An Assessment of the Role of an Open Shelter in Reducing Soiling and Microbial Growth on the Archaeological Site of the Bishop’s Palace,Witney, England

Two sets of twelve Portland limestone tablets were attached to carousels outside and under the open, lightweight shelter at Bishop’s Palace (Witney, England) for 18 months to assess the influence of shelters on soiling and microbiological growth on stone. At the start, and at 6-month intervals, tablets were analysed using microscopy (optical and SEM), colour measurement (spectrophotometry), weight change measurement and salt content determination (ion chromatography). Concentrations of NO₂ and SO₂ were also monitored for a month using diffusion tubes. In addition, results were compared with those obtained by the UK National Materials Exposure Programme (NMEP) on chemical weathering rates. Differences in soiling and biological growth on sheltered and unsheltered samples, and their influence on limestone decay were established. The shelter is likely to reduce biological growth by modifying the micro-environmental conditions. However, it may also exacerbate dust deposition, which might increase decay rates in the long-term.     

Determining the provenance of black limestone artifacts using petrography,isotopes and EPR techniques: the case of the monument of Bocco

This paper investigates the provenance of the black limestone of the monument known as Bocco, named after the king of Mauretania who presented Silla with this work as a sign of his submission to the power of Rome. A multi-method approach, comprising petrographic observations, carbon and oxygen isotope composition and electron paramagnetic resonance (EPR) spectra characteristics, was used for this purpose. The monument is part of a reconstruction of a rectangular base (approx. 8 × 2 m) which is likely to have served as the base for a bronze statuary group and is currently composed of six blocks of limestone whose exterior is engraved with a fine frieze. The results of the different analyses were compared with the data of a published database of the most important black limestone quarries exploited during Roman times in the Mediterranean area. The petrographic and physico-chemical parameters did not prove to be very effective in determining the provenance of the black limestone of Bocco; the isotopes result even raised some uncertainty as to whether all six blocks came from the same quarry, though this doubt was dispelled by the EPR data and, above all, by the evident petrographic similarity between them. Differences in the isotopic composition of the various blocks may be due to an in situ rock alteration process caused by interaction with an aqueous fluid. It was, however, impossible to determine with certainty the origin of the material of the stone artifact using the database available; it is possible that the black limestone of Bocco came from an ancient quarry that is likely to be located in north western Africa but has not yet been uncovered. An alternative hypothesis, according to which the limestone used for the monument of Bocco came from the ancient quarry of Ain el Ksir, one of the Tunisian quarries present in the database, is also discussed.     

Decay of Limestone Statues at Mount Nemrut (Adiyaman,Turkey)

Mount Nemrut is a 2,206 m high mountain located in Adiyaman, Turkey. A number of monumental statues, a 50-m high tumulus, and a lion horoscope were constructed at the top of the mountain by King Antiochos I (69–36 bc) of the Commagene Kingdom. The site was included in the UNESCO World Heritage List in 1987 due to its unique character. However, the limestone statues located on both the east and the west terraces of the site are getting deteriorated. This study investigates the weathering of the limestone at Mount Nemrut based on field and laboratory studies. It is found that the dissolution occurs along microcracks developed in the limestone during geological time. It is more pronounced in the east terrace where freezing-thawing cycles are more than the west terrace. Furthermore, dissolution is more effective for the faces of the statues exposed to direct atmospheric contact. Due to harsh atmospheric conditions with dominant wetting-drying and freezing-thawing processes at the site, it is recommended that direct rain and snow contact with the statues should be minimized.     

Preparation of a new calcite layer from calcium glycolate for the conservation of sulfated limestone artifacts

A novel preparation method of calcite layer was explored for the conservation purpose of the surface sulfation limestone artifacts. In this method, the alcoholic solution of calcium glycolate was used as a precursor of calcite layer. After application on the surface of gypsum crust on limestone by spraying, calcium glycolate can combine with the carbon dioxide spontaneously and form a compact calcite layer. The obtained calcite layer can act as a shelter and can prevent the gypsum crust from the dissolution damage of the natural precipitation. The protective properties of the calcite layer were investigated by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS), X-ray diffraction (XRD), infrared spectroscopy (FTIR), water erosion resistance, water absorption, colour difference, surface strength, and hardness test. The results revealed that the water erosion resistance, surface strength, and hardness of the treated sample were increased remarkably. Meanwhile, the intrinsic physical properties such as porosity, capillary absorption, and appearance were not affected obviously, indicating a good compatibility of the proposed protection method.     

Paper 5: Historic Mortars from the Coudenberg Archaeological Site: Characterization and Source of Raw Materials

Abstract

The characterization of historic mortars by means of a concise methodology of material analyses can provide crucial information with regard to the origin of the raw materials and the ancient mortar technology. For the analysis of the historic mortars of the Coudenberg archaeological site, the methodology consists of optical and scanning electron microscopy, simultaneous thermal analysis, and an acidic treatment. These analyses were carried out on a total of seventeen samples lifted from various areas in the site, in function of the building chronology resulting from a historic built investigation. The type of binder and aggregate as well as their volumetric ratio were determined.

Both binder and aggregate present distinctive features, which made it possible to identify the probable geological provenance of the raw materials. The observations are verified with available historical records regarding the construction of the main banqueting hall — the Aula Magna — and the use of raw materials such as limestone and sand for the production of lime and construction purposes.     

Reconstruction of the Rib Vaults of the Hypostyle Hall in the Maniace Castle of Siracusa After the 1693 Earthquake

Built in the first half of the 13th century on behalf of the Emperor Frederick II, the Maniace Castle of Siracusa focuses its enigma in the hypostyle hall (which was composed of 25 quadripartite rib vaults) and the design criteria adopted for its implementation. Recent research and a careful rereading of the documentary “restoration project” after the earthquake of 1693 have offered new tools to understand the construction techniques and building procedures for the entire organism. It has been possible to demonstrate that the different material (white limestone and volcanic stone) used for the vaults is, in fact, a product of reconstruction. The constructive node, which historiography has taken for granted, is now crucial—the documentary evidence of the restoration after the earthquake compared with the materials found in situ provide interpretive keys to decode genesis and procedures of the huge structure built five centuries before.     

Pollution Monitoring for Sea Salt Aerosols and Other Anionic Species at Hagar Qim Temples,Malta: A Pilot Study

The damaging effects of sea salt aerosols on Globigerina Limestone are well known, and various professionals have studied and reported on the often complex underlying deterioration mechanisms. Following a preventive conservation project, undertaken to shelter and protect the UNESCO World Heritage Neolithic temple sites of Hagar Qim and Mnajdra, the Preventive Conservation Unit within the Diagnostic Science Laboratory at Heritage Malta embarked on a pilot study to identify whether sea salt aerosol deposition patterns within the site alter significantly post sheltering. The results from this short pilot study, by identifying the presence of salts using ion chromatography, have shown that there is a consistent pattern that when directly linked to the intrinsic shape of the temple interior as well as to the micro-environmental factors that are changing as a direct result to the sheltering, point to the trends of greater pollutant accumulation, particularly dust.     

The Influence of Salt on Handheld Electrical Moisture Meters: Can They Be Used to Detect Salt Problems in Porous Stone?

Salt contamination in heritage stone affects handheld moisture meter measurements on-site. This poses a problem when the readings indicate erroneously higher levels of moisture than actually present. For decision making with regards to moisture prevention treatment it is therefore crucial to distinguish between actual dampness and the hygroscopic action of salts. This study investigated the effect on moisture meter readings of both increased conductivity of pore water and the increased water retention caused by the presence of sodium chloride (NaCl) in artificially contaminated Portland limestone samples. The influence of NaCl contamination on selected handheld moisture meters was quantified. As a result, this article proposes that under certain circumstances moisture meters could be used to diagnose, reliably, both moisture and salt problems in heritage stone.     

The Dilmun temple on Failaka,Kuwait

The Kuwaiti‐Danish 2009 excavations on Failaka produced new evidence for the dating of the Dilmun temple in Tell F6. The affinities of this temple to the Barbar temples in Bahrain are emphasised, whereas the hypothesis of a Syrian‐inspired temple tower is questioned.