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. Discovered mosaics were usually lifted and stored in museums. Some have been presented in archaeological parks. Those in situ mosaics are, although usually covered during winter months, exposed to changing temperature and humidity levels through the year, and exposed to deterioration due to numerous visitors in the summer months. Often tesserae are ceramics, not stone, thus making the mosaic even more susceptible to climatic and other influences. The monitoring and maintenance of in situ mosaics is demanding both in financial resources and specialists available. 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: 2076007In the scope of research work an investigation has been performed into the contributions of various commercially available and in laboratory prepared transparent coatings on the effectiveness of protection of different stone materials. According to their function, transparent coatings were hydrophobic or photocatalytic. The characteristics of these coatings were investigated using the following test methods: visual assessments, colorimetry, measurements of the contact angle, determination of photocatalytic activity, and durability. The results of these tests showed that the effectiveness and durability of the photocatalytic or hydrophobic action of the coatings depended on the investigated type of substratum. For ptrotection of both investigated limestones we determined the optimal coatings.
F.27 Contribution to preserving/protecting natural and cultural heritage
COBISS.SI-ID: 2101863Postojna 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.
F.17 Transfer of existing technologies, know-how, methods and procedures into practice
COBISS.SI-ID: 37798189