Use of PIXE–PIGE under variable incident angle for ancient glass corrosion measurements

Although glass is usually considered as a very stable archaeological material, it can undergo severe degradation. Soda-lime glass, the most common glass throughout ancient times, is particularly sensitive to this problem. The glass surface absorbs moisture from its environment and the contact with CO2 causes Na2O and NaOH to convert to Na2CO3, which is extremely hygroscopic. The subsequent unstable glass layer can be leached out and causes decomposition of the glass. The non-destructive PIGE–PIXE method of investigation allows detection of this phenomenon even if no visible effect appears. The variable incident angle method is able to discern the depth of the degradation. One aim of such studies is the possible dating or at least fake detecting of archaeological materials. Furthermore, even objects of large size can be investigated with the atmospheric PIGE–PIXE set-up. Some examples of measurements on ancient glass are given. 2002 Elsevier Science B.V. All rights reserved. PACS: 82.80.Ej; 82.80.Yc