Technology Features and Recommendations of the Dalphni Monastery
The Daphni Monastery was built in 11° century and the décor includes the most famous mosaics of the Byzantine period. Analysis of glass mosaic tiles and other building materials of the monastery took place in order to find methods and materials for mounting, maintenance and preservation.
The purpose of the analysis also was to identify compositional characteristics and technology of glass mosaic tiles and be associated with other spectacles technologies Byzantine period. Specifically made comparisons between the technology of glass mosaic of the Monastery of Daphni and glass mosaic of the Monastery of Saint Luke.
During maintenance study the mosaic of the Monastery of Daphni glass mosaic of different colors gathered and analyzed in order to determine or chemical composition. The results of the analysis provided the information on:
- The type of glass,
- The type and sources of alkali raw materials,
- The colorants and opacifiers used.
The glass mosaic of the Monastery of Daphni is glasses type silica-soda-lime (silica-lime-soda) (or else type “natron”) and owe their color to different concentrations of oxides of iron, copper and manganese.
Then the results were comparisons between the glass mosaic of the Monastery of Daphni and those of the monastery of Saint Luke. According to this comparison, the two categories of glass mosaic tiles have similar recommendations, and glass mosaic tiles have different compositions, in comparison with other Byzantine glass mosaic of the 5th and 6th centuries.
Finally, the analysis showed that the glass mosaic tiles and glass mosaic tiles have been used newer glasses during previous maintenance interventions, made in the late 19th century. and throughout the 20th century.
Description of sample
Samples of glass mosaic tiles collected during maintenance study the mosaic of the Monastery of Daphni and selected representative colors opaque and transparent glass. The glass mosaic tiles in a wide variety of colors and shades.
In stereo-microscope transparent glass inlay had bubbles and some of these white granules. Unlike opaque glass mosaic pieces had small fossil fragments were used as colorants. It was then observed that the glass mosaic of different colors were heated together to generate newer. Eventually the surfaces of most glass mosaic tiles are very pitting and a lot of thin solidified ingress of atmospheric corrosion.
Results of the analysis
Analyses were performed using X-ray fluorescence (XRF) in the Instituto di Ricerche Technologiche per la Ceramica Ravenna.
The glass mosaic of the Monastery of Daphni is typically silicon type glasses-calcium -sodas (silica – lime – soda), with a relatively high proportion of magnesia (MgO). The lead oxide (PbO) is sometimes observed as a sharper network is a low rate with the exception of three samples have high levels, ie. 4.05%, 5.46% and 7.70% by weight.
The samples also contained manganese oxide (MnO) to a range between 0.3 and 2.5% by weight and also low rates of potash (K2O).
The different composition glass mosaic form distinct groups according to their origin.
Colorants and opacifiers
The main data used as colorants in glass mosaic of the Monastery of Daphni is iron oxide (Fe2O3), copper oxide (CyO) and manganese oxide (MnO). The lead oxide (PbO) was observed at high concentrations in the case of the two opaque glasses green (7.70%) and the deep blue. (4.73%).
Antimony (Sb) and zinc (Zn) were used at different concentrations as main deactivators in green glasses and antimony and tin (Sn) used in deep blue and red glasses
The establishment of different green glass mosaic varies and different color shades directly related to high concentrations of copper oxide (CyO) (between 0.64 and 5.21% by weight) and high concentrations of manganese oxide (MnO) (more than 2, 59% by weight). The opaque green glasses owe their color to the high concentrations of lead oxide (PbO) (7.70% by weight) and antimony oxide (Sb2O3) (3.12 wt%). (photo 1)
Opaque red glass mosaic tiles containing a high concentration of iron oxide (Fe2O3) (3,87% by weight) and have similar composition with those of Saint Luke
The color of the individual ink-chip due to the combined action of manganese oxide (MnO) (2.11 wt%) of iron oxide (Fe2O3) (0.92% by weight).
Finally, the deep blue glass mosaic containing a low proportion of cobalt (Co) and a high percentage of lead oxide (PbO). (photo 2)
As shown in the tables and diagrams of chemical data of glass mosaic tiles of Daphni, shown little dispersion and some of them have different recommendations, apparently because of their different origin. Some of the glasses show newer recommendations and apparently used in previous maintenance interventions, while other glasses have ancient recommendations and possibly reused.
In the first case known to early last century additions were parts of the mosaic surfaces, while for the second case, unfortunately, there are no accurate figures when these procedures were performed. This becomes evident from the maintenance study the mosaics, which were observed different types of mortars and different types of glass mosaic tiles.
According to the analyzes and charts data, most of the glass mosaic of Daphni is identical with those of St. Luke. Also according to the data and charts shown that these glasses are totally different from Byzantine glasses of the 5th and 6th century (as shown in Figure 3) and some of them have similar recommendations with some typical Byzantine glasses. In addition the majority of glass mosaic tiles analyzed, presented higher percentage of silicon dioxide (SiO2) than the Byzantine glasses 5th and 6th centuries.
The first main difference observed between the Daphni glasses and those of St. Luke is the use of lead and tin as deactivators. The complete absence of tin from the glass mosaic of St. Luke (11th cent.) Shows that practically were not available opacifiers based on tin due perhaps to the high cost.
The use of these opacifiers in glass inlay lauric was a result of high growth of the glass art at the 11 ° century and the availability of previous raw materials. The quality of glass mosaic demonstrates that the fabrication techniques developed in a satisfactory level in relation to the quality of the mosaic.
The range of colors is however limited due to the ability of psifotheton produce specific colors. Differences in glass recommendations had to do on the ability of psifotheton to salvage and recycle materials from other mosaics and other glass constructions.
Finally, it should be noted that it is necessary now to build a large-scale database on the glass manufacturing technology and mosaics during the Byzantine period. For this purpose it is necessary to obtain, analyze and compare glasses by most known monuments in a wide range of colors, to which can assist and colleagues archaeologists, who can facilitate the collection of such data when needed.