Electron Miroprobe & X-Ray Flouresence

How It Works

Above are a sequence of events that happen to during X-ray fluorescence analysis. Each of these events is explained below in the order of which they occur.

1. X-Rays are generated by the equipment and directed at the material being tested. When X-Rays of sufficient energy strike an electron in an inner shell of an atom, that electron is ejected.
2. An electron from an outer shell then shifts to fill the gap in the inner shell. Electrons can shift from the adjacent orbit, or one even further away.
3. When the electron shifts orbits, an X-Ray photon is released. This photon has an energy which is characteristic of the element and electron shell shift.

Why And When To Use The Test

Depending on their location and hardness, samples may be cut with a jeweler's saw, diamond coated burr, or an emery cutting wheel. The sample is sealed in a plastic vial and labeled. Accompanying documentation includes a photo of the whole object, photo and description of the sample site, object description, dimensions and proposed age. Oxford Materials Characterization Services (Oxford, England) is equipped for EPMA and XRF analysis, as well as numerous other analytical techniques. A metallurgical examination is also performed on all samples analyzed by OMCS for TK. The work is generally supervised by Dr. Peter Northover.

Can you tell the difference between brass and bronze? How about 1000 year old brass and recycled artillery shells? Proper identification may be the key to detecting a forgery. Electron probe microanalysis (EPMA) and X-ray fluorescence (XRF) analysis can determine the composition of a metal sample. Used in conjunction with metallographic examination it may be possible to find evidence of antiquity, or the lack of it, in metal objects.

In addition to surface study and metallographic examination, the composition of a metal may provide tremendous information. The average composition of a metal can be determined by numerous methods. Databases exist which provide guidelines for the composition of Chinese bronzes of various ages. If an analyzed sample falls outside the normal parameters, it is not necessarily a forgery. Conversely, one within normal parameters is not necessarily authentic. For this reason, compositional analysis is not used alone, but is combined with metallographic and surface examination to detect evidence of antiquity, or the lack thereof.

Conclusion

Electron probe microanalysis (EPMA) and X-ray fluorescence (XRF) are both commonly used to determine the composition of archaeological materials. The data collected is seldom sufficient, in and of itself, to categorize a metallic object as antique or modern, and is generally used in conjunction with other forms of analysis and examination when studying purported artifacts.

Notes

1. On suitable samples, it can provide excellent evidence of age, just by itself. Used in conjunction with other examinations, it can provide evidence of authenticity of a gold object.


2. It can provide a date on objects as young as approximately 150 years in age, and as old as several thousand years. In the future, as the margin of error for the technique is improved, this should help identify copies made in antiquity, which are of historic interest, from modern forgeries.