ELAICH - Educational Linkage Approach in Cultural Heritage.
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Historic materials of architectural surfaces: Mosaics
1. Educational Linkage Approach In Cultural Heritage Prof. Antonia Moropoulou - NTUA – National Technical University of Athens Knowing the built heritage Module 2 Basic Cour s e Teaching Material Topic 2 . 6 Introduction to the main historic decorative materials Mosaics Educational Toolkit
3. Prof. Antonia Moropoulou - NTUA – National Technical University of Athens Abstract The current presentation examines one of the main historic decorative materials, the mosaics. Mosaics are architectural surfaces covered by a decorative layer consisting of tesserae (small pieces of colored glass, stone or other materials) that are attached to the surface by use of a mortar. Mosaics are subjected to various environmental factors, especially those exposed at the exterior of a building. The conservation of mosaics can vary in extent, from minimum to complete removal of the mosaic, conservation of the tesserae in lab, replacement of the bedding mortar and reattachment to the surface. The respective processes are demonstrated in the current presentation. Educational Linkage Approach In Cultural Heritage
4. Prof. Antonia Moropoulou - NTUA – National Technical University of Athens Content Educational Linkage Approach In Cultural Heritage Table of contents of this presentation 2.6 . 1 Definition of mosaics 2.6.2 Tesserae 2.6.3 Layers and construction materials 2.6.4 Decay of mosaics 2.6.5 Conservation of mosaics 2.6.6 Diagnostic study of mosaics
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6. Educational Linkage Approach In Cultural Heritage 2.6.2. Tesserae Type of mosaics based on tesserae pattern and construction Acropolis of Athens The laying down of the tesserae is known traditionally as the "opus." Different opus result in a different flow or look of the piece Examples Opus tessellatum: Mosaic technique that involves the use of tesserae of uniform size applied to a ground to form pictures and ornamental designs. It was the most commonly used technique in the production of Hellenistic, Roman, early Christian, and Byzantine mosaics. The earliest mosaics in opus tessellatum were composed of stone and marble tesserae, but, in the course of the 2nd century, tesserae of coloured glass were introduced for special colour effects. In the Hellenistic period (3rd to 1st centuries bc) in cities in Greece, Africa, Sicily, and Italy, more commonly, opus tessellatum was reserved for decorative borders surrounding emblēmata, or central figural panels executed in opus vermiculatum, a finer mosaic work using much smaller tesserae. Beginning with the 1st century ad, however, figural opus tessellatum was increasingly used to cover whole floors, and by the early Christian period it had become the dominant technique. With the widespread use of monumental wall mosaics that began with that era, opus tessellatum entirely replaced opus vermiculatum, being much better suited, with its large tesserae and rougher visual effect, for viewing at a distance. Glass tesserae were used almost exclusively for these wall mosaics, and glass opus tessellatum remained the common mosaic technique throughout the Middle Ages. Opus vermiculatum : Type of mosaic work frequently used in Hellenistic and Roman times, in which part or all of a figural mosaic is made up of small, closely set tesserae (cubes of stone, ceramic, glass, or other hard material) that permit fine gradations of colour and an exact following of figure contours and outlines. The word vermiculatum (“wormlike”) refers to the undulating rows of tesserae that characterize this work. Opus vermiculatum was generally used for emblēmata, or central figural panels, which were surrounded by geometrical or floral designs in opus tessellatum, a coarser mosaic technique with larger tesserae; occasionally opus vermiculatum was used only for faces and other details in an opus tessellatum mosaic. Opus Alexandrinum : Type of decorative pavement work widely used in Byzantium in the 9th century. It utilized tiny, geometrically shaped pieces of coloured stone and glass paste that were arranged in intricate geometric patterns dotted with large disks of semiprecious stones Opus signinum : Type of simple, unpatterned or roughly patterned pavement commonly used in Roman times. It was composed of river gravel, small pieces of stone, or terra-cotta fragments cemented in lime or clay. Prof. Antonia Moropoulou – Topic 2.6: Mosaics Ibid
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8. Educational Linkage Approach In Cultural Heritage 2.6.3. Layers and construction materials Wall Mosaics First layer: The layer in contact with the masonry consisted of lime, river sand, coarse crushed brick or tile, earth of Thera and straw Second layer: It consisted of lime, river sand, coarse crushed brick or tile, marble dust, earth of Thera, finer straw and albumen. Third layer: This was the tesserae positioning layer, and it consisted of lime at higher proportions than in the previous layers, river sand, marble dust, earth of Thera and albumen Detail of Empress Zoe, Christ & Emperor John II Mosaic, Hagia Sophia - South Gallery, Istanbul, (Photo courtesy of A. Moropoulou) Prof. Antonia Moropoulou – Topic 2.6: Mosaics Ibid
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19. Educational Linkage Approach In Cultural Heritage 2.6.6. Diagnostic Study of Mosaics Prof. Antonia Moropoulou – Topic 2.6: Mosaics See Module 2 – ADVANCED Diagnostic study of Hagia Sophia mosaics Prof. A. Moropoulou, NTUA For more information: Hagia Sophia mosaic – Upper South Gallery - Photo courtesy of A. Moropoulou ELAICH – Istanbul Experimental Course: Hagia Sophia - In situ use of Non Destructive Techniques to assess the decay state of mosaics and reveal the presence of plastered mosaics
