Scientific Authentication of Chinese Ceramics

There are currently two main methods used for scientific authentication of ceramics available:

  • Thermoluminescence Dating 
  • Spectrometric Analysis

Most authentication of antique Chinese porcelain and pottery is done by visual inspection, which not only requires a vast knowledge but also many years of experience.

Scientific methods are available but not widely used. Partially this is probably due to the relatively high cost involved. It may not be a good idea to do a scientific analysis costing more than the item itself.

However, forgers also have found methods to defeat these scientific authentication methods. So even if one is used to verify authenticity of an expensive item, it is still necessary to do a visual or hands-on inspection also. Multiple factors need to be examined always in addition to the scientific authentication/dating, in order to validate these if the result is positive.


Thermoluminescence dating (TL dating) is more suited for pottery than porcelain. It requires the removal of fairly large clay samples of approx. 3 mm diameter, which may destruct thin porcelain. Here is a link to Oxford Authentication Ltd. , which currently probably is the world's foremost provider of TL analysis. Read more about the principle of TL dating, and how forgers try to defeat this test.
This type of examination can only estimate the approximate age of a ceramic item.


Spectrometric analysis
Other scientific methods that are non-destructive are based mainly on elemental analysis of the material (clay or glaze); this is executed with the help of spectroscopy  (spectrometric analysis).
Spectroscopy is not a new testing method in material identification. In different forms it has been employed for decades by the industry for deciding material composition of metals.

The current methods suitable for ceramics do not need the grinding of holes into the material. The amount is either so minute, that it is invisible to the bare eye, or no material is required at all. That makes it more suitable for the finer porcelains.

One method is Laser Ablation Mass Spectrometry (LA-ICP-MS). In this case a laser is utilized to extract a minute amount of material. The trace of this in the material is so small that it is virtually invisible.
The other method uses X-rays (XRF, XRD analysis) to induce a secondary emission (fluorescence in the case of XRF). The emission shows the wave lengths of different chemical elements contained in the analyzed clay.

With spectroscopy the trace elements present in the clay or glaze of antique ceramics can be analyzed, and the result is then compared to sample data from different kiln sites and periods.
Once they fit, the period and location of production of a ceramic item is positively identified.
See more about elemental analysis and spectroscopy .

Download introduction to Laser Ablation ICP-MS    (courtesy E. Bartle)


Note:
There are rumours that expert forgers are catching up on spectrometric analysis methods too and are now sometimes adding the necessary mineral elements to the clay to fool the instruments. Thus, we may not be able to completely rely on this method alone in the future either.



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Antique Porcelain Appraisal

Spectrometry and its use with antique ceramics