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

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

Archaeometric investigations of the materials and techniques of two red figured kraters by the Painter of Louvre K 240

Two very important red figured vases by the Painter of Louvre K 240 – the Acrobat krater preserved in the L. Bernabò-Brea Regional Archaeological Museum of Lipari (Sicily), and the Fleischman krater of the J. Paul Getty Villa (Malibu, Los Angeles) – were submitted to stylistic and archaeometric examination, the latter by powder-XRD, OM on thin sections, SEM + EDS on polished sections, and FTIR to characterise the component materials (ceramic body, black glosses, pigments and media) and the manufacturing technique. The results indicate an identical illitic, slightly calcareous clay used for the manufacture of both vases that were then painted with a very similar slip, then turned a gloss black by firing in a reducing atmosphere. The provenance of the clay could not be precisely determined so far. Both kraters were also painted with a very similar technique, so that it may be concluded that they were produced by the same artist in a unique atelier yet to be identified.Deux importants vases à figures rouges dus au peintre du Louvre K 240 ont fait l’objet d’un examen stylistique et archéométrique : le « cratère à l’acrobate » conservé au Museo archeologico regionale Luigi Bernabò-Brea de Lipari, en Sicile, et le « cratère Fleischman » aujourd’hui à la J. Paul Getty Villa à Malibu, Los Angeles. Pour l’examen archéométrique, on a utilisé la diffraction X sur poudre, la microscopie optique sur des lames minces, la microscopie à balayage électronique + la spectroscopie à dispersion d’énergie sur des coupes polies, et la spectroscopie infrarouge à transformée de Fourier pour déterminer les matériaux constitutifs (pâte céramique, vernis noir, pigments, liants) et la technique de fabrication. Les résultats révèlent qu’une argile illique légèrement calcaire identique a servi pour la confection des deux vases, enduits ensuite d’un engobe très semblable, transformé en vernis noir par une cuisson en atmosphère réductrice. La provenance de l’argile n’a pas pu être précisée pour l’instant. L'application des couleurs est similaire également sur les deux cratères, qui seraient donc l’œuvre d’un même artiste travaillant dans un atelier unique qu’il reste à identifier