Читать книгу Monument Future - Siegfried Siegesmund - Страница 224

Considering the overall results of the petrographic and isotopic analysis of the four marbles, it is 156possible to conclude that they were carved out of the white Dokymaean marble. Two of them (A and D) originated from the same quarrying locus, while the marble of column C was extracted from a different quarry. The provenance of column B could not be positively identified but likely comes from an unknown ancient Dokymaean quarry. The ancient quarrying area of Docimium was one of the largest of Roman and Byzantine times, active from Late Hellenistic to at least the X c. (Pensabene 2011:131) adding weight to our hypothesis. This quarry has been massively re-exploited in modern times and is now the largest white marble supplying area in Turkey. It may well be that one or more ancient quarries have been completely destroyed by modern exploitation therefore escaping study and sampling by archaeologists and archaeometrists. The high quality of the Dokymaean marble, namely its uniform fine grain size, allowed the two sculptors to obtain the beautiful details of the small figures narrating the life of Christ and Mary. The different quarries of origin of the marbles support Weigel’s hypothesis of Byzantine re-use of the four columns, pillaged from an ancient Roman monument. Dokymaean marble was often used for prestigious statuary, portraits (Attanasio et al.2019:178), sarcophagi and architectural elements, and widely exported from its quarries especially in all the Microasiatic provinces (Monna and Pensabene 1977:29–71).

As for the gildings present on the columns, the first and most ancient one was made of two layers: a thicker yellow stratum obtained by mixing a small amount of orpiment, minium, cinnabar and yellow ochre to lead-white (Gettens et al. 1966), and a much thinner one of the same white pigment mixed with a proteinaceous medium. This type of preparation is quite unusual, similar only in colour to those found on the contemporaneous sculpted external arches over the main portal of the Basilica (Lazzarini 1979: 60) (Lazzarini 1995: 232–234). In both structures, the second gilding was obtained in the same way by applying a gold leaf on a minium ground, indicating similar re-gilding of internal and external sculptures of St. Mark’s. Analysis of the brown organic medium impregnating all the superficial layers of the columns revealed a composition of discoloured dammar, a resin much used for consolidating and protecting ancient gilding. This resin began to be used in the West as a varnish for paintings in the first half of the XIX century (Mills, White, 1994: 107), therefore we suggest this conservative treatment should be dated after that period.

Figure 9: FTIR spectrum of the brown patina of sample A1, showing all the peaks of dammar.

The present aspect of the four columns of the St. Mark’s ciborium is far from being satisfactory. The brown patina which almost uniformly covers both areas where gilding remains as well as the exposed marble surfaces, reduces both the impact and legibility of the figures narrating the lives of Christ and Mary and the beauty of the sculpture which leads us to suggest a thorough but delicate cleaning.