Malta's prehistoric temples : conservation issues

Malta's prehistoric megalithic temples, which are World Heritage sites, are currently suffering from problems associated with the deterioration of materials as well as structural problems. These problems have been studied for many years. A Scientific Committee set up by the Government of Malta in 2000, identified those elements in the surrounding environment causing deterioration of the site. It was recommended that the sites should be protected by temporary shelters, which would provide additional time for research into the long-term preservation of these sites. The sheltering project should kick off late in 2007. In preparation, Heritage Malta has been since 2005, and is still currently, intensively studying the temples as well as conditions in and around the site. Much of this information has already been fed into the final detailing of the shelters. The data obtained from the environmental monitoring in particular will also constitute important baseline information which will then be used to compare with the altered conditions under the shelters.peer-reviewe

The deterioration of cultural property by airborne pollutants : a case study of a Mediterranean island

The Maltese archipelago is situated in the central Mediterranean, at a distance of 93 km from Sicily, 288 km from North Africa, 1826 km from Gibraltar and 1510 km from Alexandria. It has a total area of ca. 300 sq. km and a coastal length of 50 nautical miles ; the length of the largest island (Malta) is 27 km and its width is 14 km. The second largest island of the group is Gozo, which is 14 km long and 7 km wide. Both islands, and especially Malta, are densely populated.peer-reviewe

Proposal for the nomination of Lower Globigerina Limestone of the Maltese Islands as a "Global Heritage Stone Resource"

The Lower Globigerina Limestone of the Maltese Islands is here being proposed for nomination as a “Global Heritage Stone Resource”. This stone, continuously used for building and sculpture for 6000 years, is well suited to fit this global designation as it is not only of great local cultural, historic and economic importance, but it is also the building stone used in construction of the UNESCO, and hence internationally recognized, World Heritage city of Valletta, as well as the UNESCO-listed Prehistoric Megalithic Temples of the Maltese Islands. The stone was also exported to several European and North African countries especially in the early 20 th century. The entire range of archaeological remains and historic architecture which cover the Maltese Islands have been built in this stone, and encompass innumerable palaces and churches, including the fortified cities of Valletta, Mdina (the old capital of Malta), the Three Cities on the Grand Harbour and the Citadel of Gozo, as well as the vernacular architecture ubiquitous within the village cores all over the Islands. The soft limestone has also been widely used over the millennia for elaborate and extensive sculptural motifs. Practically the only natural resource of the Islands, it continues to be quarried today, and is used not only for new construction, but also for the regular restoration of Malta’s great and imposing architectural heritage, remaining thus an important pillar of the Maltese economy.peer-reviewe

Controlling crystallization damage by the use of salt inhibitors on Malta's limestone

Parallel text in Spanish and EnglishThe main building stone in the Maltese Islands is the Globigerina Limestone, of which the Lower member is commonly used. This occurs in two types, the durable franka and the more easily weathered soll. Two types of fresh franka (bajda (white) and safra (yellow)), as well as fresh soll stone blocks, were obtained, based on the identification by quarry owners. Their designation was confirmed by geochemistry. Physical and mechanical properties of the three were investigated, including uniaxial compressive strength, water absorption by capillarity, permeability and porosimetry. Porosimetry results confirmed outcomes of previous research work. Soll was found to have a lower overall porosity, but a high percentage of small pores with practically no large pores. Some of the tested stones were then treated with a non-toxic phospho- organic compound containing carboxylic moieties as a salt inhibitor and the corresponding non-phosphorylated compound.peer-reviewe

Methodology to identify badly weathering limestone using geochemistry : case study on the lower globigerina limestone of the Maltese Islands

This paper proposes a new objective method to classify building limestone into types of varying durability working on samples that are visually identical in appearance. Geochemical data were obtained for 90 samples of the Lower Globigerina Limestone of the Maltese islands. Multivariate analyses, including cluster analysis, principal components analysis and discriminant analysis allowed the identification of variables Si02 , Al203 , K20, Ti02 , Fe203 as indicators to distinguish between more durable 'franka' limestone and the less durable facies locally called 'soil'. This hypothesis was confirmed by differences in geochemical data from samples of both weathered and unweathered stone taken from abandoned quarry faces. In the less durable 'soll', Si02 concentrations are >3.4±0.3%, Al203 >0. 78±0.05%, K20 >0.13±0.01 %, Ti02 >0.06±0.002% and Fe20 3 >0.47±0.02%. However, some overlap occurs between the two stone types for all five components, demarcating another stone type we designated as 'intermediate'. The geochemical differences are reflected in mineralogical data and in acid-insoluble residues. This geochemical method is simple and innovative. It can be used to identify newly extracted limestone for use in building and also for replacement of deteriorated stones in old buildings.peer-reviewe

Investigating a method to limit damage in Globigerina Limestone, a soft porous stone widely used in historic buildings

A programme of studies is ongoing to investigate the action of environmentally-friendly functionalized polycarboxylates as organic crystallization modifiers on salts on two types of Globigerina Limestone of Malta, to compare their action and behaviour. This was mainly done to verify the potential of such compounds to control, and therefore, limit damage on this locally unexplored territory. The main thrust of the research, at this stage, was to observe modifications to solution transport and salt crystal growth induced in two varieties of the stone by treating under controlled laboratory conditions; work under uncontrolled conditions has also commenced, but will not be discussed here. In this paper, indications of the modifications obtained are discussed, in the context of former trials, the fact that they are still under investigation and with a view on way forward. A discussion establishing a classification for damage limitation is postulated.peer-reviewe

Evolving townscapes and landscapes within their settings: managing dynamic change

San Pawl Milqi is found in the north-eastern part of the island of Malta next to Salina bay and overlooking Burmarrad valley. The site was originally situated on an important harbour that is now silted, and was surrounded by agricultural land. The area is rich in archaeological remains belonging to different periods. The boundary wall of the multi-cultural site incorporates an area of approximately 4000 m2. Within this area there is evidence of prehistoric settlement, punic farmhouse, a rural villa belonging to the end of the 2nd century B.C. and evidence of a later period from the 1st to the 11th century A.D. There is evidence that at least two churches were constructed on site. The potential and value of San Pawl Milqi is historical and archaeological, scientific, didactic, social and religious and most importantly a very good example of an ever changing cultural landscape. Recently there have been attempts in studying the environment of the archaeological remains that are exposed together with the environment of the archaeological remains that are underneath the existing structure of the church. A conservation plan for the site was also being set up that was intended to lead to the presentation of the site to be public due to a museographical project.peer-reviewe

Degrado e problematiche conservative di un dipinto ad olio su pietra a Malta

This article provides a sumtnary of the diagnostic study undertaken on an oil-based painting on a dome of a church in Malta. Painted in 1903 and extensively restored in 1963, this mural is now found to be in an appalling condition. To investigate causes and processes of deterioration, a multidisciplinary approach was followed. This included historical research, non-invasive examination, sampling and analysis, and environmental monitoring. Soluble salts, mainly gypsum and minor amounts of halite, were found to be the main causes of deterioration. Salt crystallization cycles were triggered by recurrent and prolonged rainwater infiltrations, whilst solar radiation may have played a role by increasing the number of crystallization cycles. Deterioration was also favoured by intrinsic factors. Oil-based paintings applied to porous materials, in this case a very porous limestone, create a barrier to the passage of water, and favour the formation of an interface between the wall and the paint layer, under which salts may crystallize. In this case, the artist applied his painted strata over pre-existing paint layers making the painting's structure even more prone to delamination. The limestone over which the painting was applied was found of bad quality and susceptible to salt decay. The difficult issues in relation to the preservation of this painting are referred to and are open for discussion.peer-reviewe