The use of Laser Ablation Spectrometry in the scientific analysis of Chinese ceramics.
Spectrometry – element an analysis based on a simple principle
Spectrometry has been around for at least half a century. It is an element analysis method based on the physics of different components (atoms) present. It uses the emitted electromagnetic waves (light waves) of elements for analyzing the chemical components of materials. It is based on the principle that chemical elements do emit electromagnetic waves (i.e. light waves) under certain conditions, whereas each element has its own unique wave length.
The principle of spectrometry is relatively simple and has been used for a long time for the component analysis of electrically conductive materials. It can be used for non-organic or mineral elements. With this analysis type the sample material is made to emit electromagnetic waves (e.g. in the form of light rays) and a spectroscope detects the different light waves present in the emitted light. As the different light waves in the spectre different represent chemical/mineral elements, the components of the sample material can thus be obtained.
This method iself is not new, but its application for analysing porcelain is relatively recent. Spectrometry has been used for many decades by the metalworking industry to analyze the components of metals. An electrode would be pointed at the metal sample and an electric charge would induce a spark to spring between electrode and metal sample. The light spectre of the spark would contain the wavelengths of the components present in the sample material, which were deteced by a spectroscope.
However, the spark method is not usable with ceramics due to their dïelectric (non-conductive) characteristics.
Laser ablation for use with ceramics As the electric discharge method described above can only be used with conductive materials, it is not suitable for porcelain and other ceramics. For this reason laser ablation is used instead to initiate the wave emission.
Laser ablation uses a different method to have the material emit the necessary electromagnetic waves. With laser ablation a laser beam is pointed unto the material to heat a tiny bit of material. The heat of the laser evaporates the material and changes it to plasma (turns from matter to gas, and is ionized), and the plasma can be used for measurement. The ions of the test material emit the required electromagnetic waves for the identification of each element by the spectroscope.
Application of Laser Ablation Spectrometry method for auhenticating antique ceramics
Laser ablation spectrometry was further developed for forensic purposes, in order to detect the relevant elements in fakes. It is today also used in archaeology. The tricky part is probably to acquire the data for analyzing the relevant material components for the individual kilns. A huge amount of shards that are reliably connected to the respective kilns needs will be necessary, in order to get data of all the hundreds of kilns. But, the analysis should be doable even if only shards or items from a limited number of major kiln sites are analyzed. Only in this case items from kilns without data cannot be positively identified.
Once reliable data are available, however, Laser Ablation Spectrometry should be fairly simple to clarify whether an item was made at the supposed kiln.
Possible factors affecting the results:
If the material composition of the clay or glaze did not differ much between different two or more kilns or periods, the material identity could only be limited to the concerned kilns as a whole.
If clay composition was not modified in a relevant manner throughout the time of existence of a kiln, the time of manufacture may not be decided accurately.
However, due to the large number of mineral/chemical elements analyzed with this method, it is likely there will be some differences in most cases, relevant or not. Download and view the report of a Laser Ablation Spectrometry research project.
