ABSTRACT
Samples of orange patinas found on a limestone window tracery and an ornament of the Batalha Monastery have been investigated by X-ray micro-diffractometry (µ-XRD) and low-vacuum scanning electron microscopy coupled with energy dispersive spectrometry (LV-SEM + EDS). The aim of the study was to determine the composition of the layered patinas, assess whether they have been intentionally applied or naturally formed, and study their degradation patterns. Preliminary results revealed that the orange patinas on the window tracery and the ornament showed different compositions and appearance, suggesting distinct formation pathways. Orange patinas on the ornament, which are now showing decay and delamination patterns, mainly consisted of gypsum with hematite as a minor component, implying the possibility of an intentional application of a mixture of ochre and lime as tint plaster. Orange patinas on the window tracery show, instead, the presence of Ca-oxalates, abundant weddellite, and minor whewellite, with minor hematite suggesting the yellowish/orange color as being due to Ca-oxalate patinas imbedding soil dust airborne particles. Such patina was possibly formed naturally either by the chemical attack due to atmospheric air pollutants from traffic exhausts emissions or by bacterial activity. No delamination was observed on the window tracery sample with granular decohesion as the major decay phenomenon. A comparison was made between this patina and the so-called scialbatura, a surface yellowish coating often found by conservators on limestone and marble in ancient monuments in the Mediterranean region.
Subject(s)
Air Pollutants , Citrus sinensis , Calcium Carbonate/chemistry , Calcium Sulfate , PortugalABSTRACT
Fire gilding and silvering are age-old mercury-based processes used to coat thesurface of less precious substrates with thin layers of gold or silver. In ancient times, these methods were used to produce and decorate different types of artefacts, such as jewels, statues, amulets, and commonly-used objects. Gilders performed these processes not only to decorate objects but also to simulate the appearance of gold or silver, sometimes fraudulently. From a technological point of view, the aim of these workmen over 2000 years ago was to make the precious metal coatings as thin and adherent as possible. This was in order to save expensive metals and to improve the resistance to the wear caused by continued use and circulation. Without knowledge about the chemical-physical processes, the ancient crafts-men systematically manipulated these metals to create functional and decorative artistic objects. The mercury-based methods were also fraudulently used in ancient times to produce objects such as jewels and coins that looked like they were made of silver or gold but actually had a less precious core. These coins were minted by counterfeiters but also by the official issuing authorities. The latter was probably because of a lack of precious metals, reflecting periods of severe economic conditions. In this Account, we discuss some representative cases of gold- and silver-coatedobjects, focusing on unique and valuable Roman and Dark Ages period works of art, such as the St. Ambrogio's altar (825 AD), and commonly used objects. We carried out the investigations using surface analytical methods, such as selected area X-ray photoelectron spectroscopy and scanning electron microscopy combined with energy-dispersive spectroscopy. We used these methods to investigate the surface and subsurface chemical features of these important examples of art and technology, interpreting some aspects of the manufacturing methods and of disclosing degradation agents and mechanisms. These findings may contribute to cultural heritage preservation, thus extending the applicability of the surface analytical techniques.
ABSTRACT
The sealing ability of gutta-percha/sealer root canal filling was compared to a new thermoplastic synthetic polymer-based obturation material (Resilon), using a microleakage model and a new sequence detection assay One Cut Event AmplificatioN (OCEAN). Eighty-eight extracted human teeth, shaped with K-Files and the ProTaper Technique, were randomly assigned to four groups (n = 22) and obturated in the apical 5 mm. Group R were obturated with the Resilon/Epiphany technique; group GP were obturated with gutta-percha and Zinc oxide eugenoe sealer; group RCH and GPCH received calcium hydroxide intracanal medication before being obturated. Sterilized specimens were inoculated with Enterococcus faecalis and incubated in sterile medium for 47 days. DNA extracted from the specimens was amplified by PCR and then identified by the OCEAN technique. Samples obturated with Resilon root canal filling material showed a greater number of microleakage events than the other groups (p = 0.036). Calcium hydroxide medication did not have a relevant impact on the quality of the apical seal (p = 0.044).
