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Mosaics Seminar


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Mosaics Seminar

  1. 1. M . O . S . A . I . C . S<br />20 April 2010 Maria Bonet<br />
  2. 2. Early History<br />Earliest known mosaics were created in Asia Minor and Greece<br />Intended as sturdy floor coverings<br />Originally constructed principally with black and white pebbles<br />Height of Greek mosaics reached during the Hellenistic age (2nd century BC)<br />Polychrome style popular and widely used<br />Mosaic art introduced to Rome via Greece<br />Monochrome or ‘Black Figure’ style popular<br />Roman style spread throughout Roman Empire to Britain, Africa and the Middle East<br />Wall and vault mosaics were already in use in Greece and Rome, but were principally created by Christian artists<br />
  3. 3. Bath floors, Ostia Antica, 2nd c BC<br />Image taken from<br />‘Dionysus on a Leopard,’ Delos, 2nd c BC<br />Image taken from<br />
  4. 4. Materials<br />Support<br />Layers of soil bedding<br />Brick walls<br />Wood or bone<br />Plaster<br />Lime<br />Sand, pozzolana, clay, <br />brick dust, chopped straw<br />Tesserae<br />Stones (marble, limestone)<br />Glass (Smalto)<br />Ceramic tiles<br />Layer is known as tessellatum<br />Tesserae from Qibbuz Kabri, south of <br />et-Tuweiri. Image taken from Hadashot Arkheologiyot ( <br />
  5. 5. Technique: Floor Mosaics <br />Common bedding layers: <br />First: Rammed earth and un-mortared rubble<br />Second: Opus signinum (crushed tile and lime mortar) or mortared rubble<br />Lime-mortar bedding on which tesserae were imbedded <br />Pictor designs the mosaic<br />Floor area is measured and divided into grids<br />Pavimentare lay the tesserae down. <br />Floor grouted with mortar, then polished with abrasive stones<br />Preparatory layers, ‘Orpheus Mosaic,’ Paphos, Cyprus. Image taken from The Conservation of the Orpheus Mosaic at Paphos, Cyprus<br />
  6. 6. ‘Orpheus Mosaic,’ House of Orpheus, Paphos, Cyprus, 2nd c BC.<br />Image taken from The Conservation of the Orpheus Mosaic at Paphos, Cyprus (1991)<br />
  7. 7. Technique: Wall Mosaics<br />Bedding layers:<br />Brick wall<br />Rendering / foundation bed (sand, pounded brick)<br />Intermediary bed (lime, brick dust and chopped straw)<br />Setting bed (lime and marble dust)<br />Designs were sketched either directly on the brick wall or on the rendering bed<br />Tesserae <br />Smalto , marble, mother of pearl, jewels, gold and silver<br />Interstices between tesserae begin to widen to increase the luminosity of the design<br />Basilica di San Vitale, Ravenna, Italy, 6th c AD. Photograph © 2007 James Martin. Image taken from Italy Travel<br />
  8. 8. Construction of the ‘Cinderella Mosaics,’ Cinderella Castle, Magic Kingdom, Orlando, FL. Photo © Disney. Image taken from<br />Detail, Virgin Mary, Hagia Sophia, Istanbul, Turkey, 944 AD. Image taken from<br />Detail, ‘Cinderella Mosaics,’ Cinderella Castle, Magic Kingdom, Orlando, FL. Photo © 2009 J Spence. Image taken from<br />
  9. 9. Techniques: Other Supports<br />Support: Carved wood or bone<br />Pine or Bursera tree (‘copal’) resins applied to support<br />Tesserae<br />Minerals: Turquoise, jade, malachite, pyrite, lignite <br />Shells<br />Polished by hand with fine sand or fine cane strands<br />Quetzalcoatl, Miztec-Aztec ceremonial mask, Mexico, 14th-15th c AD. Image © The British Museum<br />
  10. 10. <ul><li> Mask support is a human skull with a hinged jaw
  11. 11. Interior lined with leather</li></ul>Tezcatlipoca, Miztec-Aztec ceremonial mask, Mexico, 14th-15th c AD. Image © The British Museum<br />
  12. 12. Deterioration <br />Soluble salts<br />Cause efflorescence and subflorescence, which weaken mortar and adhesives<br />Capillary action brings moisture to the surface<br />Incrustations form from salt migrations, pollution, site specific dirt and previous repairs<br />Process initiated and maintained by fluctuations in temperature and moisture<br />Stress<br />Can be internal (crystal lattices broken as mineral ions react with a given substance) or external <br />Cracks in bedding / mortar causes tesserae to lift, become loose or detach <br />High volume of visitors places external stress on the surface<br />
  13. 13. Deterioration Continues<br />Biodeterioration<br />Root action<br />Bioreceptivity: Porous materials that retain moisture are more prone to biodeterioration<br />Phototrophic bioagents (algae, lichens) encourage growth of bacteria and fungi <br />Moisture is trapped within the material<br />Bacteria<br />Excrete organic and inorganic acids<br />Can produce a protective patina<br />Halophilic bacteria: Thrive on salt-rich environments<br />Fungi<br />Biofilm on weathered stone, microscopic view. Image taken from Conservation Science (2006)<br />
  14. 14. Conservation<br />Cleaning<br />Water can be used to wet clean tesserae<br />Accretions picked off with chisels, dental tools<br />Consolidation<br />Adhesives (Paraloid B72)<br />Cramps inserted into bedding in order to pull together layers that have lost cohesion<br />Grouting: Injection of mortar under the tessellatum<br />Loose tesserae can be removed—one by one—and reattached<br />Infilling and replacement<br />Edging and infilling of lacunae<br />Infill of interstices<br />
  15. 15. More on Conservation<br />Biocides<br />Biostatic or biocidal<br />Quaternary ammonium compounds are both biostatic and biocidal<br />Organism to be fought must be properly identified before biocide is chosen<br />Ethical issues of human toxicity and adverse effects on the stone<br />Prevention<br />Shelters to keep out rainwater and excessive sunlight<br />Coatings<br />Knowledge of the mosaics environment (weather, visitors, seismic activity, etc)<br />Tesserae consolidation. Photograph © 2010 Enzo Aiello. Image taken from<br />
  16. 16. On Lifting<br />Harvard University team members at Sardis, Turkey in 1991. JAIC Online, vol. 39, no. 1. Image taken from<br />Lifting<br />Facing: Cloth is adhered to the surface of the mosaic<br />Rolling: The cloth is stapled to a wooden drum or roller<br />Spillatura: Removal of backing mortar with metal awls, fraises, dental tools, etc<br />Mosaic can then be either displayed in a museum or placed into new bedding in situ <br />Controversy:<br />New bedding layers can settle differently, leading to cracks<br />Metal honeycomb backings can corrode<br />Removal of mosaics to museums is being re-evaluated <br />Current emphasis is on prevention and on in situ repairs<br />
  17. 17. Go ye forth and conserve!<br />THANK YOU<br />Mosaic Art House in Boerum Hill, Brooklyn (c.2009). <br />Image from mosaicartsource.<br />com<br />