Many ancient mosaics in Slovenia are found in Roman towns (Emona, Celeia, Poetovio, Neviodunum/Drnovo), smaller settlements (Črnomelj), and in suburban, rural (Mošnje, Šentpavel), and maritime villas (Izola). Mosaics from Slovenia are dated from early Roman (1st century) to early Christian mosaics from late 4th and 5th century. They usually covered up to 20 % of the floor surfaces in a richly decorate churches and town houses, mainly in dining rooms, bathrooms and other representative spaces. Numerous mosaics were in almost 2000 years exposed to the degradation and natural decay; however, many of the mosaics discovered in the end of the 19th and beginning of the 20th century were relatively well preserved in the soil. The external mosaic surfaces can be protected from detrimental weather and other environmental effects by means of transparent functional coatings, which work on the principle of photocatalysis or superhydrophobicity. However, it is necessary to retain the authenticity of these historical materials, as well as providing as durable protection as possible. In this work, various commercially available transparent coatings were investigated in order to determine their functional properties. For that purpose, effectiveness of protection of selected coatings was tested on model mosaics samples made of black and white limestone tesserae, as well as on samples of black and white limestones and brick. According to their function, transparent coatings need to be hydrophobic or photocatalytic. The characteristics of these coatings were investigated using visual assessments, colorimetry, measurements of the contact angle, and determination of photocatalytic activity. The visual assessments and colorimetry were used to determine any observed changes in colour and shine of the surfaces of mosaics after the application of the coatings, whereas the measurements of the contact angle and of photocatalytic activity were performed in order to determine the coatings' effectiveness. The durability of the photocatalytic and hydrophobic actions of the coatings was investigated by exposing the test samples to natural ageing in the archaeological park and accelerated ageing with wet freeze – thaw cycles. Suitability of coatings was determined according to (1) the lowest visual and colour change after application and after aging, (2) the highest contact angle after application and the lowest drop of contact angle after aging for hydrophobic coatings and (3) the highest photocatalytic activity after application and the lowest drop of photocatalytic activity for photocatalytic coatings. Based on results the most promising hydrophobic and photocatalytic coatings for protection of mosaics have been found.
B.04 Guest lecture
COBISS.SI-ID: 2076007Postojna Cave, which is visited annually by more than 500,000 tourists, is exposed to prolonged illumination periods. The illumination is reflected in dense colonization of phototrophic oranisms around lamps. Since 2011, these areas are subjected to removal by a buffered solution of hydrogen peroxide. LED lights, which were intended to replace the existing halogen ones, in the growth experiment in a cave did not significantly contribute to the reduction of algal biomass.
B.04 Guest lecture
COBISS.SI-ID: 37798189Biodeterioration (disintegration of stone surfaces due to organism activity) in modern structures and cultural heritage is a problem that does not only affect the aesthetic appearance of stone elements but also changes their functionality (e.g. building protection) and indirectly influences the economy (e.g. cleaning costs, costs of impregnation agents protection, costs of renewal). Bioreceptivity is a material's susceptibility for the population of living organisms. Methods for bioreceptivity determination are usually based on a quantification of a grown microbiological mass on an exposed stone surface in a determined time. In this thesis a method for bioreceptivity determination is implemented based on an image analysis of autofluorescing pioneer organisms with a fluorescent microscope. The method is primarily meant for assessing the direct influence of a rock's own intrinsic features (e.g. mineral agents, porosity, etc.) on its sensitivity for organism growth. Bioreceptivity has been determined on fifteen frequently used commercial types of natural stone for construction purposes in Slovenia. Mineral composition, petrographic and microstructural features were determined with the help of optical microscopy and other complementary methods (water absorption due to capillary rise, porosimetry with mercury). The rock samples were inoculated (spread) with the following phototrophic organisms: Chlorella vulgaris, Chroococcus minutus and Pseudococcomyxa sp. and exposed to a growth chamber for four weeks. Due to the fastest growth and for counting cells of a proper form and size, the most appropriate microorganism for the laboratory experiment of bioreceptivity proved to be Chlorella vulgaris. It was established that different rocks have a different bioreceptivity which depends on their mineral composition, roughness and physical features, e.g. porosity, and can be assessed in laboratory conditions. In case of dry surface samples, it is important to have a permanent water supply which is provided by the water absorption through the capillary pore system (pores which are less than 0,1 micrometer in diameter). The largest cell growth was registered on sandstone and tuff which are more porous and where the capillary rise is the strongest. It has been established that in case of dry surface samples a) the soaking of the surface, which depends directly on surface roughness and chemical composition, and b) the pore type (rocks with capillary pores prevent drainage and enable a longer water presence on the rock's surface) have the greatest influence. The results of bioreceptivity analysis examinations of water saturated samples show the prevalence of a rock's mineral composition. The growth results are higher in water saturated samples. It can be concluded that water availability is the key factor for cell growth.
D.11 Other
COBISS.SI-ID: 1275230Cultural heritage materials can be protected from deterioration by means of various transparent layers that work on the principle of photocatalysis or hydrophobicity. It is necessary for the protective coatings to be durable, which means providing their functionality for as long as possible, as well as retaining the authenticity of the historical materials. In this master's study we determined the effectiveness of the protection in the case of selected substrates that often appear in structures belonging to cultural heritage, e.g., limestones, tuff, marble and wall paintings, using fourteen transparent coatings, either commercially available or prepared in the laboratory. The effectiveness of these coatings was investigated using the following test methods: visual assessments, colorimetry, determination of the contact angle and photocatalytic activity, capillary water absorption and scanning electron microscopy. The visual assessments and colorimetry were used to monitor changes in the colour and performance of the surfaces of selected substrates after the application of the coatings, whereas the measurements of the contact angle and of the photocatalytic activity were performed in order to determine the coatings' effectiveness. Using the electron microscope the morphology of the substrate before and after the application of the coatings was observed; while the durability of the selected protected agents and substrates was evaluated by exposing the samples to different environments (natural and accelerated ageing). On the basis of the determined morphological, aesthetic and functional properties, and the durability of the historical materials before and after applying the selected coatings, the optimal combinations for coating historical material were defined and the suitability of the coatings for the protection of cultural heritage was assessed. It was found out that the effectiveness and durability of the protection of the assessed substrates depended on the type of coating used, as well as on the properties of the materials that are being protected.
D.11 Other
COBISS.SI-ID: 1537293763Within the project a workshop was organized for the dissemination of knowledge gained among stakeholders (the conservators, restorers, researchers, designers, architects, students, professors) and industry (manufacturers and installers of natural stone as well as manufacturers of coating agents). Over 40 participants attended the workshop, which was conducted at the Institute for Protection of Cultural Heritage. At this workshop the project results were presented within four lectures: The causes of formation of stains on stone surfaces, identification and quantification of the microbiota on objects of stone natural cultural heritage, identification of certain metabolic and degradation products of visible biological growth on historical and modern stone substrates, coatings for protection of stone surfaces and additionaly procedures for cleaning on selected stone sculptures. The second part of the workshop included a practical demonstration of different methods for cleaning stone surfaces: cleaning dry ice, laser cleaning, cleaning by mechanical tools, cleaning with wraps and sandblasting.
F.18 Transfer of new know-how to direct users (seminars, fora, conferences)
COBISS.SI-ID: 2276199