Detection of Fakes and Copies
When we consider acquiring an object for the Asian Art Museum’s collection, our first step is to focus a trained eye on it. Curators thoroughly familiar with similar objects carefully examine and compare it to others of known age, looking for stylistic similarities and differences. The curators’ experience in this kind of research and their understanding of the context in which the object is supposed to have been made inform their evaluation. Many fakes are detected at this point. Some questions, however, can only be answered through the use of technical examination and scientific analysis.
In much the same way that forensic experts conduct criminal investigations, museum conservators conduct examinations and analyses that can prove objects authentic or unmask fakes and restorations. The two primary approaches used in the detection of fakes are:
- studying the materials and methods of construction to determine if they are appropriate to the apparent age of the object
- studying wear, accretions, corrosion, and other evidence of age
Using a wide variety of approaches and techniques, the Asian Art Museum’s Conservation Center carries out authenticity studies and analyses of materials and techniques used to make objects in the collection. The results not only may confirm or refute an object’s authenticity but also may answer larger art-historical questions or relate the object to others. In many cases, the research process takes us beyond the walls of the Asian Art Museum into the wider art-historical and scientific communities. The Conservation staff has collaborated with researchers at other museums both in the U.S. and abroad as well as with scientific laboratories with sophisticated instruments sometimes needed to supplement our in-house research.
In addition to undoubted fakes and copies, there are more problematic objects. Ultimately there are instances in which neither the art-historical assessments nor the scientific data are conclusive.
Tests We Can Perform in the Asian Art Museum’s Laboratory
BINOCULAR MICROSCOPY. A low-powered microscope with two eyepieces is used to closely examine and treat objects with a precision unobtainable using the unaided eye.
POLARIZED LIGHT MICROSCOPY. A research microscope is used to study tiny samples under high magnification with transmitted light, reflected light, polarized light, and ultraviolet light. An experienced microscopist can identify pigments, fibers, and cross sections of lacquer and paint layers.
METALLOGRAPHY. A special microscope with reflected light is used to examine the structure and corrosion of a small sample of metal from the object.
CHEMICAL SPOT TESTING. Wet chemical tests are carried out on small samples removed from an object to determine its composition. Pigments, metals, fibers, resins, ceramics, glasses, wood, stone, and accretions can be tested using this method.
X-RADIOGRAPHY. X-rays are employed to produce an image on film that can expose filled gaps, cracks, hollows, joins, armatures, restorations, and flaws not visible to the naked eye.
Tests Performed in Outside Facilities
Numerous kinds of highly specialized instrumental analyses are available in laboratories outside the Asian Art Museum. Some of these analyses do not require a sample and leave the object unchanged. Others require the taking of a sample, which is consumed during testing. In order to avoid marring the object, we take only minute samples. Among these tests are:
CARBON-14 (C-14) DATING. This method is used to determine the approximate age of organic materials such as wood and textiles. Over time, measurable changes occur in the ratios among three carbon isotopes naturally present in organic materials.
FOURIER TRANSFORM INFRARED SPECTROMETRY (FTIR). Wavelengths of infrared radiation passed through a sample are selectively absorbed by various kinds of bonds between atoms in the sample. The change in the exiting infrared beam can tell us something about the molecular structure of the sample. FTIR is used to identify organic compounds such as adhesives, binding mediums, resins, and coatings.
INDUCTIVELY COUPLED PLASMA-ATOMIC SPECTROMETRY (ICP). This test is used to analyze metals and their trace elements. A small drilled sample is heated to break it down to its elements, which are quantitatively identified.
SCANNING ELECTRON MICROSCOPY (SEM). In this test, a high-powered microscope produces a beam of electrons (instead of light) in order to reveal the microstructure of a sample taken from an object.
THERMOLUMINESCENCE (TL) TESTING. This test measures the amount of accumulated radiation released by natural crystal “traps” in ceramic samples as they are heated. The test is used to date fired ceramic objects and the ceramic cores of metal castings.
X-RAY FLUORESCENCE (XRF). X-rays can also be used to excite electrons in an object’s molecules to higher energy states. The radiation released as the molecules return to their original energy states is analyzed to determine the elemental composition of the surface of an object. This test is nondestructive since it does not require a sample.
X-RAY DIFFRACTION (XRD). X-rays are used to determine the crystalline composition of unknown materials. X-rays shot into a crystalline sample are reflected at angles characteristic of the crystal. The results are then readable on a piece of X-ray film or an electronic detector.
ELECTRON PROBE MICROANALYSIS. A microscopic sample is quantitatively analyzed for its major, minor, and trace elements. This form of analysis is used to study the composition of inorganic materials such as metals, stone, and glass.
GAS CHROMATOGRAPHY MASS SPECTROMETRY (GCMS). In this method of analysis, a material is identified by vaporizing a sample and then exposing it to strong electric and magnetic fields in order to separate and measure its components.