Читать книгу Monument Future - Siegfried Siegesmund - Страница 220

The famous four marble columns of the ciborium are among the most important artifacts preserved in St. Mark’s Basilica, Venice. Carved with scenes of Christ and Mary’s lives by two masters in Constantinople in the first half of the 6th century BC, they were subsequently pillaged from an unknown church by the Venetians soon after the 1204 Crusader’s sack of the city. Reworked and gilded in Venice, they were re-installed after the 1222 earthquake in the ciborium covering the sarcophagus of the evangelist and the main altar. Thought to be made of oriental alabaster, they have been subject to many treatments throughout the centuries and the subject of extensive archaeometric study with identification of their materials, previous gildings and protective treatments. Micro-samples taken from each column were analysed by minero-petrographic (XRD, OM, SEM+EDS on thin and polished cross sections) and geochemical (SIRA, microFTIR and Raman spectroscopy) techniques. The results indicate that the columns consist of Dokymaean marble originating from three different quarries.The original gold leaf gilding was applied to a yellowish preparatory layer of lead-white mixed with other pigments subsequently covered by two later gildings, the most recent of which was laid on a red minium-ground. A protective/consolidation film of dammar, now discoloured into a brown coating, was identified together with other organic media such as siccative oils and proteinaceous substances and were probably applied in the XIX century and later.