Scientific Examination of Art Modern Techniques in Conservation and Analysis (2005) / Chapter Skim
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An Overview of Current Scientific Research on Stone Sculpture--Richard Newman
An Overview of Current Scientific Research on Stone Sculpture--Richard Newman
Pages 58-71
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From page 58... ...
Authentication of stone sculpture can focus on materials, techniques by which the materials were worked, and weathering layers. The alteration of a sculptural surface and the buildup of alteration products on that surface in a burial environment can be useful as an indication of age, and as such is often studied in stone sculpture authentication projects.
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From page 59... ...
We know in the case of marble sarcophagi in Roman times that blocks were sometimes partially shaped at the quarry and then shipped to various workshops where the final carving was completed. Determining workshop locations is an aspect of research on rock sculptures that can draw on information about quarry sources.
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From page 60... ...
A second phase of research involves characterizing potential quarry sources and then comparing these with results from the artifacts. The goal is to determine the quarries from which the artifact rock came.
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From page 61... ...
. Geologists have long utilized the electron beam microprobe to quantitatively analyze individual mineral grains in thin sections of rocks.
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From page 62... ...
Finished objects, or pieces of rock that were shaped in local workshops, were apparently shipped all over Egypt from the source quarry or quarries. A more recently developed tool for individual mineral grain analysis in thin sections is laser ablation microprobe ICP mass spectrometry.
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From page 63... ...
There are many rocks, however, that cannot be adequately distinguished by petrography, or that contain minerals that do not show sufficient variations in major, minor, or trace element compositions in order to be suitable for microprobe or laser ablation ICP mass spectrometry. Other analytical techniques that can be applied to solid chip samples, whether prepared as thin sections or not, include Fourier transform infrared spectroscopy and Raman spectroscopy.
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From page 64... ...
Both the suite of elements utilized in a sourcing study and the methods by which the data is evaluated are obviously crucial to the conclusions. Limestone in Medieval France One of the most outstanding research projects yet to be published on sculptural rock sources involves the limestone utilized in French medieval sculptures.
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From page 65... ...
Their textures, grain sizes, and minor and accessory mineral compositions provide some useful properties for discrimination, but petrographic properties alone have not been adequate to clearly distinguish most of these marbles. An important breakthrough came in 1972 with a publication by marine geochemists who applied a tool of their trade, stable isotope analysis, to a few samples from several of the major ancient Mediterranean marble quarries (Craig and Craig, 1972)
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From page 66... ...
A brief survey of these techniques serves as an example of how there are diverse, often equally useful approaches to a sourcing problem, and more important, how data from more than one technique may be crucial in solving a particular problem. Although petrography was probably not considered a particularly valuable technique by most researchers for many years, within the last few years one particular property that is best determined with a thin section has been shown to be very useful: maximum grain size.
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From page 67... ...
Some researchers have carefully compared drill marks produced by known ancient drilling procedures with marks produced by modern drills, and this information could obviously be used in certain authentication studies. Tool marks on ancient gemstones have also been extensively studied (Rosenfeld et al., 2003)
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From page 68... ...
The use of tool marks in authentication studies may fall more into the realm of technical connoisseurship, where interpretation of significance depends on the experienced eye of a researcher who has carefully examined many tool marks on many artifacts. One example is in a paper published 13 years ago by a sculptor who has studied tool marks on Roman marble sculptures (Rockwell, 1990)
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From page 69... ...
Some organic materials will undoubtedly be present in authentic weathering layers, but the nature of these and their relative abundance can reasonably be expected to be quite different. A wide range of very sensitive techniques for organic analysis are available, such as gas chromatography/mass spectrometry, which can be applied to characterization of organic residues in rock weathering layers.
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From page 70... ...
The study of marble weathering layers can be taken as an example of the increasing sophistication applied to the problem as time goes by. A little over 30 years ago, when the use of weathering layers on marble as an authentication tool was first suggested, thin sections examined under a polarizing-light microscope were the only tool applied to their study.
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From page 71... ...
There are many sourcing projects on rock sculptures that remain to be undertaken, projects that can potentially be of great importance to art historians and archaeologists. Authentication of rock sculptures has also long been an active area of research, in which advances are continuously made.
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