Scientific Authentication of Chinese Ceramics

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

• Thermoluminescence Dating
  
• Spectrometric Analysis

Today, the majority of authentications of antique Chinese porcelain and pottery is still done by visual inspection, which not only requires a vast knowledge but also many years of experience.
Visual inspection now also includes evaluating of glaze-internal ageing phenomena, which requires a microscope with significant magnification ratio.

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 scientific authentication methods. So even if one is used to verify authenticity of an expensive item type with scientific methods, it is still necessary to do an ocular or hands-on inspection additionally. Multiple factors need to be examined always in addition to the scientific authentication/dating methods, in order to validate these if the result is positive reagarding authenticity.

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 and is more suitable for an age of many hundred years.

Spectrometric analysis
Other scientific methods that are non-destructive are based mainly on elemental analysis of the material (clay or glaze); this analysis is executed with the help of spectroscopy  (spectrometric analysis).
Spectroscopy is not a new testing method. It has been used for material analysis for a long time for material testing in different forms iover decades by the industry. Spectrometric analyses decide the  material composition of materials, in this case the mineral clay naturally contains many different elements, which can help with the composition of the clay of kilns, rather than guessing age.

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

One method is Laser Ablation Inductively Coupled 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 spectrometry 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 .

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

XRF:
Download the treatise at this URL for more details.




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Antique Porcelain Appraisal

Spectrometry and its use with antique ceramics