Authenticating Ancient Chinese Jades Using Scientific Methods
By Janet G. Douglas
Many collectors and museums have questions relating to the authentication of ancient Chinese jades in light of the current market where forgeries are commonplace. Today’s forgers are producing convincing fakes, and it is becoming increasingly difficult to rely on one’s eye and knowledge.
It is only natural that people are looking to science for help.
In 1999, the catalog for a German auction of Chinese jades included scientific reports of authenticity of the items for sale. To the best of my knowledge, this was the first time
This was done. While this approach is a step in the right direction, jade collectors should know what science provides beyond a piece of paper deemed a certificate of authenticity.
Science can’t give definitive answers
At the risk of chipping at the pedestal on which some place the “scientific method,” jade collectors need to understand that scientific investigation cannot always provide black-and-white answers to jade authentication questions. The first, and probably most important, step in the authentication of a jade object should always be the thoughtful consideration of its art-historical context, as well as comparison with similar, preferably excavated, jades.
Nephrite jade incense burner
This incense burner is from the Tang Dynasty (circa 618-907).
This step is analogous to what a museum curator does when considering whether to purchase a piece. It is important to bear in mind, however, that this is also done by those in the lucrative business of jade forgery.
The challenge for the collector, then, is to look longer and more carefully than the forgers.
How does the jade compare in shape and decoration to those in excavated contexts and in well-documented museum collections? How does it compare, under close scrutiny, in workmanship? It is surprising how many forgeries can be uncovered by close examination and careful research. An educated jade collector is more likely to make good collecting decisions and avoid forgeries.
Lab work’s expensive
It is only after this first step that scientific investigation should be considered. Given the significant expense, the collector must feel comfortable with the validity of the results. Does the laboratory have a demonstrated history in the study and analysis of ancient Chinese jades? What is the specific question to be answered by the analysis? Is there data to support a given scientific technique showing that it is the most appropriate tool to answer a given question? Is there an opportunity to talk to the analyst to ensure that specific questions are answered?
Scientific methods to analyze and authenticate jades require a little ingenuity. For instance, no one will argue that ancient jades were worked using modern tools and techniques. But what does the presence of tool marks produced by hand tell you? It does not necessarily prove that the jade is ancient because it is entirely possible that a jade could be worked by hand today.
Similarly, we have to think carefully about surface accretions. Although a laboratory can identify residues of a mineral abrasive on the surface of a jade, it is far more difficult to determine when it was applied. Natural mineral abrasives used in ancient times are still readily available today, so their presence proves nothing.
Forgers able to fake jade’s appearance
The same is true of earthy accretions such as soil and calcareous encrustations. The clever forger, intending to simulate the appearance of burial and/or significant age, could easily add these to the surface of a jade.
White jade Buddha
This seated Buddha is from the Tang Dynasty (circa 618-907).
The use of natural alteration or “weathering” as proof of age is also difficult. Some scientists contend a jade with a weathered surface is at least a thousand years old because it takes this long for such a surface to develop. I’m not sure that research has been done to back that up. Any such research would need to take into account a variety of factors, such as porosity of the jade surface and the presence of deleterious substances in the burial environment, as well as water content and acidity (measured as pH).
A particular type of alteration known to occur on ancient Chinese jades, called “burial alteration,” consists of a selective dissolution (leaching) on a microscopic scale along mineral grain boundaries of solutions of high pH (pH> 9). This type of high pH environment can occur during decay of the corpse(s) with which the jades were buried.
Natural burial alteration may not take long
In one study, a piece of jade was placed in a bath of pH 10 for three months, after which the same type of alteration found on jades from ancient burials was seen to have occurred. Showed that “burial alteration” can take place within a relatively short time, and in the case of jades in ancient tombs, probably occurred during the months immediately after burial when the corpse(s) decomposed. Thus, it is entirely possible that this type of alteration can be achieved quite easily over a few months by a forger using a variety of artificial means.
There are other methods of treating the surfaces of jade artificially. Many of these treatments may elude detection by scientific method. This means the jade collector cannot rely solely on science to answer questions of authenticity. Nevertheless, scientific investigation can help by supplying additional information such as the identification and structure of materials on the surface of a jade, which can assist in the assessment of authenticity.
Green jade seal
A nephrite green-jade seal made between 1736 and 1795 during the Qinglong Period.
Nonetheless, clear-cut answers to questions of authenticity are still few and far between. Jade collectors must concern themselves with the serious study of excavated and other well-documented jades, and grapple with multiple explanations for what they observe. Yet that is partially what makes jade collecting so rewarding.
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