. Despite this intent, the directive to create an exhibition space was soon abandoned. The gradual accumulation of finds has thus caused the transformation of the yard into an open-air warehouse.

In 2012, the idea of creating an exhibition path was proposed again and the restoration project of the Lapidary begun. It was the first project promoted by the Restoration Course of the Academy of Fine Arts of Bologna (ABABO) in cooperation with the Superintendence of Cultural Heritage of Emilia Romagna. This partnership was also the result of the proximity of their offices. Indeed, the two institutions are in the same block. It was also created to pursue common interests, such as the need for students to apply theoretical studies in the field and the need for the Superintendence to restore archaeological finds in the field. The project of changing the intended use of the courtyard was reconsidered. The restoration phase was carried out by thirty-one students guided by four professors, following a precise schedule. Students involved were those belonging to the second and fourth years (from the years 2012 to 2016) of the academic course of restoration of stone materials; during this time they implemented a practical testing laboratory, working on real archaeological finds to increase their abilities. Thus, the collaboration allowed us to open an important restoration site and to focus on the Lapidary located in the courtyard of the historical Palazzo Ancarano. The initial project was for a period of three academic years; another year was added for the repositioning of the finds in a logical and chronological path along the façades of the inner courtyard. The maintenance of an archaeological find was assigned to each individual student, with the purpose of producing a complete documentation of the intervention, using an inventory document specifically designed and produced under the supervision of the responsible professor, Augusto Giuffredi. This document includes all necessary information about the archaeological remains and operations performed; the problems of degradation and their mapping; and the materials used for the restoration in the different phases. The result of the work done in the restoration yard is an archive containing 54 inventory documents, each one of which concerns a single archaeological find. This archive was made to preserve of all the archaeological artifacts, in this way leaving a testimony of the work done for those who will have to do further restoration work in the future.

Figure 2. Phases of the restoration yard.

The restoration yard work was divided into three phases. More specifically, the first phase included documenting the discovery of the archaeological find and the gathering of all the existing information about it, including, for example, the location where the piece was discovered in the territory of Bologna, and the document in which it was transferred to the palace courtyard. In this phase, there was also the cognitive analysis of the find, which was based on the observation of its state of preservation; the analysis of the size and weight of each possible fragment; the photographic documentation; the historic technical execution; the material analysis; the in-depth analysis on the decay and the possible causes for it; and, lastly, a graphic mapping for each type of decay.

In the second phase, the stone restoration operations on the artifacts were carried out; this was the most challenging part of the program because it required the students to draw up a specific intervention project for conserving the manufactured article assigned to them. In most cases, the project provided multiple phases of intervention, such as the removal of non-adhering deposits; the preliminary cleaning tests and selection of the most suitable cleaning agent(s); the removal of adhering deposits with compresses; the cleaning with sponges and toothbrushes; and the bonding of possible fragments with resins.

At the final stage of the restoration yard work, each artifact was moved from the place where the restorations were done to the inner courtyard of Palazzo Ancarano and placed in the proper chronological order, situated in the arcades and enhanced with special methods projected ad hoc.

Figure 3. Restoration phases concerning the medieval tombstone codified as V7 (left to right): removalof non-adhering deposits; epigraph frottage; removalof adhering deposits withbiocidal and Arbocel compresses.

Figure 4. Restoration phases concerning the medieval tombstone codified as V7 (left to right): cleaning with sponges; bonding of fragments with bicomponent epoxy resin; bonding in vertical position with security straps.

Figure 5.Restoration phases concerning the medieval tombstone codified as V7 (left to right):moving the tombstone into theestablished location on the east façade; control of the resin spillage along the fractures; cleaning of the epoxy resin with ethyl alcohol.

The project proposal concerns the re-evaluation of the collection of steles and the palace's courtyard, thus completing the exposition that was planned for it in the second half of the twenties and for which reason it was filled with archeological finds. When the students had completed their stone restorations and the yard was closed, the idea of the project was born. This work was the last stage of the master's degree thesis in stone restoration written by Veronica Villa at the Bologna's Academy of Fine Arts. She was one of the thirty-one students who had joined the project and, in particular, she was assigned to carry out the restoration of the medieval tombstone of Istria stone, codified in the stele system of the Lapidary as V7. To restore the original function of the courtyard it would be necessary to open it to the public and make an expositive path that would be of interest to a wide range of visitors. The best way to do this would be to install durable outdoor technologies that can share contents with the visitors' devices in an interactive way. The project proposal was developed thanks to the collaboration with students of the Architectural Department at Florence University. The students from Florence had already worked on this kind of interactive exposition and they completed the survey of the courtyard and the archaeological remains. They also developed the project proposal in accordance with the requirements. The approach used for the retrieval of metric data was the photogrammetric survey, chosen because this technique is able to obtain a three-dimensional high-quality product without compromising the measurements' accuracy and reliability.

Figure 6. Main workflow of the restoration phases and surveys in the Lapidary of Palazzo Ancarano.

The survey began in July 2016 after obtaining the necessary authorization by the Archaeological Superintendence of Emilia Romagna in order to have access to the courtyard and to collect photographic data. The was necessary because archaeological remains are protected by Italian law, specifically the "Decreto legislativo 22 gennaio 2004 - n°42 - Codice dei beni culturali e del paesaggio." This law states that all assets owned by the Italian State that are of artistic, historical and archaeological interest are entrusted to the Territorial Superintendences. The objects that are not exhibited in museums are collected in deposits owned by the State and they are accessible only after obtaining permits. In the case of Palazzo Ancarano, the Academy of Fine Arts reached an agreement with the Superintendence to restore and make accessible to the general public through article 119 of Legislative Degree No 42/2004, 'Dissemination of knowledge of Cultural Heritage.' It lays down the guidelines of the agreements between the Ministry of Education and the University. The survey was divided into several stages. First of all, we decided to undertake a preventive inspection of the area to assess the state of preservation of the objects and to determine the best times for gathering photographic data. The photographic survey was the second part of the work and was done with a digital camera, the Nikon D3200 with 24 Megapixel and with the Nikkor 18-55 mm lens. It was necessary to use a tripod in order to avoid micromoving problems during the acquisition of the photogram. The shots were made by the camera set in aperture-priority auto mode, in which the D3200 automatically selects the shutter speed that will produce the optimal exposure while allowing users their choice of apertures. We used it with small apertures (high f-numbers) to increase the depth of field and to bring out details in the background and foreground. The third phase was the direct measurement with the laser measuring instruments and manual tools. The photographic acquisition did not foresee the use of flat targets, because the geometrical characteristics of the tombstones and the courtyard acted as reference points for the correct alignment of the photos and the subsequent building of a sparse cloud. Finding the best shooting position was particularly difficult, due to the small dimensions of the Palace's internal courtyard; this made it impossible to collect all the photo data necessary for the correct rebuilding of the facades up to their tops. To solve this problem, we have requested some additional permissions so as to have access to the first floor of the building, where there are the administrative offices of the Archaeological Superintendence, and to create four shooting positions from the windows of these rooms, framing the opposite facade's top.

Figure 7. Main stages of the Agisoft Photoscan process concerning V7.

Regarding the survey of the collection's pieces, we located a specific shooting position for each find. At the end of the photographic survey, there was the final phase, which included the processing of data collected through the use of the Agisoft PhotoScan software. This was very intense processing and it included the following: the identification of target areas in the photo; the alignment of these and the generation of the sparse cloud necessary for the subsequent creation of the dense cloud; the building mesh and process occlusion of the holes; and the creation of textures. The product output from this processing was a PhotoScan mesh too large to be displayed easily by the final users. For this reason, the mesh was simplified to enable faster viewing that is a necessary adjustment to be exploited by portable devices like smartphones or tablets. The 3D models obtained by such data processing pertained the courtyard as an architectonical element and in a more detailed way each archaeological find so that we have different kinds of processing for the expositive path project. These have been organized in a way that enables them to be included in the proposal for the integrative method that involves the use of digital technologies. For informing people about the palace, such integration between the archaeologic patrimony and the innovative technologies is necessary, so that all visitors, from children to scholars, can benefit from our work.

From the three-dimensional model of the courtyard it was also necessary to extract a bi-dimensional survey of it, with which we have been able to design the exhibition path and to position the cognitive panels. These panels present the best outdoor permanent solution capable of grouping the interactive elements concerning each archaeological find.

The first graphical elaborations that were extrapolated were the prospects and the zenithal views of the complex actual state. This was necessary because the existing bi-dimensional graphic elaborations of the building have a very low-grade detail and they have not been updated with the actual condition of the courtyard after the restoration work and the rearrangement of the restored steles along the façades.

The Lapidary's access is located next to a "corridor" in the south façade. The particularity of the courtyard is that it has got the eyesight of the Archaeological Superintendence, but also the eyesight of some schoolrooms owned by the Academy of Fine Arts. The style of the façades is coherent, although the restoration work done on them has characterized the elevations in different ways. Excluding the roof structure, the façades have a height of approximately ten meters, with a variability of ten centimeters due to the slope of the flooring, probably owing to the original instability of the stamping plan on which it is installed. The only staircase that leads to the underground area where the Superintendence's warehouse is located is in the corner of the East front.

Figure 8. Vector drawings of front elevations.

Both the first and the second row of arches were bricked up in the early XXth century in order to create indoor rooms. Two windows in the second row of columns on the west front were also bricked up. On the south elevation, the windows on the second floor cover the whole area between the arcades, presenting a different choice for the architectonic restoration of the façade. The arcades were also bricked up; they have a frieze composed of terracotta tiles on which there are little angel faces with wings. The repetition of the frieze reveals a serial production of the tiles using the same matrix. The capitals are made in a composite style with sandstone, differing from one another in the varying forms of acanthus leaves decorating them. The columns under the capitals are of brick; they rest on a molded sandstone base. On all the façades, there is the same string course frame. During the final phase of the work in the restoration yard, the arcades of each façade were numbered to allow a more precise placement of the objects. Despite the fact that the east front does not have arcades on the ground floor, the tombstones were placed with the same spacing that was used for the other façades.

Figure 9. Orthophotos of front elevations.

Through a dimensional analysis of the spaces, we have identified the most appropriate points for the positioning of the panels, which form a path running along the entire perimeter of the courtyard. In the axonometric view, we have inserted the panel construction hypotheses, in which there are fourteen cognitive panels, some placed individually and others arranged in pairs, depending on the need. There are fifty-four archaeological artifacts arranged in the panels, based on their position in the courtyard.

The cognitive panels form a support element that encloses various technologies in order to meet the needs of all visitors. Information about the objects is printed on a transparent base, so that the visitors can remain linked to the context without any distraction. The panels are different from each other, but they share the same layout of their upper level, on which there is a complete and detailed disclosure about the codes of the pieces positioned on the façade; in front of each panel vector drawings demonstrate the positioning. On these, only the objects inside the panel will be colored. On each panel, there is a detailed description about the object, its history, and its conservation treatment, along with a lot of other helpful information written in Italian, English and Braille. In the prototype, which is dedicated to the medieval tombstone codified as V7, we have developed all the technologies that we have proposed. These will be used only on the more historically interesting objects. Another of our goals is to create an exposition path designed for blind and visually impaired people. For this reason, we have used an embossed plate written in braille, and the graphical illustrations are in relief. In fact, the panels are characterized by a very flat surface so that there will not be any misunderstanding about the panels' functional design. In the central part of the panels there are three-dimensional physical models printed in plastic material, which is useful for understanding all the fragmentary remains that were reassembled during the restoration.

Figure 10. Axonometric view of exhibition path and detail of the prototype panel about V7.

On the V7 panel, the model is presented as a new learning system for children, who can reassemble the medieval tombstone directly on the panel using a system of magnets. This model is also designed for blind and visually impaired people, who can immediately and completely understand the remains using their tactile sense, thanks to the small dimensions of the model. In the lower part of the prototype panel there is a wireframe reconstruction of the original item, which highlights some details of the object that are barely visible to the naked eye. Specifically, this is accompanied by a particular deepening of the epigraph on the medieval tombstone V7 and its probable translation. On all panels two QR codes will be positioned and visitors will be able to read the details of all the artifacts from the dedicated exposition app, with their smart devices simply framing the codes. These are certainly not new technologies, but their combination may be the right solution to increase peoples' interest in and understanding of the archeological patrimony of the Lapidary.

The specific survey of every single tombstone was made in order to have a work of impressive quality so that we could get the best results during the making of digital 3D models of each artifact. These high-quality 3D models will have to be suitable for visitors' devices, which, due to their technical limitations, cannot open and manage the very complex files. As a result, these files will be converted into a light and simplified format with fewer details, but keeping high quality images. The big and complex files generated from the survey were used to enable the 3D printing process to be done using plastic material so as create 3D physical models, which are the main part of the alternative learning process about the artifacts, as mentioned above. The idea of creating a dedicated app for the Lapidary exposition was the result of an analysis made for understanding the potential of the path and the types of visitors that could be attracted by it. The main advantage of having an app of the Lapidary is to have the entire database of all the finds placed in the courtyard of Palazzo Ancarano on hand and available to all users. These finds are to be organized in a digital list, in which each one has a section with all the information about itself, constantly updated by the Lapidary's staff and by researchers. The users can select the artifact about which they want to know something more, and they can read about the technical specifications of the restoration, view the photos of the previous phases and see the inventory document of ABABO about the work on them. One of the more interesting functions could be the insertion of information about the phase before the restoration of each one of the remains. For example, such information could include the printed documentation digitalized and presented by the students who did the work on that tombstone; the photographical documentation about the state of the object before restoration in comparison to its present state; and of particular interest, details about the diagnostic phase of the causes of degradation and how this is linked to the subsequent restoration process. These features would be extremely useful, because in this way there could be a database that would be accessible from everywhere and by everyone, with a lot of high quality information and files, so that many professionals would be able to connect to this database and develop studies about the Lapidary.

In the app, there is also a link through which users can connect their devices to the collection of 3D digital models by Sketchfab, loaded into the database by the Lapidary's profile on this hub. Users can access it directly through the second QR codes on the panel. This solution was chosen because the visualization of 3D models on mobile devices is already a consolidated technique to give the user a complete understanding of an element. It is done with the younger generations as the target, because developers want to educate children and teenagers about the conservation of the archaeological patrimony using tools such as mobile devices that they know very well. Moreover, not only students, but also ordinary people and scholars as well, can learn many new and interesting things by engaging in game-playing or an interactive learning process, thus increasing the community's interest in the local archaeological and artistic patrimony.

Figure 11. Overview of the app's contents, an example of some information available about V7: graphical diagnostic of decay, photographic data and 3D digital model.

The method applied to Palazzo Ancarano's case is, at this time, only a project proposal, so it is not possible to get numerical data on the real usability of the site; however, it would allow the lapidary not to return to being just an open-air storage, regardless of the potential visitors. The increase in interest is only one of the purposes pursued by this method, and in fact the documentation produced would remain as a testimony available to the public, even if it changes its intended use. In addition, this method is also proposed as an example of re-evaluation for those places of historic and artistic importance which have been left to their own devices and which may not have the relevance that they should have.

The reorganization and redevelopment of the Palazzo Ancarano's Lapidary was one of the first restoration school yards sponsored by the Academy of Fine Arts in collaboration with the Superintendence of Archaeology, Fine Arts and Landscape for the metropolitan city of Bologna and the provinces of Modena, Reggio Emilia and Ferrara. In the four years of the construction of the site, several students were able to study the field of restoration of stone materials and increase their knowledge, acquiring a solid foundation in order to properly restore of works of greater importance in their later career. Through the restoration, each mobile artifact belonging to the stele collection recovered a correct reading inside the Lapidary. The museum function of the courtyard had been totally lost because of the state of abandonment of the works accumulated over the previous years, but now it has been gradually restored by designing an exhibition path based on the needs dictated by the present artifacts. The project proposal presented here promises to be the necessary catalyst to reverse the previous state of abandonment. This work began as an agreement between students and ended with the integration of their operations with technologies capable of attracting the public interest. This could be a method applicable in many national territories where there are sites that are currently abandoned because they are not considered relevant or due to lack of funds. Many of these have fallen into a state of deterioration and they need restoration interventions on artifacts to recover their cultural heritage, for the value of the archaeological site where they are and for the maintenance of its historical identity.

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