Is the external beam PIXE method suitable for determining ancient silver artifact fineness?

In archeometry, the non-destructive characteristic of an analytical method is always very attractive. For most of techniques, besides the need of sampling, difficulties can originate from the shape and the size of the silver artifacts to be analyzed. The external PIXE method should be an answer to this problem but several questions are arising from the implementation of the technique to such a material. The aim of this paper is to specify the experimental procedure as to take into account several parameters, which could induce dramatic errors. Among them it can be pointed out the superficial enrichment in silver, arising from the dissolution of copper and copper oxide, the surface roughness effects, the great importance of the stability of the geometric conditions. The accuracy and the precision of the method are considered within the scope of the results obtained in ancient times by the cupellation with ashbone cupels. In addition. the process involved to obtain silver alloys has been studied in order to define its influence on the real fineness of the objects. (C) 2000 Elsevier Science B.V. All rights reserved.