Evaluation of silicone based products used in the past as today for the consolidation of Venetian monumental stone surfaces

The commercial consolidating siloxane compounds EAS 40, Rhodorsil Consolidante RC90 and RC80, and the silicone water repellent agents Rhodorsil H224 and Hydrophase were carefully applied to stone specimens and tested to ascertain their chemical nature and their stability under oxidative stress and degradative environments. The resins were applied to laboratory samples (Carrara marble and Vicenza white limestone specimens) and subjected to controlled natural weathering and artificial ageing. The film morphology and the penetration depth was observed and measured by SEM-EDS determinations, while the stability of the resins was monitored by FTIR, SEM-EDX, colorimetric measurements and sponge tests. The results were compared with those obtained from a spread sampling of Venetian surfaces treated in the second half of the XX c. with Sogesil XR893 and X54-802, silicone resins which are no longer on the market. The overall results prompted a number of considerations on the effects of the resins applied to stone materials and offered the authors the opportunity to make a practical contribution to current practices in the consolidation of stone materials

The (Building) Stones of Venice under Threat: A Study about Their Deterioration between Climate Change and Land Subsidence

Cultural heritage assets face significant threats from climate change and land subsidence, leading to extensive social, economic, and environmental losses, and damage to artistic and monumental heritage in Italian coastal cities. In particular, addressing these challenges in the Venetian context necessitates the development of an adaptation plan for the lagoon area and the identificat on of targeted intervention strategies to preserve cultural and territorial heritage. To address these objectives, a systematic study was conducted to investigate the deterioration patterns exhibited by the most representative lithologies used in Venetian buildings. Thirty samples of five carbonate stone varieties subjected to natural aging were monitored in six different areas of Venice’s historic center and on Torcello Island, selected based on altimetry relative to tidal zero and exposure to environmental forces. An integrated multi-analytical approach was employed to identify and map macro- and micro-morphologies of stone surfaces related to chemical weathering and physical decay. Stones underwent evaluation during nine monitoring periods using various tests (ultrasound P-wave velocity and colorimetric measures) and analyses (μX-Ray Fluorescence, X-ray powder diffraction, stereomicroscope observations, and recognition of biological patinas). Data processing aimed to elucidate how microclimate and intrinsic stone features influence the occurrence and progression of deterioration phenomena. From the experimental findings, a Stone Deterioration Index and Intervention Procedures (SDIi) were proposed to estimate deterioration rates and assess the need for targeted intervention through conservative actions

Original or post-war paintings? The fixed wooden scenery of the Teatro Olimpico in Vicenza: a guided multidisciplinary approach based on scientific analyses and HBIM

Archival resources, a photogrammetric survey, analysis of materials and techniques, and evaluation of the state of conservation were interconnected phases in the interdisciplinary research on the perspective scenery of the Teatro Olimpico in Vicenza. To fill existing gaps related to the history of this unique artefact and to the undocumented retouching of paint layers on the scenery during post-war reconstruction work, a broad analytical approach (optical microscopy, XRPD, SEM–EDX, μFTIR and μRaman) was applied to micro-samples, the selection of which was guided by consolidated geometrical and archival data. The aims were to obtain a characterisation of the pigments and binders and to evaluate the microstratigraphic sequence, the state of conservation of the scenery flats, and the deterioration processes involved. The findings unveiled a discernible variability in the production techniques of the finishes, frequently lacking the classic microstratigraphic sequence associated with the traditional method for painting on wooden panels from the sixteenth century. Moreover, by identifying many pigments that could be used as temporal markers we were able unequivocally to establish, for the first time, that a significant part of the scenery designed by the architect Vincenzo Scamozzi was heavily repainted in the post-WWII period. These analytical results and all the data collected on the artefacts over time were related through an HBIM model, enabling the historical and technical- analytical information to be linked to the geometrical survey and thus to provide guidance for actions based on current and future knowledge for the maintenance and monitoring of the Teatro Olimpico

Characterization of Barium Hydroxide Used as Consolidating Agent for Monumental Surfaces in Venice

Barium hydroxide was one of the most widely used inorganic materials to consolidate calcareous stones during the 19th and 20th. The consolidation process occurs through a carbonation reaction. Several researchers studied the consolidation mechanism; however, the results are sometimes in conflict. More experimental work using modern analytical techniques and a multi-analytical approach is necessary to shed light on the mechanisms involved. This research aims to validate the chemical composition of the developed secondary products and to evaluate the treatment’s effectiveness over time. Carrara marble and Vicenza white limestone were treated and subjected to natural, artificial, and biological weathering. Furthermore, only a few microsamples were collected from Venetian historical artifacts treated in the 1960s and 1970s. Microscopic observations, sponge tests, FTIR, SEM-EDX, and microbiological analyses investigated the stability of the treatment over time and ascertained the chemical composition of the acicular crystals developed from the carbonation reaction of barium hydroxide. The results prompted a number of considerations useful for future restorations and for developing innovative compounds for consolidation interventions

Characterization of Barium Hydroxide Used as Consolidating Agent for Monumental Surfaces in Venice

Barium hydroxide was one of the most widely used inorganic materials to consolidate calcareous stones during the 19th and 20th. The consolidation process occurs through a carbonation reaction. Several researchers studied the consolidation mechanism; however, the results are sometimes in conflict. More experimental work using modern analytical techniques and a multi-analytical approach is necessary to shed light on the mechanisms involved. This research aims to validate the chemical composition of the developed secondary products and to evaluate the treatment’s effectiveness over time. Carrara marble and Vicenza white limestone were treated and subjected to natural, artificial, and biological weathering. Furthermore, only a few microsamples were collected from Venetian historical artifacts treated in the 1960s and 1970s. Microscopic observations, sponge tests, FTIR, SEM-EDX, and microbiological analyses investigated the stability of the treatment over time and ascertained the chemical composition of the acicular crystals developed from the carbonation reaction of barium hydroxide. The results prompted a number of considerations useful for future restorations and for developing innovative compounds for consolidation interventions

Study of the deterioration products, gilding, and polychromy of the stones of the Scuola Grande Di San Marco's façade in Venice

The Scuola Grande di San Marco is one of the most outstanding Renaissance buildings in Venice. Destroyed by fire in 1485, the Scuola was reconstructed between 1487 and 1495 by Pietro Lombardi (and sons), together with Giovanni Buora and Mauro Codussi. The façade is considered one of the finest and most original exteriors of Venetian buildings and in particular features refined sculptural and painted decorations and a remarkable pictorial effect created by the extensive use of polychrome marbles and the false perspective view between the pilasters of the lower order. Most of the stone materials (Istrian and Verona red limestones, nero di Roveré, pavonazzetto toscano, Carrara marble and various reused antique marbles) present evident decay phenomena such as scaling, exfoliation, powdering, fissuring, salt efflorescence, black crusts, and artificial patinas of various kinds. The present study reports the results of petrographic and chemical laboratory analyses carried out in preparation for the conservation treatment of the building, in order to characterize the main micro- and macro-morphologies of decay and to identify the causes and mechanisms of deterioration as well as the nature and application technique of the polychromy, gilding, and patinas present on parts of the monumental Renaissance façade

Caratterizzazione chimico-fisica di mattoni gotici veneziani

The aim of this experimental work was determine the characteristic features of Venetian Gothic bricks, in order to create an initial database for the city of Venice, and improve our knowledge of this class of materials, for the conservation of the walls of Gothic buildings and the dating of architectural surfaces. The study was extended to bricks found in dated archaeological sites of the town and of the Venetian lagoon. A total of 34 samples was subjected to mineralogical-petrographic, chemical and physical analysis (oM, XRD, SEM + EDS, XRF, MI) to get a initial overview about these Venetian bricks. The results identified some groups of samples sharing the same source materials and, probabily, also the same manufacturing technology. The study showed that this grouping does not depend on the origin of the bricks, rather on their dating, as di-mostrated by comparison with data related to more ancient Venetian bricks