Anna Maria De Francesco

Archaeometric study of black-coated pottery from Pompeii by different analytical techniques

Complementary spectroscopic methods were used to characterize ceramic body and black coating of fine pottery found at Pompeii (Italy). This has enabled us to investigate local productions and to clarify the technological changes over the 4th-1st centuries BC. Two different groups of ceramics were originally distinguished on the basis of macroscopic observations. Optical microscopy (OM), X-ray diffraction (XRD) and X-ray fluorescence (XRF) seem to indicate the usage of the same raw materials for the production of black-coated ceramics at Pompeii for about three centuries. Raman microscopy (RM) and micro-analysis (SEM/EDS) suggest different production treatments for both raw material processing and firing practice (duration of the reducing step and the cooling rate).

Strength anisotropy in building granites

ABSTRACT Throughout history, natural stones have been used as building materials in the architectural heritage. The purpose of this research is to assess the influence of anisotropy on building granites’ behavior. This article deals with San Giovanni in Fiore granite (Italy). Samples are subjected to several tests, namely: petrographic analysis; ultrasonic P-waves velocity; uniaxial compressive, flexural and indirect tensile strength; and point load, with respect to different angles between splitting planes and loading directions. Good strength values indicate that this granite is to be considered as adequate as building material, even though it exhibits an anisotropic behavior. The microcrack systems and their different orientation along the spatial directions, influence the petrophysical and mechanical behavior. The highest strength values are registered for the anisotropic XY plane (Z-direction), for all performed tests. Thus, it can be used in construction whilst considering the anisotropic directions to improve its strength properties and its resistance to decay processes.

UV Fluorescence as tool to evaluate the biotic encrustation pervasiveness on under water amphorae near Crotone (Calabria-Italy)

Underwater ceramic sherds, found in the harbor of Crotone (Calabria, Italy), were analyzed with different analytical methods. The pottery fragments, mostly amphorae, are characterized by a great layer of encrustation on the surface. Archaeological information are very poor, no assumption about provenance and technology, these ceramics are only doubtfully dated to Medieval times. The petrographic (Optical Microscopy) and chemical analyses (X-Ray Fluorescence) on the ceramic of Crotone evidenced a strong compositional heterogeneity. Comparison with literature data supported two different production areas: Western (Southern Italy) and Aegean area. UV Fluorescence on biotic crusts, allows to evaluate the relationship between the biotic colonization and the ceramic paste and to trace the alteration pervasiveness due to the encrusting organisms.

Preliminary petrographic analysis on common ware from Naples

Three different pottery classes found in the monumental complex of Girolomini (Naples) were investigated by petrographic analyses.The studied samples consist of cooking ware and tableware dated between the late fourth century AD and the first half of the fifth century AD. Two groups of ceramics show clear evidences of provenance, while a small group of cooking ware with distinguishable features - typological aspects, surface treatments and fabric – brought more hypotheses about origin.Preliminary petrographic analyses were performed in order to have more information about supplying of the raw materials in the Bay of Naples and in the considered period. The comparison with potential raw materials carried out on the less numerous, but particularly significant ceramic group highlighted new insights about exploitation of the local resources.

An original experimental approach to study the alteration and/or contamination of archaeological ceramics originated by seawater burial

This paper deals with the proposal of an original experimental equipment specifically designed for appraising any compositional alteration of archaeological ceramics after the protracted contact with seawater. A series of ceramic test-pieces (briquettes and cylinders) were purposely manufactured by mixing selected calcareous or non-calcareous clays with different varieties of sieved sand temper. The aim was to reasonably simulate the ceramic pastes most frequently found in the shipwrecks recovered in the coastal areas of western Mediterranean. The used raw materials were previously characterized in terms of mineralogical and chemical composition (XRPD, XRF). The obtained test-pieces were fired under oxidizing conditions at predetermined temperatures (800 and 950°C) in a traditional ceramic kiln and their chemical composition was analyzed by XRF spectrometry. Briquettes were firstly fixed into customized Ertacetal® holders and then placed in open sea-bed environment under monitored oxidizing or reducing conditions by the Italian CNR-IAMC dockside at Granitola, north-western Sicily. At the same time, two customized glass containers for working in a confined system under continuous seawater flow were designed and realized. They were filled with bottom sediments rather different in size in order to produce either reducing or oxidizing microenvironments below the water-sediment interface. Cylinder shaped test-pieces were placed in the sediment of both the glass containers. Weekly monitoring of temperature, salinity, conductivity, pH, Eh, dissolved oxygen was carried out in both the above-described experimental settings. Comparative (before/after) XRF analyses, after 3 months of exposure to seawater, were performed on the experimental ceramic briquettes and cylinders. The obtained results provided preliminary evidences that the proposed experimental apparatus is efficiently working and a number of not negligible changes concerning major and trace elements were pointed out just after such a restricted time of exposure to seawater.